amicommon: implement StackTop for other Amiga-like systems

git-svn-id: trunk@36697 -

rtl/amicommon/sysos.inc

@@ -44,6 +44,13 @@
                     System Dependent Structures/Consts
 *****************************************************************************}
 
+{$ifndef FPC_SYSTEM_HAS_STACKTOP}
+{$define FPC_SYSTEM_HAS_STACKTOP}
+function StackTop: pointer;
+begin
+  StackTop:=FindTask(nil)^.tc_SPUpper;
+end;
+{$endif FPC_SYSTEM_HAS_STACKTOP}
 
 const
   CTRL_C           = 20;      { Error code on CTRL-C press }

rtl/amiga/system.pp

@@ -302,7 +302,7 @@ end;
 begin
   IsConsole := TRUE;
   StackLength := CheckInitialStkLen(InitialStkLen);
-  StackBottom := Sptr - StackLength;
+  StackBottom := StackTop - StackLength;
 { OS specific startup }
   AOS_wbMsg:=nil;
   ASYS_origDir:=0;