diff --git a/rtl/inc/lineinfo.pp b/rtl/inc/lineinfo.pp
index 2571ad9ace..51de4a13d2 100644
--- a/rtl/inc/lineinfo.pp
+++ b/rtl/inc/lineinfo.pp
@@ -29,7 +29,7 @@ type
 {$ENDIF}
 
 function GetLineInfo(addr:ptruint;var func,source:string;var line:longint) : boolean;
-function StabBackTraceStr(addr:CodePointer):string;
+function StabBackTraceStr(addr:CodePointer):shortstring;
 procedure CloseStabs;
 
 var
@@ -277,7 +277,7 @@ begin
      seek(e.f,stabstrofs+dirstab.strpos);
      blockread(e.f,source[1],high(source)-1,res);
      dirlength:=strlen(@source[1]);
-     source[0]:=chr(dirlength);
+     SetLength(source,dirlength);
    end
   else
    dirlength:=0;
@@ -285,13 +285,13 @@ begin
    begin
      seek(e.f,stabstrofs+filestab.strpos);
      blockread(e.f,source[dirlength+1],high(source)-(dirlength+1),res);
-     source[0]:=chr(strlen(@source[1]));
+     SetLength(source,strlen(@source[1]));
    end;
   if funcstab.ntype<>0 then
    begin
      seek(e.f,stabstrofs+funcstab.strpos);
      blockread(e.f,func[1],high(func)-1,res);
-     func[0]:=chr(strlen(@func[1]));
+     SetLength(func,strlen(@func[1]));
      i:=pos(':',func);
      if i>0 then
       Delete(func,i,255);
@@ -304,7 +304,7 @@ begin
 end;
 
 
-function StabBackTraceStr(addr:CodePointer):string;
+function StabBackTraceStr(addr:CodePointer):shortstring;
 var
   func,
   source : string;
diff --git a/rtl/inc/lnfodwrf.pp b/rtl/inc/lnfodwrf.pp
index d096c4e6e6..6482e4409b 100644
--- a/rtl/inc/lnfodwrf.pp
+++ b/rtl/inc/lnfodwrf.pp
@@ -32,7 +32,7 @@ type
 {$ENDIF}
 
 function GetLineInfo(addr:codeptruint;var func,source:string;var line:longint) : boolean;
-function DwarfBackTraceStr(addr: CodePointer): string;
+function DwarfBackTraceStr(addr: CodePointer): shortstring;
 procedure CloseDwarf;
 
 var
@@ -1415,7 +1415,7 @@ begin
 end;
 
 
-function DwarfBackTraceStr(addr: CodePointer): string;
+function DwarfBackTraceStr(addr: CodePointer): shortstring;
 var
   func,
   source : string;
diff --git a/rtl/unix/dos.pp b/rtl/unix/dos.pp
index e75d87ab56..dd9cfbf7f2 100644
--- a/rtl/unix/dos.pp
+++ b/rtl/unix/dos.pp
@@ -685,7 +685,7 @@ End;
                                --- File ---
 ******************************************************************************}
 
-Function FSearch(path : pathstr;dirlist : string) : pathstr;
+Function FSearch(path : pathstr;dirlist : shortstring) : pathstr;
 Var
   info : BaseUnix.stat;
 Begin
@@ -806,7 +806,7 @@ Begin
 End;
 
 
-Function EnvStr (Index: longint): String;
+Function EnvStr (Index: longint): ShortString;
 Var
   i : longint;
   p : PPAnsiChar;
@@ -830,7 +830,7 @@ Begin
 end;
 
 
-Function GetEnv(EnvVar: String): String;
+Function GetEnv(EnvVar: ShortString): ShortString;
 var
   p     : PAnsiChar;
 Begin
diff --git a/rtl/unix/timezone.inc b/rtl/unix/timezone.inc
index 0b69d678c8..d2831b07e0 100644
--- a/rtl/unix/timezone.inc
+++ b/rtl/unix/timezone.inc
@@ -252,7 +252,7 @@ begin
     TimeZoneDir:=TimeZoneDir+'/';
 end;
 
-function ReadTimezoneFile(fn:shortstring) : Boolean;
+function ReadTimezoneFile(fn:string) : Boolean;
 
   function decode(const l:longint):longint;
   begin
@@ -489,7 +489,7 @@ Const
 
 {$ifndef FPC_HAS_GETTIMEZONEFILE}
 
-function GetTimezoneFile:shortstring;
+function GetTimezoneFile:string;
 var
   f,len : longint;
   fn,s : shortstring;