{
    Copyright (c) 1998-2002 by Florian Klaempfl

    This unit implements the first loading and searching of the modules

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

 ****************************************************************************
}
unit fppu;

{$i fpcdefs.inc}

{ $define DEBUG_UNIT_CRC_CHANGES}

{ close ppufiles on system that are
  short on file handles like DOS system PM }
{$ifdef GO32V2}
  {$define SHORT_ON_FILE_HANDLES}
{$endif GO32V2}
{$ifdef WATCOM}
  {$define SHORT_ON_FILE_HANDLES}
{$endif WATCOM}

interface

    uses
      cmsgs,verbose,
      cutils,cclasses,cstreams,
      globtype,globals,finput,fmodule,
      symbase,ppu,symtype;

    type
       { tppumodule }
       TAvailableUnitFile = (auPPU,auSrc);
       TAvailableUnitFiles = set of TAvailableUnitFile;

       tppumodule = class(tmodule)
          ppufile    : tcompilerppufile; { the PPU file }
          sourcefn   : TPathStr; { Source specified with "uses .. in '..'" }
          comments   : TCmdStrList;
          nsprefix   : TCmdStr; { Namespace prefix the unit was found with }
{$ifdef Test_Double_checksum}
          interface_read_crc_index,
          interface_write_crc_index,
          indirect_read_crc_index,
          indirect_write_crc_index,
          implementation_read_crc_index,
          implementation_write_crc_index : cardinal;
          interface_crc_array,
          indirect_crc_array,
          implementation_crc_array  : pointer;
{$endif def Test_Double_checksum}
          constructor create(LoadedFrom:TModule;const amodulename: string; const afilename:TPathStr;_is_unit:boolean);
          destructor destroy;override;
          procedure reset(for_recompile: boolean);override;
          procedure re_resolve(loadfrom: tmodule);
          function  openppufile:boolean;
          function  openppustream(strm:TCStream):boolean;
          procedure getppucrc;
          procedure writeppu;
          function loadppu(from_module : tmodule) : boolean;
          procedure post_load_or_compile(from_module : tmodule; second_time: boolean);
          procedure discardppu;
          function  needrecompile:boolean;
          procedure setdefgeneration;
          procedure reload_flagged_units;
          procedure end_of_parsing;override;
       private
          unitimportsymsderefs : tfplist;
         { Each time a unit's defs are (re)created, its defsgeneration is
           set to the value of a global counter, and the global counter is
           increased. We only reresolve its dependent units' defs in case
           they have been resolved only for an older generation, in order to
           avoid endless resolving loops in case of cyclic dependencies. }
          defsgeneration : longint;

          function check_loadfrompackage: boolean;
          procedure check_reload(from_module: tmodule; var do_load: boolean);
          function  openppu(ppufiletime:longint):boolean;
          procedure prepare_second_load(from_module: tmodule);
          procedure recompile_from_sources(from_module: tmodule);
          function  search_unit_files(loaded_from : tmodule; onlysource:boolean):TAvailableUnitFiles;
          function  search_unit(loaded_from : tmodule; onlysource,shortname:boolean):TAvailableUnitFiles;
          function  loadfrompackage:boolean;
          procedure load_interface;
          procedure load_implementation;
          procedure load_usedunits;
          procedure printcomments;
          procedure queuecomment(const s:TMsgStr;v,w:longint);
          procedure buildderefunitimportsyms;
          procedure derefunitimportsyms;
          procedure freederefunitimportsyms;
          procedure try_load_ppufile(from_module: tmodule);
          procedure writesourcefiles;
          procedure writeusedunit(intf:boolean);
          procedure writelinkcontainer(var p:tlinkcontainer;id:byte;strippath:boolean);
          procedure writederefmap;
          procedure writederefdata;
          procedure writeImportSymbols;
          procedure writeResources;
          procedure writeOrderedSymbols;
          procedure writeunitimportsyms;
          procedure writeasmsyms(kind:tunitasmlisttype;list:tfphashobjectlist);
          procedure writeextraheader;
          procedure readsourcefiles;
          procedure readloadunit;
          procedure readlinkcontainer(var p:tlinkcontainer);
          procedure readderefmap;
          procedure readderefdata;
          procedure readImportSymbols;
          procedure readResources;
          procedure readOrderedSymbols;
          procedure readwpofile;
          procedure readunitimportsyms;
          procedure readasmsyms;
          procedure readextraheader;
{$IFDEF MACRO_DIFF_HINT}
          procedure writeusedmacro(p:TNamedIndexItem;arg:pointer);
          procedure writeusedmacros;
          procedure readusedmacros;
{$ENDIF}
       end;

    function registerunit(callermodule:tmodule;const s : TIDString;const fn:string; out is_new:boolean) : tppumodule;


implementation

uses
  SysUtils,
  cfileutl,
  systems,version,options,
  symtable, symsym,
  wpoinfo,
  scanner,
  aasmbase,ogbase,
  parser,
  comphook,
  entfile,fpkg,fpcp;


var
  currentdefgeneration: longint;

{****************************************************************************
                                TPPUMODULE
 ****************************************************************************}

    constructor tppumodule.create(LoadedFrom:TModule;const amodulename: string; const afilename:TPathStr;_is_unit:boolean);
      begin
        inherited create(LoadedFrom,amodulename,afilename,_is_unit);
        ppufile:=nil;
        sourcefn:=afilename;
        unitimportsymsderefs:=tfplist.create;
      end;


    destructor tppumodule.destroy;
      begin
        discardppu;
        comments.free;
        comments:=nil;
        { all derefs allocated with new
          are dispose'd inside this method }
        freederefunitimportsyms;
        unitimportsymsderefs.free;
        unitimportsymsderefs:=nil;
        inherited Destroy;
      end;


    procedure tppumodule.reset(for_recompile : boolean);
      begin
        inc(currentdefgeneration);
        discardppu;
        freederefunitimportsyms;
        unitimportsymsderefs.free;
        unitimportsymsderefs:=tfplist.create;
        inherited reset(for_recompile);
      end;

    procedure tppumodule.re_resolve(loadfrom: tmodule);

      begin
        Message1(unit_u_reresolving_unit,modulename^);
        if tstoredsymtable(globalsymtable).is_deref_built then
          tstoredsymtable(globalsymtable).deref(false);
        if tstoredsymtable(globalsymtable).is_derefimpl_built then
          tstoredsymtable(globalsymtable).derefimpl(false);
        if assigned(localsymtable) then
          begin
            { we have only builderef(impl)'d the registered symbols of
              the localsymtable -> also only deref those again }
            if tstoredsymtable(localsymtable).is_deref_built then
              tstoredsymtable(localsymtable).deref(true);
            if tstoredsymtable(localsymtable).is_derefimpl_built then
              tstoredsymtable(localsymtable).derefimpl(true);
          end;
        if assigned(wpoinfo) then
          begin
            tunitwpoinfo(wpoinfo).deref;
            tunitwpoinfo(wpoinfo).derefimpl;
          end;

        { We have to flag the units that depend on this unit even
          though it didn't change, because they might also
          indirectly depend on the unit that did change (e.g.,
          in case rgobj, rgx86 and rgcpu have been compiled
          already, and then rgobj is recompiled for some reason
          -> rgx86 is re-reresolved, but the vmtentries of trgcpu
          must also be re-resolved, because they will also contain
          pointers to procdefs in the old trgobj (in case of a
          recompile, all old defs are freed) }
        flagdependent(loadfrom);
        reload_flagged_units;
      end;


    procedure tppumodule.queuecomment(const s:TMsgStr;v,w:longint);
    begin
      if comments = nil then
        comments := TCmdStrList.create;
      comments.insert(s);
    end;

    procedure tppumodule.printcomments;
    var
      comment: string;
    begin
      if comments = nil then
        exit;
      { comments are inserted in reverse order }
      repeat
        comment := comments.getlast;
        if length(comment) = 0 then
          exit;
        do_comment(v_normal, comment);
      until false;
    end;

    function tppumodule.openppufile:boolean;
      var
        ppufiletime : longint;
      begin
        openppufile:=false;
        Message1(unit_t_ppu_loading,ppufilename,@queuecomment);
      { Get ppufile time (also check if the file exists) }
        ppufiletime:=getnamedfiletime(ppufilename);
        if ppufiletime=-1 then
         exit;
      { Open the ppufile }
        Message1(unit_u_ppu_name,ppufilename);
        ppufile:=tcompilerppufile.create(ppufilename);
        if not ppufile.openfile then
         begin
           discardppu;
           Message(unit_u_ppu_file_too_short);
           exit;
         end;
        result:=openppu(ppufiletime);
      end;


    function tppumodule.openppustream(strm:TCStream):boolean;
      begin
        result:=false;
      { Open the ppufile }
        Message1(unit_u_ppu_name,ppufilename);
        ppufile:=tcompilerppufile.create(ppufilename);
        if not ppufile.openstream(strm) then
         begin
           discardppu;
           Message(unit_u_ppu_file_too_short);
           exit;
         end;
        result:=openppu(-1);
      end;


    function tppumodule.openppu(ppufiletime:longint):boolean;

      function checkheader: boolean;
        begin
          result:=false;
          { check for a valid PPU file }
            if not ppufile.CheckPPUId then
             begin
               Message(unit_u_ppu_invalid_header);
               exit;
             end;
          { check for allowed PPU versions }
            if not (ppufile.getversion = CurrentPPUVersion) then
             begin
               Message1(unit_u_ppu_invalid_version,tostr(ppufile.getversion),@queuecomment);
               exit;
             end;
          { check the target processor }
            if tsystemcpu(ppufile.header.common.cpu)<>target_cpu then
             begin
               Message(unit_u_ppu_invalid_processor,@queuecomment);
               exit;
             end;
          { check target }
            if tsystem(ppufile.header.common.target)<>target_info.system then
             begin
               Message(unit_u_ppu_invalid_target,@queuecomment);
               exit;
             end;
{$ifdef cpufpemu}
          { check if floating point emulation is on?
            fpu emulation isn't unit levelwise because it affects calling convention }
          if ((ppufile.header.common.flags and uf_fpu_emulation)<>0) <>
             (cs_fp_emulation in current_settings.moduleswitches) then
            begin
              Message(unit_u_ppu_invalid_fpumode,@queuecomment);
              exit;
            end;
{$endif cpufpemu}
           result:=true;
        end;

      function checkextraheader: boolean;
        begin
          result:=false;
          if ppufile.readentry<>ibextraheader then
            begin
              Message(unit_u_ppu_invalid_header);
              exit;
            end;
          readextraheader;
          if (longversion<>CurrentPPULongVersion) or
             not ppufile.EndOfEntry then
            begin
              Message(unit_u_ppu_invalid_header);
              exit;
            end;
{$ifdef i8086}
          { check i8086 memory model flags }
          if (mf_i8086_far_code in moduleflags) <>
             (current_settings.x86memorymodel in [mm_medium,mm_large,mm_huge]) then
            begin
              Message(unit_u_ppu_invalid_memory_model,@queuecomment);
              exit;
            end;
          if (mf_i8086_far_data in moduleflags) <>
             (current_settings.x86memorymodel in [mm_compact,mm_large]) then
            begin
              Message(unit_u_ppu_invalid_memory_model,@queuecomment);
              exit;
            end;
          if (mf_i8086_huge_data in moduleflags) <>
             (current_settings.x86memorymodel=mm_huge) then
            begin
              Message(unit_u_ppu_invalid_memory_model,@queuecomment);
              exit;
            end;
          if (mf_i8086_cs_equals_ds in moduleflags) <>
             (current_settings.x86memorymodel=mm_tiny) then
            begin
              Message(unit_u_ppu_invalid_memory_model,@queuecomment);
              exit;
            end;
          if (mf_i8086_ss_equals_ds in moduleflags) <>
             (current_settings.x86memorymodel in [mm_tiny,mm_small,mm_medium]) then
            begin
              Message(unit_u_ppu_invalid_memory_model,@queuecomment);
              exit;
            end;
{$endif i8086}
{$ifdef wasm}
          { check WebAssembly exceptions mode flag }
          if ((mf_wasm_no_exceptions in moduleflags) <>
              (ts_wasm_no_exceptions in current_settings.targetswitches)) or
             ((mf_wasm_bf_exceptions in moduleflags) <>
              (ts_wasm_bf_exceptions in current_settings.targetswitches)) or
             ((mf_wasm_js_exceptions in moduleflags) <>
              (ts_wasm_js_exceptions in current_settings.targetswitches)) or
             ((mf_wasm_native_exceptions in moduleflags) <>
              (ts_wasm_native_exceptions in current_settings.targetswitches)) then
            begin
              Message(unit_u_ppu_invalid_wasm_exceptions_mode,@queuecomment);
              exit;
            end;
          if (mf_wasm_threads in moduleflags) <>
             (ts_wasm_threads in current_settings.targetswitches) then
            begin
              Message(unit_u_ppu_wasm_threads_mismatch,@queuecomment);
              exit;
            end;
{$endif}
          if {$ifdef symansistr}not{$endif}(mf_symansistr in moduleflags) then
            begin
              Message(unit_u_ppu_symansistr_mismatch,@queuecomment);
              exit;
            end;
          if {$ifdef llvm}not{$endif}(mf_llvm in moduleflags) then
            begin
              Message(unit_u_ppu_llvm_mismatch,@queuecomment);
              exit;
            end;
          result:=true;
        end;

      begin
        openppu:=false;
        if not checkheader or
           not checkextraheader then
          begin
            discardppu;
            exit;
          end;

      { Load values to be access easier }
        headerflags:=ppufile.header.common.flags;
        crc:=ppufile.header.checksum;
        interface_crc:=ppufile.header.interface_checksum;
        indirect_crc:=ppufile.header.indirect_checksum;
        change_endian:=ppufile.change_endian;
      { Show Debug info }
        if ppufiletime<>-1 then
          Message1(unit_u_ppu_time,filetimestring(ppufiletime))
        else
          Message1(unit_u_ppu_time,'unknown');
        Message1(unit_u_ppu_flags,tostr(headerflags));
        Message1(unit_u_ppu_crc,hexstr(ppufile.header.checksum,8));
        Message1(unit_u_ppu_crc,hexstr(ppufile.header.interface_checksum,8)+' (intfc)');
        Message1(unit_u_ppu_crc,hexstr(ppufile.header.indirect_checksum,8)+' (indc)');
        Comment(V_used,'Number of definitions: '+tostr(ppufile.header.deflistsize));
        Comment(V_used,'Number of symbols: '+tostr(ppufile.header.symlistsize));
        openppu:=true;
      end;


    function tppumodule.search_unit_files(loaded_from : tmodule; onlysource:boolean):TAvailableUnitFiles;
      var
        found : TAvailableUnitFiles;
      begin
        found:=search_unit(loaded_from,onlysource,false);
        if (found=[]) and
           (ft83 in AllowedFilenameTransFormations) and
           (length(modulename^)>8) then
           found:=search_unit(loaded_from,onlysource,true);
        search_unit_files:=found;
      end;


    function tppumodule.search_unit(loaded_from : tmodule; onlysource,shortname:boolean):TAvailableUnitFiles;
      var
         singlepathstring,
         filename : TCmdStr;

         Function UnitExists(const ext:string;var foundfile:TCmdStr;const prefix:TCmdStr):boolean;
         var
           s : tcmdstr;
         begin
           if CheckVerbosity(V_Tried) then
             Message1(unit_t_unitsearch,Singlepathstring+filename+ext);
           s:=FileName+ext;
           if prefix<>'' then
             s:=prefix+'.'+s;
           UnitExists:=FindFile(s,Singlepathstring,true,foundfile);
         end;

         Function PPUSearchPath(const s,prefix:TCmdStr):boolean;
         var
           found : boolean;
           hs,
           newname : TCmdStr;
         begin
           Found:=false;
           singlepathstring:=FixPath(s,false);
         { Check for PPU file }
           Found:=UnitExists(target_info.unitext,hs,prefix);
           if Found then
            Begin
              SetFileName(hs,false);
              if prefix<>'' then
                begin
                  newname:=prefix+'.'+realmodulename^;
                  stringdispose(realmodulename);
                  realmodulename:=stringdup(newname);
                  stringdispose(modulename);
                  modulename:=stringdup(upper(newname));
                end;
              Found:=openppufile;
            End;
           PPUSearchPath:=Found;
         end;

         Function SourceSearchPath(const s,prefix:TCmdStr):boolean;
         var
           found   : boolean;
           hs,
           newname : TCmdStr;
         begin
           Found:=false;
           singlepathstring:=FixPath(s,false);
         { Check for Sources }
           ppufile:=nil;
           recompile_reason:=rr_noppu;
         {Check for .pp file}
           Found:=UnitExists(sourceext,hs,prefix);
           if not Found then
            begin
              { Check for .pas }
              Found:=UnitExists(pasext,hs,prefix);
            end;
           if not Found and
              ((m_mac in current_settings.modeswitches) or
               (tf_p_ext_support in target_info.flags)) then
            begin
              { Check for .p, if mode is macpas}
              Found:=UnitExists(pext,hs,prefix);
            end;
           mainsource:='';
           if Found then
            begin
              sources_avail:=true;
              { Load Filenames when found }
              mainsource:=hs;
              SetFileName(hs,false);
              if prefix<>'' then
                begin
                  newname:=prefix+'.'+realmodulename^;
                  stringdispose(realmodulename);
                  realmodulename:=stringdup(newname);
                  stringdispose(modulename);
                  modulename:=stringdup(upper(newname));
                end;
            end
           else
            sources_avail:=false;
           SourceSearchPath:=Found;
         end;

         Function SearchPath(const s,prefix:TCmdStr):TAvailableUnitFiles;
         var
           found : TAvailableUnitFiles;
         begin
           { First check for a ppu, then for the source }
           found:=[];
           if not onlysource then
             if PPUSearchPath(s,prefix) then
               Include(found,auPPU);
           if found=[] then
             if SourceSearchPath(s,prefix) then
              Include(found,auSrc);
           SearchPath:=found;
         end;

         Function SearchPathList(list:TSearchPathList;const prefix:TCmdStr):TAvailableUnitFiles;
         var
           hp : TCmdStrListItem;
           found : TAvailableUnitFiles;
         begin
           found:=[];
           hp:=TCmdStrListItem(list.First);
           while assigned(hp) do
            begin
              found:=SearchPath(hp.Str,prefix);
              if found<>[] then
               break;
              hp:=TCmdStrListItem(hp.next);
            end;
           SearchPathList:=found;
         end;

         function SearchPPUPaths(const prefix:TCmdStr):boolean;
         begin
           result:=PPUSearchPath('.',prefix);
           if (not result) and (outputpath<>'') then
            result:=PPUSearchPath(outputpath,prefix);
           if (not result) and Assigned(main_module) and (main_module.Path<>'')  then
            result:=PPUSearchPath(main_module.Path,prefix);
         end;

         function SearchSourcePaths(const prefix:TCmdStr):TAvailableUnitFiles;
         begin
           result:=[];
           if SourceSearchPath('.',prefix) then
              include(Result,auSrc);
           if (result=[]) and Assigned(main_module) and (main_module.Path<>'') then
             if SourceSearchPath(main_module.Path,prefix) then
              include(Result,auSrc);
           if (result=[]) and Assigned(loaded_from) then
             result:=SearchPathList(loaded_from.LocalUnitSearchPath,prefix);
           if (result=[]) then
             result:=SearchPathList(UnitSearchPath,prefix);
         end;

         function SearchNamespaceList(const prefixes:TCmdStrList): TAvailableUnitFiles;
         var
           nsitem : TCmdStrListItem;
           res : TAvailableUnitFiles;
         begin
           res:=[];
           nsitem:=TCmdStrListItem(prefixes.first);
           while assigned(nsitem) do
             begin
               if not onlysource then
                 begin
                   if SearchPPUPaths(nsitem.str) then
                     Include(res,auPPU);
                   if res<>[] then
                     break;
                 end;
               res:=SearchSourcePaths(nsitem.str);
               if res<>[] then
                 break;
               nsitem:=TCmdStrListItem(nsitem.next);
             end;
           if assigned(nsitem) then
             nsprefix:=nsitem.str;
           result:=res;
         end;


       var
         fnd : TAvailableUnitFiles;
         hs : TPathStr;
       begin
         fnd:=[];
         if shortname then
          filename:=FixFileName(Copy(realmodulename^,1,8))
         else
          filename:=FixFileName(realmodulename^);
         { try to find unit
            1. look for ppu in cwd
            2. look for ppu in outputpath if set, this is tp7 compatible (PFV)
            3. look for ppu in maindir
            4. look for the specified source file (from the uses line)
            5. look for source in cwd
            6. look for source in maindir
            7. local unit pathlist
            8. global unit pathlist
            9. for each default namespace:
                  repeat 1 - 3 and 5 - 8 with namespace as prefix }
         if not onlysource then
           if SearchPPUPaths('') then
             include(fnd,auPPU);
         if (fnd=[]) and (sourcefn<>'') then
          begin
            { the full filename is specified so we can't use here the
              searchpath (PFV) }
            if CheckVerbosity(V_Tried) then
              Message1(unit_t_unitsearch,ChangeFileExt(sourcefn,sourceext));
            if FindFile(ChangeFileExt(sourcefn,sourceext),'',true,hs) then
              include(fnd,auSrc);
            if (fnd=[]) then
             begin
               if CheckVerbosity(V_Tried) then
                 Message1(unit_t_unitsearch,ChangeFileExt(sourcefn,pasext));
               if FindFile(ChangeFileExt(sourcefn,pasext),'',true,hs) then
                 include(fnd,auSrc);
             end;
            if (fnd=[]) and
               ((m_mac in current_settings.modeswitches) or
                (tf_p_ext_support in target_info.flags)) then
             begin
               if CheckVerbosity(V_Tried) then
                 Message1(unit_t_unitsearch,ChangeFileExt(sourcefn,pext));
               if FindFile(ChangeFileExt(sourcefn,pext),'',true,hs) then
                include(fnd,auSrc)
             end;
            if [auSrc]=fnd then
             begin
               sources_avail:=true;
               state:=ms_compile;
               recompile_reason:=rr_noppu;
               mainsource:=hs;
               SetFileName(hs,false);
             end;
          end;
         if fnd=[] then
           begin
             fnd:=SearchSourcePaths('');
             // current_namespacelist is set to the current module's namespacelist.
             if (fnd=[]) and assigned(current_namespacelist) and (current_namespacelist.count>0) then
               fnd:=SearchNameSpaceList(current_namespacelist);
             if (fnd=[]) and (namespacelist.count>0) then
               fnd:=SearchNameSpaceList(namespacelist);
           end;
         search_unit:=fnd;
      end;

    function tppumodule.loadfrompackage: boolean;
      (*var
        singlepathstring,
        filename : TCmdStr;

        Function UnitExists(const ext:string;var foundfile:TCmdStr):boolean;
          begin
            if CheckVerbosity(V_Tried) then
              Message1(unit_t_unitsearch,Singlepathstring+filename);
            UnitExists:=FindFile(FileName,Singlepathstring,true,foundfile);
          end;

        Function PPUSearchPath(const s:TCmdStr):boolean;
          var
            found : boolean;
            hs    : TCmdStr;
          begin
            Found:=false;
            singlepathstring:=FixPath(s,false);
          { Check for PPU file }
            Found:=UnitExists(target_info.unitext,hs);
            if Found then
             Begin
               SetFileName(hs,false);
               //Found:=OpenPPU;
             End;
            PPUSearchPath:=Found;
          end;

        Function SearchPathList(list:TSearchPathList):boolean;
          var
            hp : TCmdStrListItem;
            found : boolean;
          begin
            found:=false;
            hp:=TCmdStrListItem(list.First);
            while assigned(hp) do
             begin
               found:=PPUSearchPath(hp.Str);
               if found then
                break;
               hp:=TCmdStrListItem(hp.next);
             end;
            SearchPathList:=found;
          end;*)

      var
        pkg : ppackageentry;
        pkgunit : pcontainedunit;
        i,idx : longint;
        strm : TCStream;
      begin
        result:=false;
        for i:=0 to packagelist.count-1 do
          begin
            pkg:=ppackageentry(packagelist[i]);
            if not assigned(pkg^.package) then
              internalerror(2013053103);
            idx:=pkg^.package.containedmodules.FindIndexOf(modulename^);
            if idx>=0 then
              begin
                { the unit is part of this package }
                pkgunit:=pcontainedunit(pkg^.package.containedmodules[idx]);
                if not assigned(pkgunit^.module) then
                  pkgunit^.module:=self;
                { ToDo: check whether we really don't need this anymore }
                {filename:=pkgunit^.ppufile;
                if not SearchPathList(unitsearchpath) then
                  exit};
                strm:=tpcppackage(pkg^.package).getmodulestream(self);
                if not assigned(strm) then
                  internalerror(2015103002);
                if not openppustream(strm) then
                  exit;
                package:=pkg^.package;
                Message2(unit_u_loading_from_package,modulename^,pkg^.package.packagename^);

                { now load the unit and all used units }
                load_interface;
                setdefgeneration;
                load_usedunits;
                Message1(unit_u_finished_loading_unit,modulename^);

                result:=true;
                break;
              end;
          end;
      end;


    procedure tppumodule.buildderefunitimportsyms;
      var
        i : longint;
        deref : pderef;
      begin
        unitimportsymsderefs.capacity:=unitimportsymsderefs.count+unitimportsyms.count;
        for i:=0 to unitimportsyms.count-1 do
          begin
            new(deref);
            deref^.build(unitimportsyms[i]);
            unitimportsymsderefs.add(deref);
          end;
      end;


    procedure tppumodule.derefunitimportsyms;
      var
        i : longint;
        sym : tsym;
      begin
        unitimportsyms.capacity:=unitimportsyms.count+unitimportsymsderefs.count;
        for i:=0 to unitimportsymsderefs.count-1 do
          begin
            sym:=tsym(pderef(unitimportsymsderefs[i])^.resolve);
            unitimportsyms.add(sym);
          end;
      end;

    procedure tppumodule.freederefunitimportsyms;
      var
        i : longint;
        deref : pderef;
      begin
        for i:=0 to unitimportsymsderefs.count-1 do
          begin
            deref:=pderef(unitimportsymsderefs[i]);
            system.dispose(deref);
          end;
      end;

{**********************************
    PPU Reading/Writing Helpers
***********************************}

{$IFDEF MACRO_DIFF_HINT}
    var
      is_initial: Boolean;

    procedure tppumodule.writeusedmacro(p:TNamedIndexItem;arg:pointer);
      begin
        if tmacro(p).is_used or is_initial then
          begin
            ppufile.putstring(p.name);
            ppufile.putboolean(is_initial);
            ppufile.putboolean(tmacro(p).is_used);
          end;
      end;

    procedure tppumodule.writeusedmacros;
      begin
        ppufile.do_crc:=false;
        is_initial:= true;
        initialmacrosymtable.foreach(@writeusedmacro,nil);
        is_initial:= false;
        if assigned(globalmacrosymtable) then
          globalmacrosymtable.foreach(@writeusedmacro,nil);
        localmacrosymtable.foreach(@writeusedmacro,nil);
        ppufile.writeentry(ibusedmacros);
        ppufile.do_crc:=true;
      end;
{$ENDIF}

    procedure tppumodule.writesourcefiles;
      var
        hp  : tinputfile;
        ifile : sizeint;
      begin
      { second write the used source files }
        ppufile.do_crc:=false;
      { write source files directly in good order }
        for ifile:=0 to sourcefiles.nfiles-1 do
          begin
            hp:=sourcefiles.files[ifile];
            ppufile.putstring(hp.inc_path+hp.name);
            ppufile.putlongint(hp.getfiletime);
         end;
        ppufile.writeentry(ibsourcefiles);
        ppufile.do_crc:=true;
      end;


    procedure tppumodule.writeusedunit(intf:boolean);
      var
        hp : tused_unit;
        oldcrc : boolean;
      begin
        { write a reference for each used unit }
        hp:=tused_unit(used_units.first);
        while assigned(hp) do
         begin
           if hp.in_interface=intf then
             begin
               ppufile.putstring(hp.u.realmodulename^);
               { the checksum should not affect the crc of this unit ! (PFV) }
               oldcrc:=ppufile.do_crc;
               ppufile.do_crc:=false;
               ppufile.putlongint(longint(hp.checksum));
               ppufile.putlongint(longint(hp.interface_checksum));
               ppufile.putlongint(longint(hp.indirect_checksum));
               ppufile.do_crc:=oldcrc;
               { combine all indirect checksums from units used by this unit }
               if intf then
                 ppufile.indirect_crc:=ppufile.indirect_crc xor hp.indirect_checksum;
             end;
           hp:=tused_unit(hp.next);
         end;
        ppufile.do_interface_crc:=true;
        ppufile.writeentry(ibloadunit);
      end;


    procedure tppumodule.writelinkcontainer(var p:tlinkcontainer;id:byte;strippath:boolean);
      var
        hcontainer : tlinkcontainer;
        s : TPathStr;
        mask : cardinal;
      begin
        hcontainer:=TLinkContainer.Create;
        while not p.empty do
         begin
           s:=p.get(mask);
           if strippath then
            ppufile.putstring(ExtractFileName(s))
           else
            ppufile.putstring(s);
           ppufile.putlongint(mask);
           hcontainer.add(s,mask);
         end;
        ppufile.writeentry(id);
        p.Free;
        p:=hcontainer;
      end;


    procedure tppumodule.writederefmap;
      var
        i : longint;
        oldcrc : boolean;
      begin
        { This does not influence crc }
        oldcrc:=ppufile.do_crc;
        ppufile.do_crc:=false;
        { The unit map used for resolving }
        ppufile.putlongint(derefmapcnt);
        for i:=0 to derefmapcnt-1 do
          begin
            if not assigned(derefmap[i].u) then
              internalerror(2005011512);
            ppufile.putstring(derefmap[i].u.modulename^)
          end;
        ppufile.writeentry(ibderefmap);
        ppufile.do_crc:=oldcrc;
      end;


    procedure tppumodule.writederefdata;
      var
        oldcrc : boolean;
        len,hlen : longint;
        buf : array[0..1023] of byte;
      begin
        if longword(derefdataintflen)>derefdata.size then
          internalerror(200310223);
        derefdata.seek(0);
        { Write interface data }
        len:=derefdataintflen;
        while (len>0) do
          begin
            if len>1024 then
              hlen:=1024
            else
              hlen:=len;
            derefdata.read(buf,hlen);
            ppufile.putdata(buf,hlen);
            dec(len,hlen);
          end;
        { Write implementation data, this does not influence crc }
        oldcrc:=ppufile.do_crc;
        ppufile.do_crc:=false;
        len:=derefdata.size-derefdataintflen;
        while (len>0) do
          begin
            if len>1024 then
              hlen:=1024
            else
              hlen:=len;
            derefdata.read(buf,hlen);
            ppufile.putdata(buf,hlen);
            dec(len,hlen);
          end;
        if derefdata.pos<>derefdata.size then
          internalerror(200310224);
        ppufile.do_crc:=oldcrc;
        ppufile.writeentry(ibderefdata);
      end;


    procedure tppumodule.writeImportSymbols;
      var
        i,j : longint;
        ImportLibrary : TImportLibrary;
        ImportSymbol  : TImportSymbol;
      begin
        for i:=0 to ImportLibraryList.Count-1 do
          begin
            ImportLibrary:=TImportLibrary(ImportLibraryList[i]);
            ppufile.putstring(ImportLibrary.Name);
            ppufile.putlongint(ImportLibrary.ImportSymbolList.Count);
            for j:=0 to ImportLibrary.ImportSymbolList.Count-1 do
              begin
                ImportSymbol:=TImportSymbol(ImportLibrary.ImportSymbolList[j]);
                ppufile.putstring(ImportSymbol.Name);
                ppufile.putstring(ImportSymbol.MangledName);
                ppufile.putlongint(ImportSymbol.OrdNr);
                ppufile.putbyte(byte(ImportSymbol.IsVar));
              end;
          end;
        ppufile.writeentry(ibImportSymbols);
      end;


    procedure tppumodule.writeResources;
      var
        res : TCmdStrListItem;
      begin
        res:=TCmdStrListItem(ResourceFiles.First);
        while res<>nil do
          begin
            ppufile.putstring(res.FPStr);
            res:=TCmdStrListItem(res.Next);
          end;
        ppufile.writeentry(ibresources);
      end;


    procedure tppumodule.writeOrderedSymbols;
      var
        res : TCmdStrListItem;
      begin
        res:=TCmdStrListItem(linkorderedsymbols.First);
        while res<>nil do
          begin
            ppufile.putstring(res.FPStr);
            res:=TCmdStrListItem(res.Next);
          end;
        ppufile.writeentry(iborderedsymbols);
      end;


    procedure tppumodule.writeunitimportsyms;
      var
        i : longint;
      begin
        ppufile.putlongint(unitimportsymsderefs.count);
        for i:=0 to unitimportsymsderefs.count-1 do
          ppufile.putderef(pderef(unitimportsymsderefs[i])^);
        ppufile.writeentry(ibunitimportsyms);
      end;


    procedure tppumodule.writeasmsyms(kind:tunitasmlisttype;list:tfphashobjectlist);
      var
        i : longint;
        sym : TAsmSymbol;
      begin
        ppufile.putbyte(ord(kind));
        ppufile.putlongint(list.count);
        for i:=0 to list.count-1 do
          begin
            sym:=TAsmSymbol(list[i]);
            ppufile.putstring(sym.Name);
            ppufile.putbyte(ord(sym.bind));
            ppufile.putbyte(ord(sym.typ));
          end;
        ppufile.writeentry(ibasmsymbols);
      end;

    procedure tppumodule.writeextraheader;
      var
        old_docrc: boolean;
      begin
        { create unit flags }
        if do_release then
          include(moduleflags,mf_release);
        if assigned(localsymtable) then
          include(moduleflags,mf_local_symtable);
        if cs_checkpointer_called in current_settings.moduleswitches then
          include(moduleflags,mf_checkpointer_called);
        if cs_compilesystem in current_settings.moduleswitches then
          include(moduleflags,mf_system_unit);
{$ifdef i8086}
        if current_settings.x86memorymodel in [mm_medium,mm_large,mm_huge] then
          include(moduleflags,mf_i8086_far_code);
        if current_settings.x86memorymodel in [mm_compact,mm_large] then
          include(moduleflags,mf_i8086_far_data);
        if current_settings.x86memorymodel=mm_huge then
          include(moduleflags,mf_i8086_huge_data);
        if current_settings.x86memorymodel=mm_tiny then
          include(moduleflags,mf_i8086_cs_equals_ds);
        if current_settings.x86memorymodel in [mm_tiny,mm_small,mm_medium] then
          include(moduleflags,mf_i8086_ss_equals_ds);
{$endif i8086}
{$ifdef wasm}
        if ts_wasm_no_exceptions in current_settings.targetswitches then
          include(moduleflags,mf_wasm_no_exceptions);
        if ts_wasm_native_exceptions in current_settings.targetswitches then
          include(moduleflags,mf_wasm_native_exceptions);
        if ts_wasm_js_exceptions in current_settings.targetswitches then
          include(moduleflags,mf_wasm_js_exceptions);
        if ts_wasm_bf_exceptions in current_settings.targetswitches then
          include(moduleflags,mf_wasm_bf_exceptions);
        if ts_wasm_threads in current_settings.targetswitches then
          include(moduleflags,mf_wasm_threads);
{$endif wasm}
{$ifdef llvm}
        include(moduleflags,mf_llvm);
{$endif}
{$ifdef symansistr}
        include(moduleflags,mf_symansistr);
{$endif}

        old_docrc:=ppufile.do_crc;
        ppufile.do_crc:=false;
        ppufile.putlongint(longint(CurrentPPULongVersion));
        ppufile.putset(tppuset4(moduleflags));
        ppufile.writeentry(ibextraheader);
        ppufile.do_crc:=old_docrc;
      end;


{$IFDEF MACRO_DIFF_HINT}

{
  Define MACRO_DIFF_HINT for the whole compiler (and ppudump)
  to turn this facility on. Also the hint messages defined
  below must be commented in in the msg/errore.msg file.

  There is some problems with this, thats why it is shut off:

  At the first compilation, consider a macro which is not initially
  defined, but it is used (e g the check that it is undefined is true).
  Since it do not exist, there is no macro object where the is_used
  flag can be set. Later on when the macro is defined, and the ppu
  is opened, the check cannot detect this.

  Also, in which macro object should this flag be set ? It cant be set
  for macros in the initialmacrosymboltable since this table is shared
  between different files.
}

    procedure tppumodule.readusedmacros;
      var
        hs : string;
        mac : tmacro;
        was_initial,
        was_used : boolean;
      {Reads macros which was defined or used when the module was compiled.
       This is done when a ppu file is open, before it possibly is parsed.}
      begin
        while not ppufile.endofentry do
         begin
           hs:=ppufile.getstring;
           was_initial:=ppufile.getboolean;
           was_used:=ppufile.getboolean;
           mac:=tmacro(initialmacrosymtable.Find(hs));
           if assigned(mac) then
             begin
{$ifndef EXTDEBUG}
           { if we don't have the sources why tell }
              if sources_avail then
{$endif ndef EXTDEBUG}
               if (not was_initial) and was_used then
                Message2(unit_h_cond_not_set_in_last_compile,hs,mainsource^);
             end
           else { not assigned }
             if was_initial and
                was_used then
              Message2(unit_h_cond_set_in_last_compile,hs,mainsource^);
         end;
      end;
{$ENDIF}

    procedure tppumodule.readsourcefiles;
      var
        temp,hs       : string;
        inc_path      : string;
        temp_dir      : TCmdStr;
        main_dir      : TCmdStr;
        found,
        is_main       : boolean;
        orgfiletime,
        source_time   : longint;
        hp            : tinputfile;
      begin
        sources_avail:=not(mf_release in moduleflags);
        is_main:=true;
        main_dir:='';
        while not ppufile.endofentry do
         begin
           hs:=SetDirSeparators(ppufile.getstring);
           inc_path:=ExtractFilePath(hs);
           orgfiletime:=ppufile.getlongint;
           temp_dir:='';
           if sources_avail then
             begin
               if (headerflags and uf_in_library)<>0 then
                begin
                  sources_avail:=false;
                  temp:=' library';
                end
               else if pos('Macro ',hs)=1 then
                begin
                  { we don't want to find this file }
                  { but there is a problem with file indexing !! }
                  temp:='';
                end
               else
                begin
                  { check the date of the source files:
                     1 path of sourcefn
                     2 path of ppu
                     3 path of main source
                     4 current dir
                     5 include/unit path }
                  found:=false;
                  if sourcefn<>'' then
                  begin
                    temp_dir:=ExtractFilePath(SetDirSeparators(sourcefn));
                    Source_Time:=GetNamedFileTime(temp_dir+hs);
                    if Source_Time<>-1 then
                      hs:=temp_dir+hs;
                  end else
                    Source_Time:=-1;
                  if Source_Time=-1 then
                    begin
                      Source_Time:=GetNamedFileTime(path+hs);
                      if Source_Time<>-1 then
                        hs:=path+hs
                      else
                       if not(is_main) then
                        begin
                          Source_Time:=GetNamedFileTime(main_dir+hs);
                          if Source_Time<>-1 then
                            hs:=main_dir+hs;
                        end;
                    end;
                  if Source_Time=-1 then
                    Source_Time:=GetNamedFileTime(hs);
                  if (Source_Time=-1) then
                    begin
                      if is_main then
                        found:=unitsearchpath.FindFile(hs,true,temp_dir)
                      else
                        found:=includesearchpath.FindFile(hs,true,temp_dir);
                      if found then
                       begin
                         Source_Time:=GetNamedFileTime(temp_dir);
                         if Source_Time<>-1 then
                          hs:=temp_dir;
                       end;
                    end;
                  if Source_Time<>-1 then
                    begin
                      if is_main then
                        main_dir:=ExtractFilePath(hs);
                      temp:=' time '+filetimestring(source_time);
                      if (orgfiletime<>-1) and
                         (source_time<>orgfiletime) then
                        begin
                          state:=ms_compile;
                          recompile_reason:=rr_sourcenewer;
                          Message2(unit_u_source_modified,hs,ppufilename,@queuecomment);
                          temp:=temp+' *';
                        end;
                    end
                  else
                    begin
                      sources_avail:=false;
                      temp:=' not found';
                    end;
                  hp:=tdosinputfile.create(hs);
                  hp.inc_path:=inc_path;
                  { the indexing is wrong here PM }
                  sourcefiles.register_file(hp);
                end;
             end
           else
             begin
               { still register the source module for proper error messages
                 since source_avail for the module is still false, this should not hurt }
               sourcefiles.register_file(tdosinputfile.create(hs));

               temp:=' not available';
             end;
           if is_main then
             begin
               mainsource:=hs;
             end;
           Message1(unit_u_ppu_source,hs+temp,@queuecomment);
           is_main:=false;
         end;
      { check if we want to rebuild every unit, only if the sources are
        available }
        if do_build and sources_avail then
          begin
             state:=ms_compile;
             recompile_reason:=rr_build;
          end;
      end;


    procedure tppumodule.readloadunit;
      var
        hs : string;
        pu : tused_unit;
        hp : tppumodule;
        indchecksum,
        intfchecksum,
        checksum : cardinal;
        isnew : boolean;

      begin

        while not ppufile.endofentry do
         begin
           hs:=ppufile.getstring;
           checksum:=cardinal(ppufile.getlongint);
           intfchecksum:=cardinal(ppufile.getlongint);
           indchecksum:=cardinal(ppufile.getlongint);
           { set the state of this unit before registering, this is
             needed for a correct circular dependency check }
           hp:=registerunit(self,hs,'',isnew);
           if isnew then
             usedunits.Concat(tused_unit.create(hp,in_interface,true,nil));
           if LoadCount=1 then
             pu:=addusedunit(hp,false,nil)
           else
             begin
             pu:=findusedunit(hp);
             { Safety, normally this should not happen:
               The used units list cannot change between loads unless recompiled and then loadcount is 1... }
             if pu=nil then
               pu:=addusedunit(hp,false,nil);
             end;
           pu.checksum:=checksum;
           pu.interface_checksum:=intfchecksum;
           pu.indirect_checksum:=indchecksum;
         end;
        in_interface:=false;
      end;


    procedure tppumodule.readlinkcontainer(var p:tlinkcontainer);
      var
        s : string;
        m : longint;
      begin
        while not ppufile.endofentry do
         begin
           s:=ppufile.getstring;
           m:=ppufile.getlongint;
           p.add(s,m);
         end;
      end;


    procedure tppumodule.readderefmap;
      var
        i : longint;
      begin
        { Load unit map used for resolving }
        derefmapsize:=ppufile.getlongint;
        derefmapcnt:=derefmapsize;
        setlength(derefmap,derefmapsize);
        for i:=0 to derefmapsize-1 do
          derefmap[i].modulename:=ppufile.getpshortstring;
      end;


    procedure tppumodule.readderefdata;
      var
        len,hlen : longint;
        buf : array[0..1023] of byte;
      begin
        len:=ppufile.entrysize;
        while (len>0) do
          begin
            if len>1024 then
              hlen:=1024
            else
              hlen:=len;
            ppufile.getdata(buf,hlen);
            derefdata.write(buf,hlen);
            dec(len,hlen);
          end;
      end;


    procedure tppumodule.readImportSymbols;
      var
        j,
        extsymcnt   : longint;
        ImportLibrary  : TImportLibrary;
        extsymname  : string;
        extsymmangledname : string;
        extsymordnr : longint;
        extsymisvar : boolean;
      begin
        while not ppufile.endofentry do
          begin
            ImportLibrary:=TImportLibrary.Create(ImportLibraryList,ppufile.getstring);
            extsymcnt:=ppufile.getlongint;
            for j:=0 to extsymcnt-1 do
              begin
                extsymname:=ppufile.getstring;
                extsymmangledname:=ppufile.getstring;
                extsymordnr:=ppufile.getlongint;
                extsymisvar:=(ppufile.getbyte<>0);
                TImportSymbol.Create(ImportLibrary.ImportSymbolList,extsymname,
                  extsymmangledname,extsymordnr,extsymisvar);
              end;
          end;
      end;


    procedure tppumodule.readResources;
      begin
        while not ppufile.endofentry do
          resourcefiles.Insert(ppufile.getstring);
      end;


    procedure tppumodule.readOrderedSymbols;
      begin
        while not ppufile.endofentry do
          linkorderedsymbols.Concat(ppufile.getstring);
      end;


    procedure tppumodule.readwpofile;
      var
        orgwpofilename: string;
        orgwpofiletime: longint;
      begin
        { check whether we are using the same wpo feedback input file as when
          this unit was compiled (same file name and file date)
        }
        orgwpofilename:=ppufile.getstring;
        orgwpofiletime:=ppufile.getlongint;
        if (extractfilename(orgwpofilename)<>extractfilename(wpofeedbackinput)) or
           (orgwpofiletime<>GetNamedFileTime(orgwpofilename)) then
          { make sure we don't throw away a precompiled unit if the user simply
            forgot to specify the right wpo feedback file
          }
          message3(unit_e_different_wpo_file,ppufilename,orgwpofilename,filetimestring(orgwpofiletime));
      end;


    procedure tppumodule.readunitimportsyms;
      var
        c,i : longint;
        deref : pderef;
      begin
        c:=ppufile.getlongint;
        for i:=0 to c-1 do
          begin
            new(deref);
            ppufile.getderef(deref^);
            unitimportsymsderefs.add(deref);
          end;
      end;


    procedure tppumodule.readasmsyms;
      var
        c,i : longint;
        name : TSymStr;
        bind : TAsmsymbind;
        typ : TAsmsymtype;
        list : tfphashobjectlist;
      begin
        case tunitasmlisttype(ppufile.getbyte) of
          ualt_public:
            list:=publicasmsyms;
          ualt_extern:
            list:=externasmsyms;
        end;
        c:=ppufile.getlongint;
        for i:=0 to c-1 do
          begin
            name:=ppufile.getstring;
            bind:=TAsmsymbind(ppufile.getbyte);
            typ:=TAsmsymtype(ppufile.getbyte);
            TAsmSymbol.Create(list,name,bind,typ);
          end;
      end;


    procedure tppumodule.readextraheader;
      begin
        longversion:=cardinal(ppufile.getlongint);
        ppufile.getset(tppuset4(moduleflags));
      end;


    procedure tppumodule.load_interface;
      var
        b : byte;
        newmodulename : string;
      begin
       { read interface part }
         repeat
           b:=ppufile.readentry;
           case b of
             ibjvmnamespace :
               begin
                 namespace:=ppufile.getpshortstring;
               end;
             ibmodulename :
               begin
                 newmodulename:=ppufile.getstring;
                 if (cs_check_unit_name in current_settings.globalswitches) and
                    (upper(newmodulename)<>modulename^) then
                   Message2(unit_f_unit_name_error,realmodulename^,newmodulename);
                 stringdispose(modulename);
                 stringdispose(realmodulename);
                 modulename:=stringdup(upper(newmodulename));
                 realmodulename:=stringdup(newmodulename);
               end;
             ibextraheader:
               begin
                 readextraheader;
               end;
             ibfeatures :
               begin
                 ppufile.getset(tppuset4(features));
               end;
             ibmoduleoptions:
               begin
                 ppufile.getset(tppuset1(moduleoptions));
                 if mo_has_deprecated_msg in moduleoptions then
                   begin
                     stringdispose(deprecatedmsg);
                     deprecatedmsg:=ppufile.getpshortstring;
                   end;
               end;
             ibsourcefiles :
               readsourcefiles;
{$IFDEF MACRO_DIFF_HINT}
             ibusedmacros :
               readusedmacros;
{$ENDIF}
             ibloadunit :
               readloadunit;
             iblinkunitofiles :
               readlinkcontainer(LinkUnitOFiles);
             iblinkunitstaticlibs :
               readlinkcontainer(LinkUnitStaticLibs);
             iblinkunitsharedlibs :
               readlinkcontainer(LinkUnitSharedLibs);
             iblinkotherofiles :
               readlinkcontainer(LinkotherOFiles);
             iblinkotherstaticlibs :
               readlinkcontainer(LinkotherStaticLibs);
             iblinkothersharedlibs :
               readlinkcontainer(LinkotherSharedLibs);
             iblinkotherframeworks :
               readlinkcontainer(LinkOtherFrameworks);
             ibmainname:
               begin
                 mainname:=ppufile.getpshortstring;
                 if (mainaliasname<>defaultmainaliasname) then
                   Message1(scan_w_multiple_main_name_overrides,mainaliasname);
                 mainaliasname:=mainname^;
               end;
             ibImportSymbols :
               readImportSymbols;
             ibderefmap :
               readderefmap;
             ibderefdata :
               readderefdata;
             ibresources:
               readResources;
             iborderedsymbols:
               readOrderedSymbols;
             ibwpofile:
               readwpofile;
             ibendinterface :
               break;
           else
             Message1(unit_f_ppu_invalid_entry,tostr(b));
           end;
           { we can already stop when we know that we must recompile }
           if state=ms_compile then
             exit;
         until false;
      end;


    procedure tppumodule.load_implementation;
      var
        b : byte;
      begin
         { read implementation part }
         repeat
           b:=ppufile.readentry;
           case b of
             ibloadunit :
               readloadunit;
             ibasmsymbols :
               readasmsyms;
             ibunitimportsyms:
               readunitimportsyms;
             ibendimplementation :
               break;
           else
             Message1(unit_f_ppu_invalid_entry,tostr(b));
           end;
         until false;
      end;


    procedure tppumodule.writeppu;
      begin
         Message1(unit_u_ppu_write,realmodulename^);

         { create unit flags }
{$ifdef cpufpemu}
         if (cs_fp_emulation in current_settings.moduleswitches) then
           headerflags:=headerflags or uf_fpu_emulation;
{$endif cpufpemu}
         { create new ppufile }
         ppufile:=tcompilerppufile.create(ppufilename);
         if not ppufile.createfile then
          Message(unit_f_ppu_cannot_write);

{$ifdef Test_Double_checksum_write}
         { Re-use the values collected in .INT part }
         if assigned(interface_crc_array) then
           begin
             ppufile.implementation_write_crc_index:=implementation_write_crc_index;
             ppufile.interface_write_crc_index:=interface_write_crc_index;
             ppufile.indirect_write_crc_index:=indirect_write_crc_index;
             if assigned(ppufile.interface_crc_array) then
               begin
                 dispose(ppufile.interface_crc_array);
                 ppufile.interface_crc_array:=interface_crc_array;
               end; 
             if assigned(ppufile.implementation_crc_array) then
               begin
                 dispose(ppufile.implementation_crc_array);
                 ppufile.implementation_crc_array:=implementation_crc_array;
               end; 
             if assigned(ppufile.indirect_crc_array) then
               begin
                 dispose(ppufile.indirect_crc_array);
                 ppufile.indirect_crc_array:=indirect_crc_array;
               end; 
           end;
         if FileExists(ppufilename+'.IMP',false) then
           RenameFile(ppufilename+'.IMP',ppufilename+'.IMP-old');
         Assign(ppufile.CRCFile,ppufilename+'.IMP');
         Rewrite(ppufile.CRCFile);
         Writeln(ppufile.CRCFile,'CRC in writeppu method of implementation of ',ppufilename,' defsgeneration=',defsgeneration);
{$endif def Test_Double_checksum_write}

         { extra header (sub version, module flags) }
         writeextraheader;

         { first the (JVM) namespace }
         if assigned(namespace) then
           begin
             ppufile.putstring(namespace^);
             ppufile.writeentry(ibjvmnamespace);
           end;
         { the unitname }
         ppufile.putstring(realmodulename^);
         ppufile.writeentry(ibmodulename);

         ppufile.putset(tppuset1(moduleoptions));
         if mo_has_deprecated_msg in moduleoptions then
           ppufile.putstring(deprecatedmsg^);
         ppufile.writeentry(ibmoduleoptions);

         { write the alternate main procedure name if any }
         if assigned(mainname) then
           begin
             ppufile.putstring(mainname^);
             ppufile.writeentry(ibmainname);
           end;

         if cs_compilesystem in current_settings.moduleswitches then
           begin
             ppufile.putset(tppuset4(features));
             ppufile.writeentry(ibfeatures);
           end;

         writesourcefiles;
{$IFDEF MACRO_DIFF_HINT}
         writeusedmacros;
{$ENDIF}

         { write interface uses }
         writeusedunit(true);

         { write the objectfiles and libraries that come for this unit,
           preserve the containers because they are still needed to load
           the link.res.
            All doesn't depend on the crc! It doesn't matter
           if a unit is in a .o or .a file }
         ppufile.do_crc:=false;
         { write after source files, so that we know whether or not the compiler
           will recompile the unit when checking whether the correct wpo file is
           used (if it will recompile the unit anyway, it doesn't matter)
         }
         if (wpofeedbackinput<>'') then
           begin
             ppufile.putstring(wpofeedbackinput);
             ppufile.putlongint(getnamedfiletime(wpofeedbackinput));
             ppufile.writeentry(ibwpofile);
           end;
         writelinkcontainer(linkunitofiles,iblinkunitofiles,true);
         writelinkcontainer(linkunitstaticlibs,iblinkunitstaticlibs,true);
         writelinkcontainer(linkunitsharedlibs,iblinkunitsharedlibs,true);
         writelinkcontainer(linkotherofiles,iblinkotherofiles,false);
         writelinkcontainer(linkotherstaticlibs,iblinkotherstaticlibs,true);
         writelinkcontainer(linkothersharedlibs,iblinkothersharedlibs,true);
         writelinkcontainer(linkotherframeworks,iblinkotherframeworks,true);
         writeImportSymbols;
         writeResources;
         writeOrderedSymbols;
         ppufile.do_crc:=true;

         { generate implementation deref data, the interface deref data is
           already generated when calculating the interface crc }
         if (cs_compilesystem in current_settings.moduleswitches) then
           begin
             tstoredsymtable(globalsymtable).buildderef;
             derefdataintflen:=derefdata.size;
           end
         else
           { the unit may have been re-resolved, in which case the current
             position in derefdata is not necessarily at the end }
            derefdata.seek(derefdata.size);
         tstoredsymtable(globalsymtable).buildderefimpl;
         tunitwpoinfo(wpoinfo).buildderef;
         tunitwpoinfo(wpoinfo).buildderefimpl;

         if assigned(globalmacrosymtable) and (globalmacrosymtable.SymList.count > 0) then
            begin
              tstoredsymtable(globalmacrosymtable).buildderef;
              tstoredsymtable(globalmacrosymtable).buildderefimpl;
            end;

         if mf_local_symtable in moduleflags then
           tstoredsymtable(localsymtable).buildderef_registered;
         buildderefunitimportsyms;
         writederefmap;
         writederefdata;

         ppufile.writeentry(ibendinterface);

         { write the symtable entries }
         tstoredsymtable(globalsymtable).ppuwrite(ppufile);

         if assigned(globalmacrosymtable) and (globalmacrosymtable.SymList.count > 0) then
           begin
             ppufile.putbyte(byte(true));
             ppufile.writeentry(ibexportedmacros);
             tstoredsymtable(globalmacrosymtable).ppuwrite(ppufile);
           end
         else
           begin
             ppufile.putbyte(byte(false));
             ppufile.writeentry(ibexportedmacros);
           end;

         { everything after this doesn't affect the crc }
         ppufile.do_crc:=false;

         { write implementation uses }
         writeusedunit(false);

         { write all public assembler symbols }
         writeasmsyms(ualt_public,publicasmsyms);

         { write all external assembler symbols }
         writeasmsyms(ualt_extern,externasmsyms);

         { write all symbols imported from another unit }
         writeunitimportsyms;

         { end of implementation }
         ppufile.writeentry(ibendimplementation);

         { write static symtable
           needed for local debugging of unit functions }
         if mf_local_symtable in moduleflags then
           tstoredsymtable(localsymtable).ppuwrite(ppufile);

         { write whole program optimisation-related information }
         tunitwpoinfo(wpoinfo).ppuwrite(ppufile);

         { the last entry ibend is written automatically }

         { flush to be sure }
         ppufile.flush;
         { create and write header }
         ppufile.header.common.size:=ppufile.size;
         ppufile.header.checksum:=ppufile.crc;
         ppufile.header.interface_checksum:=ppufile.interface_crc;
         ppufile.header.indirect_checksum:=ppufile.indirect_crc;
         ppufile.header.common.compiler:=wordversion;
         ppufile.header.common.cpu:=word(target_cpu);
         ppufile.header.common.target:=word(target_info.system);
         ppufile.header.common.flags:=headerflags;
         ppufile.header.deflistsize:=current_module.deflist.count;
         ppufile.header.symlistsize:=current_module.symlist.count;
         ppufile.writeheader;

         { save crc in current module also }
         crc:=ppufile.crc;
         interface_crc:=ppufile.interface_crc;
         indirect_crc:=ppufile.indirect_crc;

{$ifdef Test_Double_checksum_write}
         Writeln(ppufile.CRCFile,'End of implementation CRC in writeppu method of ',ppufilename,
                 ' implementation_crc=$',hexstr(ppufile.crc,8),
                 ' interface_crc=$',hexstr(ppufile.interface_crc,8),
                 ' indirect_crc=$',hexstr(ppufile.indirect_crc,8),
                 ' implementation_crc_size=',ppufile.implementation_read_crc_index,
                 ' interface_crc_size=',ppufile.interface_read_crc_index,
                 ' indirect_crc_size=',ppufile.indirect_read_crc_index,
                 ' defsgeneration=',defsgeneration);
         close(ppufile.CRCFile);
{$endif Test_Double_checksum_write}

         discardppu;
      end;


    procedure tppumodule.getppucrc;
      begin

         { create new ppufile }
         ppufile:=tcompilerppufile.create(ppufilename);
         ppufile.crc_only:=true;
         if not ppufile.createfile then
           Message(unit_f_ppu_cannot_write);

{$ifdef Test_Double_checksum_write}
         if FileExists(ppufilename+'.INT',false) then
           RenameFile(ppufilename+'.INT',ppufilename+'.INT-old');
         Assign(ppufile.CRCFile,ppufilename+'.INT');
         Rewrite(ppufile.CRCFile);
         Writeln(ppufile.CRCFile,'CRC of getppucrc of ',ppufilename,
                 ' defsgeneration=',defsgeneration);
{$endif def Test_Double_checksum_write}
         { first the (JVM) namespace }
         if assigned(namespace) then
           begin
             ppufile.putstring(namespace^);
             ppufile.writeentry(ibjvmnamespace);
           end;
         { the unitname }
         ppufile.putstring(realmodulename^);
         ppufile.writeentry(ibmodulename);

         { extra header (sub version, module flags) }
         writeextraheader;

         ppufile.putset(tppuset1(moduleoptions));
         if mo_has_deprecated_msg in moduleoptions then
           ppufile.putstring(deprecatedmsg^);
         ppufile.writeentry(ibmoduleoptions);

         { the interface units affect the crc }
         writeusedunit(true);

         { deref data of interface that affect the crc }
         derefdata.reset;
         tstoredsymtable(globalsymtable).buildderef;
         derefdataintflen:=derefdata.size;
         writederefmap;
         writederefdata;

         ppufile.writeentry(ibendinterface);

         { write the symtable entries }
         tstoredsymtable(globalsymtable).ppuwrite(ppufile);

         if assigned(globalmacrosymtable) and (globalmacrosymtable.SymList.count > 0) then
           begin
             ppufile.putbyte(byte(true));
             ppufile.writeentry(ibexportedmacros);
             tstoredsymtable(globalmacrosymtable).ppuwrite(ppufile);
           end
         else
           begin
             ppufile.putbyte(byte(false));
             ppufile.writeentry(ibexportedmacros);
           end;

         { save crc  }
         crc:=ppufile.crc;
         interface_crc:=ppufile.interface_crc;
         indirect_crc:=ppufile.indirect_crc;

         { end of implementation, to generate a correct ppufile
           for ppudump when using DEBUG_GENERATE_INTERFACE_PPU define }
         ppufile.writeentry(ibendimplementation);

{$ifdef Test_Double_checksum_write}
         Writeln(ppufile.CRCFile,'End of CRC of getppucrc of ',ppufilename,
                 ' implementation_crc=$',hexstr(ppufile.crc,8),
                 ' interface_crc=$',hexstr(ppufile.interface_crc,8),
                 ' indirect_crc=$',hexstr(ppufile.indirect_crc,8),
                 ' implementation_crc_size=',ppufile.implementation_write_crc_index,
                 ' interface_crc_size=',ppufile.interface_write_crc_index,
                 ' indirect_crc_size=',ppufile.indirect_write_crc_index,
                 ' defsgeneration=',defsgeneration);
         close(ppufile.CRCFile);
         { Remember the values generated in .INT part }
          implementation_write_crc_index:=ppufile.implementation_write_crc_index;
          interface_write_crc_index:=ppufile.interface_write_crc_index;
          indirect_write_crc_index:=ppufile.indirect_write_crc_index;
          interface_crc_array:=ppufile.interface_crc_array;
          ppufile.interface_crc_array:=nil;
          implementation_crc_array:=ppufile.implementation_crc_array;
          ppufile.implementation_crc_array:=nil;
          indirect_crc_array:=ppufile.indirect_crc_array;
          ppufile.indirect_crc_array:=nil;
{$endif Test_Double_checksum_write}

         { create and write header, this will only be used
           for debugging purposes }
         ppufile.header.common.size:=ppufile.size;
         ppufile.header.checksum:=ppufile.crc;
         ppufile.header.interface_checksum:=ppufile.interface_crc;
         ppufile.header.indirect_checksum:=ppufile.indirect_crc;
         ppufile.header.common.compiler:=wordversion;
         ppufile.header.common.cpu:=word(target_cpu);
         ppufile.header.common.target:=word(target_info.system);
         ppufile.header.common.flags:=headerflags;
         ppufile.writeheader;

         discardppu;
      end;


    procedure tppumodule.load_usedunits;
      var
        pu           : tused_unit;
      begin
        if current_module<>self then
         internalerror(200212284);
        { load the used units from interface }
        in_interface:=true;
        pu:=tused_unit(used_units.first);
        while assigned(pu) do
         begin
           if pu.in_interface then
            begin
              tppumodule(pu.u).loadppu(self);
              { if this unit is scheduled for compilation or compiled we can stop }
              if state in [ms_compile,ms_compiled,ms_processed] then
               exit;
              { add this unit to the dependencies }
              pu.u.adddependency(self,true);
              { need to recompile the current unit, check the interface
                crc. And when not compiled with -Ur then check the complete
                crc }
              if (pu.u.interface_crc<>pu.interface_checksum) or
                 (pu.u.indirect_crc<>pu.indirect_checksum) or
                 (
                  (not(mf_release in moduleflags)) and
                  (pu.u.crc<>pu.checksum)
                 ) then
               begin
                 Message2(unit_u_recompile_crc_change,realmodulename^,pu.u.ppufilename,@queuecomment);
{$ifdef DEBUG_UNIT_CRC_CHANGES}
                 if (pu.u.interface_crc<>pu.interface_checksum) then
                   Comment(V_Normal,'  intfcrc change: '+hexstr(pu.u.interface_crc,8)+' for '+pu.u.ppufilename+' <> '+hexstr(pu.interface_checksum,8)+' in unit '+realmodulename^)
                 else if (pu.u.indirect_crc<>pu.indirect_checksum) then
                   Comment(V_Normal,'  indcrc change: '+hexstr(pu.u.indirect_crc,8)+' for '+pu.u.ppufilename+' <> '+hexstr(pu.indirect_checksum,8)+' in unit '+realmodulename^)
                 else
                   Comment(V_Normal,'  implcrc change: '+hexstr(pu.u.crc,8)+' for '+pu.u.ppufilename+' <> '+hexstr(pu.checksum,8)+' in unit '+realmodulename^);
{$endif DEBUG_UNIT_CRC_CHANGES}
                 recompile_reason:=rr_crcchanged;
                 state:=ms_compile;
                 exit;
               end;
            end;
           pu:=tused_unit(pu.next);
         end;
        { ok, now load the interface of this unit }
        if current_module<>self then
         internalerror(200208187);
        deflist.count:=ppufile.header.deflistsize;
        symlist.count:=ppufile.header.symlistsize;
        globalsymtable:=tglobalsymtable.create(modulename^,moduleid);
        tstoredsymtable(globalsymtable).ppuload(ppufile);

        if ppufile.readentry<>ibexportedmacros then
          Message(unit_f_ppu_read_error);
        if boolean(ppufile.getbyte) then
          begin
            globalmacrosymtable:=tmacrosymtable.Create(true);
            tstoredsymtable(globalmacrosymtable).ppuload(ppufile)
          end;

        interface_compiled:=true;

        { read the implementation part, containing
          the implementation uses and ObjData }
        in_interface:=false;
        load_implementation;

        { now only read the implementation uses }
        pu:=tused_unit(used_units.first);
        while assigned(pu) do
         begin
           if (not pu.in_interface) then
            begin
              tppumodule(pu.u).loadppu(self);
              { if this unit is compiled we can stop }
              if state=ms_compiled then
               exit;
              { add this unit to the dependencies }
              pu.u.adddependency(self,false);
              { need to recompile the current unit ? }
              if (pu.u.interface_crc<>pu.interface_checksum) or
                 (pu.u.indirect_crc<>pu.indirect_checksum) then
                begin
                  Message2(unit_u_recompile_crc_change,realmodulename^,pu.u.ppufilename+' {impl}',@queuecomment);
{$ifdef DEBUG_UNIT_CRC_CHANGES}
                  if (pu.u.interface_crc<>pu.interface_checksum) then
                    Comment(V_Normal,'  intfcrc change (2): '+hexstr(pu.u.interface_crc,8)+' for '+pu.u.ppufilename+' <> '+hexstr(pu.interface_checksum,8)+' in unit '+realmodulename^)
                  else if (pu.u.indirect_crc<>pu.indirect_checksum) then
                    Comment(V_Normal,'  indcrc change (2): '+hexstr(pu.u.indirect_crc,8)+' for '+pu.u.ppufilename+' <> '+hexstr(pu.indirect_checksum,8)+' in unit '+realmodulename^);
{$endif DEBUG_UNIT_CRC_CHANGES}
                  recompile_reason:=rr_crcchanged;
                  state:=ms_compile;
                  exit;
                end;
            end;
           pu:=tused_unit(pu.next);
         end;

        { load implementation symtable }
        if mf_local_symtable in moduleflags then
          begin
            localsymtable:=tstaticsymtable.create(modulename^,moduleid);
            tstaticsymtable(localsymtable).ppuload(ppufile);
          end;

        { we can now derefence all pointers to the implementation parts }
        tstoredsymtable(globalsymtable).derefimpl(false);
        { we've just loaded the localsymtable from the ppu file, so everything
          in it was registered by definition (otherwise it wouldn't have been in
          there) }
        if assigned(localsymtable) then
          tstoredsymtable(localsymtable).derefimpl(false);

        derefunitimportsyms;

         { read whole program optimisation-related information }
         wpoinfo:=tunitwpoinfo.ppuload(ppufile);
         tunitwpoinfo(wpoinfo).deref;
         tunitwpoinfo(wpoinfo).derefimpl;
      end;


    function tppumodule.needrecompile:boolean;
      var
        pu : tused_unit;
      begin
        result:=false;
        pu:=tused_unit(used_units.first);
        while assigned(pu) do
         begin
           { need to recompile the current unit, check the interface
             crc. And when not compiled with -Ur then check the complete
             crc }
           if (pu.u.interface_crc<>pu.interface_checksum) or
              (pu.u.indirect_crc<>pu.indirect_checksum) or
              (
               (pu.in_interface) and
               (pu.u.crc<>pu.checksum)
              ) then
             begin
{$ifdef DEBUG_UNIT_CRC_CHANGES}
               if (pu.u.interface_crc<>pu.interface_checksum) then
                 Comment(V_Normal,'  intfcrc change (3): '+hexstr(pu.u.interface_crc,8)+' for '+pu.u.ppufilename+' <> '+hexstr(pu.interface_checksum,8)+' in unit '+realmodulename^)
               else if (pu.u.indirect_crc<>pu.indirect_checksum) then
                 Comment(V_Normal,'  indcrc change (3): '+hexstr(pu.u.indirect_crc,8)+' for '+pu.u.ppufilename+' <> '+hexstr(pu.indirect_checksum,8)+' in unit '+realmodulename^)
               else
                 Comment(V_Normal,'  implcrc change (3): '+hexstr(pu.u.crc,8)+' for '+pu.u.ppufilename+' <> '+hexstr(pu.checksum,8)+' in unit '+realmodulename^);
{$endif DEBUG_UNIT_CRC_CHANGES}
               result:=true;
               exit;
             end;
           pu:=tused_unit(pu.next);
         end;
      end;


    procedure tppumodule.setdefgeneration;
      begin
        defsgeneration:=currentdefgeneration;
        inc(currentdefgeneration);
      end;


    procedure tppumodule.reload_flagged_units;
      var
        hp : tppumodule;
      begin
        { now reload all dependent units with outdated defs }
        hp:=tppumodule(loaded_units.first);
        while assigned(hp) do
         begin
           if hp.do_reload and
              (hp.defsgeneration<defsgeneration) then
             begin
               hp.defsgeneration:=defsgeneration;
               hp.loadppu(self)
             end
           else
             hp.do_reload:=false;
           hp:=tppumodule(hp.next);
         end;
      end;

    procedure tppumodule.end_of_parsing;
      begin
        { module is now compiled }
        state:=ms_compiled;

        { free ppu }
        discardppu;

        inherited end_of_parsing;
      end;

    procedure tppumodule.check_reload(from_module : tmodule; var do_load : boolean);

      begin
        { A force reload }
        if not do_reload then
          exit;
        Message(unit_u_forced_reload);
        do_reload:=false;
        { When the unit is already loaded or being loaded
         we can maybe skip a complete reload/recompile }
        if assigned(globalsymtable) and
          (not needrecompile) then
         begin
           { When we don't have any data stored yet there
             is nothing to resolve }
           if interface_compiled and
             { it makes no sense to re-resolve the unit if it is already finally compiled }
             not(state=ms_compiled) then
             begin
               re_resolve(from_module);
             end
           else
             Message1(unit_u_skipping_reresolving_unit,modulename^);
           do_load:=false;
         end;
      end;

    { Returns true if the module was loaded from package }
    function tppumodule.check_loadfrompackage : boolean;

      begin
        { try to load it as a package unit first }
        Result:=(packagelist.count>0) and loadfrompackage;
        if Result then
          begin
            do_reload:=false;
            state:=ms_compiled;
            { PPU is not needed anymore }
            if assigned(ppufile) then
             begin
               discardppu;
             end;
            { add the unit to the used units list of the program }
            usedunits.concat(tused_unit.create(self,true,false,nil));
          end;
      end;

      procedure tppumodule.prepare_second_load(from_module: tmodule);

      const
         CompileStates  = [ms_compile, ms_compiling_waitintf, ms_compiling_waitimpl,
                           ms_compiling_waitfinish, ms_compiling_wait, ms_compiled,
                           ms_processed];


        begin
          { try to load the unit a second time first }
          Message1(unit_u_second_load_unit,modulename^);
          Message2(unit_u_previous_state,modulename^,ModuleStateStr[state]);
          { Flag modules to reload }
          flagdependent(from_module);
          { Reset the module }
          reset(false);
          if state in CompileStates then
            begin
              Message1(unit_u_second_compile_unit,modulename^);
              state:=ms_compile;
            end
          else
            state:=ms_load;
        end;

    procedure tppumodule.try_load_ppufile(from_module : tmodule);

      begin
        Message1(unit_u_loading_unit,modulename^);
        if auPPU in search_unit_files(from_module,false) then
          state:=ms_load
        else
          state:=ms_compile;
        if not (state=ms_compile) then
         begin
           load_interface;
           setdefgeneration;
           if not (state=ms_compile) then
            begin
              load_usedunits;
              if not (state=ms_compile) then
                Message1(unit_u_finished_loading_unit,modulename^);
            end;
         end;
        { PPU is not needed anymore }
        if assigned(ppufile) then
            discardppu;
      end;

    procedure tppumodule.recompile_from_sources(from_module : tmodule);

      var
        pu : tused_unit;
      begin
        { recompile the unit or give a fatal error if sources not available }
        if not(sources_avail) then
         begin
           search_unit_files(from_module,true);
           if not(sources_avail) then
            begin
              printcomments;
              if recompile_reason=rr_noppu then
                begin
                  pu:=tused_unit(from_module.used_units.first);
                  while assigned(pu) do
                    begin
                      if pu.u=self then
                        break;
                      pu:=tused_unit(pu.next);
                    end;
                  if assigned(pu) and assigned(pu.unitsym) then
                    MessagePos2(pu.unitsym.fileinfo,unit_f_cant_find_ppu,realmodulename^,from_module.realmodulename^)
                  else
                    Message2(unit_f_cant_find_ppu,realmodulename^,from_module.realmodulename^);
                end
              else
                Message1(unit_f_cant_compile_unit,realmodulename^);
            end;
         end;
        { we found the sources, we do not need the verbose messages anymore }
        if comments <> nil then
        begin
          comments.free;
          comments:=nil;
        end;
        { Flag modules to reload }
        flagdependent(from_module);
        { Reset the module }
        reset(true);
        { mark this module for recompilation }
        if not (state in [ms_compile]) then
          state:=ms_compile;
        setdefgeneration;
      end;

    procedure tppumodule.post_load_or_compile(from_module : tmodule; second_time : boolean);

    begin
      if current_module<>self then
        internalerror(200212282);

      if in_interface then
        internalerror(200212283);

      { for a second_time recompile reload all dependent units,
        for a first time compile register the unit _once_ }
      if second_time then
        reload_flagged_units;

      { reopen the old module }
{$ifdef SHORT_ON_FILE_HANDLES}
      if from_module.is_unit and
          assigned(tppumodule(from_module).ppufile) then
         tppumodule(from_module).ppufile.tempopen;
{$endif SHORT_ON_FILE_HANDLES}
      state:=ms_processed;
    end;

    function tppumodule.loadppu(from_module : tmodule) : boolean;
      const
        ImplIntf : array[boolean] of string[15]=('implementation','interface');
      var
        do_load,
        second_time        : boolean;

      begin
        Inc(LoadCount);

        Result:=false;
        Message3(unit_u_load_unit,from_module.modulename^,
                 ImplIntf[from_module.in_interface],
                 modulename^);

        { check if the globalsymtable is already available, but
          we must reload when the do_reload flag is set }
        if (not do_reload) and
           assigned(globalsymtable) then
           exit(True);

        { reset }
        do_load:=true;
        second_time:=false;
        set_current_module(self);

        do_load:=not check_loadfrompackage;

        { A force reload }
        check_reload(from_module, do_load);

        if not do_load then
          begin
            // No need to do anything, restore situation and exit.
            set_current_module(from_module);
            exit(state=ms_compiled);
          end;

        { loading the unit for a second time? }
        if state=ms_registered then
          state:=ms_load
        else if (state in [ms_compile, ms_compiling_waitintf]) then
          begin
          { no use continuing if we must be compiled }
          // but we still need to restore current_module!
          set_current_module(from_module);
          exit(false)
          end
        else
          begin
            second_time:=true;
            prepare_second_load(from_module);
          end;

        { close old_current_ppu on system that are
          short on file handles like DOS PM }
{$ifdef SHORT_ON_FILE_HANDLES}
        if from_module.is_unit and
           assigned(tppumodule(from_module).ppufile) then
          tppumodule(from_module).ppufile.tempclose;
{$endif SHORT_ON_FILE_HANDLES}

        { try to opening ppu, skip this when we already
          know that we need to compile the unit }
        if not (state=ms_compile) then
          try_load_ppufile(from_module);

        { Do we need to recompile the unit }
        if (state=ms_compile) then
          recompile_from_sources(from_module)
        else
          state:=ms_compiled;

        Result:=(state=ms_compiled);

        // We cannot do this here, the order is all messed up...
        // if not second_time then
        //   usedunits.concat(tused_unit.create(self,true,false,nil));

        if result then
          post_load_or_compile(from_module,second_time);

        { we are back, restore current_module }
        set_current_module(from_module);
        { safety, so it does not become negative }
        if LoadCount>0 then
          Dec(LoadCount);
      end;

    procedure tppumodule.discardppu;
      begin
        { PPU is not needed anymore }
        if not assigned(ppufile) then
          exit;
        ppufile.closefile;
        ppufile.free;
        ppufile:=nil;
      end;

{*****************************************************************************
                               RegisterUnit
*****************************************************************************}


    function registerunit(callermodule:tmodule;const s : TIDString;const fn:string; out is_new:boolean) : tppumodule;


          function FindCycle(aFile, SearchFor: TModule; var Cycle: TFPList): boolean;
          // Note: when traversing, add every search file to Cycle, to avoid running in circles.
          // When a cycle is detected, clear the Cycle list and build the cycle path
          var

            aParent: tdependent_unit;
          begin
            Cycle.Add(aFile);
            aParent:=tdependent_unit(afile.dependent_units.First);
            While Assigned(aParent) do
              begin
              if aParent.in_interface then
                begin
                // writeln('Registering ',Callermodule.get_modulename,': checking cyclic dependency of ',aFile.get_modulename, ' on ',aparent.u.get_modulename);
                if aParent.u=SearchFor then
                begin
                  // unit cycle found
                  Cycle.Clear;
                  Cycle.Add(aParent.u);
                  Cycle.Add(aFile);
                  // Writeln('exit at ',aParent.u.get_modulename);
                  exit(true);
                end;
                if Cycle.IndexOf(aParent.u)<0 then
                  if FindCycle(aParent.u,SearchFor,Cycle) then
                    begin
                    // Writeln('Cycle found, exit at ',aParent.u.get_modulename);
                    Cycle.Add(aFile);
                    exit(true);
                    end;
                end;
              aParent:=tdependent_unit(aParent.Next);
              end;
           Result:=false;
          end;


      var
        ups   : TIDString;
        hp    : tppumodule;
        hp2   : tmodule;
        cycle : TFPList;
        havecycle: boolean;
{$IFDEF DEBUGCYCLE}
        cyclepath : ansistring
{$ENDIF}

      begin
        { Info }
        ups:=upper(s);
        { search all loaded units }
        hp:=tppumodule(loaded_units.first);
        hp2:=nil;
        while assigned(hp) do
         begin
           if hp.modulename^=ups then
            begin
              { only check for units. The main program is also
                as a unit in the loaded_units list. We simply need
                to ignore this entry (PFV) }
              if hp.is_unit then
               begin
                 { both units in interface ? }
                 if hp.in_interface and callermodule.in_interface then
                  begin
                    { check for a cycle }
                    Cycle:=TFPList.Create;
                    try
                      HaveCycle:=FindCycle(CallerModule,hp,Cycle);
                      if HaveCycle then
                      begin
                      {$IFDEF DEBUGCYCLE}
                         Writeln('Done cycle check');
                        CyclePath:='';
                        hp2:=TModule(Cycle[Cycle.Count-1]);
                        for i:=0 to Cycle.Count-1 do begin
                          if i>0 then CyclePath:=CyclePath+',';
                          CyclePath:=CyclePath+TModule(Cycle[i]).realmodulename^;
                        end;
                        Writeln('Unit cycle detected: ',CyclePath);
                        {$ENDIF}
                        Message2(unit_f_circular_unit_reference,callermodule.realmodulename^,hp.realmodulename^);
                      end;
                    finally
                      Cycle.Free;
                    end;
                    if assigned(hp2) then
                      Message2(unit_f_circular_unit_reference,callermodule.realmodulename^,hp.realmodulename^);
                  end;
                 break;
               end;
            end;
           { the next unit }
           hp:=tppumodule(hp.next);
         end;
        { the unit is not in the loaded units,
          we create an entry and register the unit }
        is_new:=not assigned(hp);
        if is_new then
         begin
           Message1(unit_u_registering_new_unit,ups);
           hp:=tppumodule.create(callermodule,s,fn,true);
           addloadedunit(hp);
         end;
        { return }
        registerunit:=hp;
      end;

end.