Subj : BC++ 5.02 Stack Restore Bug
To   : borland.public.cpp.borlandcpp
From : kurt jensen
Date : Tue Nov 30 2004 04:41 pm

for some perverse reason my Borland C++ 5.02 compiler has decided to
pull funny tricks on me.  after spending a week blaming the DLL vendor I
stumbled onto a "situation" in the assembly representation of my
compiled code.  

everything looks fine until you get to the "ret" statement - then we
ALWAYS return to address 0x00000000.  the reason is that the compiler
left out one very important statement, "mov esp,ebp", i.e.  the stack
pointer is NEVER restored before popping ebp and 'ret'urning from the
function call.  because of that, we always try to return to the wrong
address which is always 0 because of a parameter in a function call.

anybody seen this particular problem before???  anybody have any idea
what would possess the compiler to pull such a stunt???  and, more
importantly, how can I convince it to properly restore the stack before
returning???

TIA,

Kurt


below is the "C++ to Assembler" representation of the problem.  notice
at the end after label @156, we properly pop ebx, "mov esp,ebp" is
missing, pop ebp, and 'ret'urn.


@TSCOR20CaptureThread@IncrCaptureOk$qi	proc	near
?live1@3616:
   ;	
   ;	bool TSCOR20CaptureThread::IncrCaptureOk(int buffer)
   ;	
	?debug L 779
	push      ebp
	mov       ebp,esp
	push      ebx
	mov       eax,dword ptr [ebp+12]
	mov       ebx,dword ptr [ebp+8]
   ;	
   ;	{
   ;		FlyCaptureError CameraError;
   ;	
   ;		if (buffer > 0)
   ;	
	?debug L 783
?live1@3632: ; EBX = this, EAX = buffer
@152:
	test      eax,eax
	jle       short @153
   ;	
   ;		{
   ;			CameraError = flycaptureUnlock(FCameraContext, buffer-1);
   ;	
	?debug L 785
	dec       eax
	push      eax
	push      dword ptr [ebx+22]
	call      flycaptureUnlock
   ;	
   ;			if (CameraError == FLYCAPTURE_OK)
   ;	
	?debug L 786
?live1@3664: ; EBX = this, EAX = CameraError
	test      eax,eax
	jne       short @155
   ;	
   ;				CaptureOK++;
   ;	
	?debug L 787
?live1@3680: ; EBX = this
	inc       dword ptr [ebx+30]
   ;	
   ;		}	//	then, started
   ;	
	?debug L 788
?live1@3696: ; 
	jmp       short @155
   ;	
   ;		else
   ;		{
   ;			CaptureOK++;
   ;	
	?debug L 791
?live1@3712: ; EBX = this
@153:
	inc       dword ptr [ebx+30]
   ;	
   ;		}	//	else
   ;	
   ;		return true;
   ;	
	?debug L 794
?live1@3728: ; 
@155:
	mov       al,1
   ;	
   ;	}	//	TSCOR20CaptureThread::IncrCaptureOk()
   ;	
	?debug L 795
@157:
@156:
	pop       ebx
	pop       ebp
	ret 
	?debug L 0
@TSCOR20CaptureThread@IncrCaptureOk$qi	endp

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