* Since StackTop=StackBottom+StackLength, any two variables are sufficient to describe stack, the third one is redundant.

* As a first part of cleanup, replaced StackTop with function returning StackBottom+StackLength.
* On Win32 and Win64, StackTop returns the stack base from TIB instead.

git-svn-id: trunk@27119 -

rtl/emx/system.pas

@@ -535,7 +535,7 @@ begin
             begin
                 stackbottom:=pointer(heap_brk);     {In DOS mode, heap_brk is
                                                      also the stack bottom.}
-                StackTop := StackBottom + InitialStkLen;
+                StackLength:=sptr-stackbottom;
 {$WARNING To be checked/corrected!}
                 ApplicationType := 1;   (* Running under DOS. *)
                 IsConsole := true;
@@ -549,8 +549,11 @@ begin
         osOS2:
             begin
                 DosGetInfoBlocks (@TIB, @PIB);
-                StackBottom := pointer (TIB^.Stack);
-                StackTop := TIB^.StackLimit;
+                StackLength:=CheckInitialStkLen(InitialStklen);
+                { TODO: verify if TIB^.StackLimit is correct,
+                  from MSWindows point of view TIB^.Stack should be used instead }
+                StackBottom := TIB^.StackLimit - StackLength;
+
                 Environment := pointer (PIB^.Env);
                 ApplicationType := PIB^.ProcType;
                 ProcessID := PIB^.PID;
@@ -562,7 +565,7 @@ begin
             begin
                 stackbottom:=nil;   {Not sure how to get it, but seems to be
                                      always zero.}
-                StackTop := StackBottom + InitialStkLen;
+                StackLength:=sptr-stackbottom;
 {$WARNING To be checked/corrected!}
                 ApplicationType := 1;   (* Running under DOS. *)
                 IsConsole := true;
@@ -570,7 +573,6 @@ begin
             end;
     end;
     exitproc:=nil;
-    StackLength := CheckInitialStkLen (InitialStkLen);
 
     {Initialize the heap.}
     initheap;

rtl/gba/system.pp

@@ -177,7 +177,7 @@ end;
 
 begin
   StackLength := CheckInitialStkLen(InitialStkLen);
-  StackBottom := StackTop - StackLength;
+  StackBottom := Sptr - StackLength;
 { OS specific startup }
 
 { Setup heap }

rtl/go32v2/system.pp

@@ -647,7 +647,6 @@ Begin
   and to ensure that StackLength = StackTop - StackBottom }
   StackLength := CheckInitialStkLen(InitialStkLen)-256;
   StackBottom := __stkbottom;
-  StackTop := StackBottom + StackLength;
   { To be set if this is a GUI or console application }
   IsConsole := TRUE;
   { To be set if this is a library and not a program  }

rtl/inc/system.inc

@@ -682,6 +682,13 @@ End;
                              Miscellaneous
 *****************************************************************************}
 
+{$ifndef FPC_SYSTEM_HAS_STACKTOP}
+function StackTop: pointer;
+begin
+  result:=StackBottom+StackLength;
+end;
+{$endif FPC_SYSTEM_HAS_STACKTOP}
+
 {$ifndef FPC_SYSTEM_HAS_GET_PC_ADDR}
   { This provides a dummy implementation
     of get_pc_addr function, for CPU's that don't need

rtl/inc/systemh.inc

@@ -701,10 +701,10 @@ Var
   StdErr      : Text;
   InOutRes    : Word;
   { Stack checking }
-  StackTop,
   StackBottom : Pointer;
   StackLength : SizeUInt;
 
+function StackTop: Pointer;
 
 { Numbers for routines that have compiler magic }
 {$I innr.inc}

rtl/linux/system.pp

@@ -351,9 +351,8 @@ begin
 {$endif}
 {$endif}
   IsConsole := TRUE;
-  StackTop := initialstkptr;
   StackLength := CheckInitialStkLen(initialStkLen);
-  StackBottom := StackTop - StackLength;
+  StackBottom := initialstkptr - StackLength;
   { Set up signals handlers (may be needed by init code to test cpu features) }
   InstallSignals;
 {$if defined(cpui386) or defined(cpuarm)}

rtl/msdos/system.pp

@@ -340,7 +340,6 @@ begin
 end;
 
 begin
-  StackTop := __stktop;
   StackBottom := __stkbottom;
   StackLength := __stktop - __stkbottom;
   InstallInterruptHandlers;

rtl/nds/system.pp

@@ -272,7 +272,7 @@ end;
 
 begin
   StackLength := CheckInitialStkLen(InitialStkLen);
-  StackBottom := StackTop - StackLength;
+  StackBottom := Sptr - StackLength;
 { OS specific startup }
 
 { Set up signals handlers }

rtl/os2/system.pas

@@ -1125,11 +1125,10 @@ begin
     end;
 {$ENDIF OS2EXCEPTIONS}
     DosGetInfoBlocks (@TIB, @PIB);
-    StackBottom := TIB^.Stack;
-{ $IFNDEF OS2EXCEPTIONS}
-    StackTop := TIB^.StackLimit;
-{ $ENDIF OS2EXCEPTIONS}
     StackLength := CheckInitialStkLen (InitialStkLen);
+    { TODO: verify if TIB^.StackLimit is correct,
+      from MSWindows point of view TIB^.Stack should be used instead }
+    StackBottom := TIB^.StackLimit - StackLength;
 
     {Set type of application}
     ApplicationType := PIB^.ProcType;

rtl/wii/system.pp

@@ -247,7 +247,7 @@ end;
 
 begin
   StackLength := CheckInitialStkLen(InitialStkLen);
-  StackBottom := StackTop - StackLength;
+  StackBottom := Sptr - StackLength;
 { OS specific startup }
 
 { Set up signals handlers }

rtl/win32/system.pp

@@ -128,6 +128,12 @@ function main_wrapper(arg: Pointer; proc: Pointer): ptrint; forward;
 procedure OutermostHandler; external name '__FPC_DEFAULT_HANDLER';
 {$endif FPC_USE_WIN32_SEH}
 
+{$define FPC_SYSTEM_HAS_STACKTOP}
+function StackTop: pointer; assembler;nostackframe;
+asm
+   movl  %fs:(4),%eax
+end;
+
 { include system independent routines }
 {$I system.inc}
 
@@ -642,9 +648,6 @@ function CheckInitialStkLen(stklen : SizeUInt) : SizeUInt;
     result:=tpeheader((pointer(getmodulehandle(nil))+(tdosheader(pointer(getmodulehandle(nil))^).e_lfanew))^).SizeOfStackReserve;
   end;
 
-var
-  st : Pointer;
-
 begin
   { get some helpful informations }
   GetStartupInfo(@startupinfo);
@@ -654,12 +657,6 @@ begin
 
   MainInstance:=SysInstance;
 
-  asm
-    movl %fs:(4),%eax
-    movl %eax,st
-  end;
-  StackTop:=st;
-
   { pass dummy value }
   StackLength := CheckInitialStkLen($1000000);
   StackBottom := StackTop - StackLength;

rtl/win64/system.pp

@@ -116,6 +116,12 @@ asm
 end;
 {$endif FPC_USE_WIN64_SEH}
 
+{$define FPC_SYSTEM_HAS_STACKTOP}
+function StackTop: pointer; assembler;nostackframe;
+asm
+   movq  %gs:(8),%rax
+end;
+
 { include system independent routines }
 {$I system.inc}
 
@@ -581,14 +587,7 @@ function CheckInitialStkLen(stklen : SizeUInt) : SizeUInt;
     result:=tpeheader((pointer(getmodulehandle(nil))+(tdosheader(pointer(getmodulehandle(nil))^).e_lfanew))^).SizeOfStackReserve;
   end;
 
-
-function GetExceptionPointer : Pointer; assembler;nostackframe;
-asm
-  movq %gs:(8),%rax
-end;
-
 begin
-  StackTop:=GetExceptionPointer;
   { pass dummy value }
   StackLength := CheckInitialStkLen($1000000);
   StackBottom := StackTop - StackLength;

rtl/wince/system.pp

@@ -1350,15 +1350,9 @@ end;
 {$endif WINCE_EXCEPTION_HANDLING}
 
 procedure Exe_entry;[public, alias : '_FPC_EXE_Entry'];
-var
-  st: pointer;
 begin
   IsLibrary:=false;
 {$ifdef CPUARM}
-  asm
-    str sp,st
-  end;
-  StackTop:=st;
   asm
     mov fp,#0
     bl PASCALMAIN;
@@ -1373,11 +1367,6 @@ begin
     mov %esp,%fs:(0)
   {$endif WINCE_EXCEPTION_HANDLING}
     pushl %ebp
-    movl %esp,%eax
-    movl %eax,st
-  end;
-  StackTop:=st;
-  asm
     xorl %eax,%eax
     movw %ss,%ax
     movl %eax,_SS
@@ -1758,7 +1747,7 @@ initialization
   if not(IsLibrary) then
     SysInitFPU;
   StackLength := CheckInitialStkLen(InitialStkLen);
-  StackBottom := StackTop - StackLength;
+  StackBottom := Sptr - StackLength;
   { some misc stuff }
   hprevinst:=0;
   if not IsLibrary then