Hi,
I am trying to compile and run some parts of Lazarus
(lcl\interfaces\win32) with -Criot. I get some overflow errors I don't
understand. I tried to understand the logic behind the generated
assembler and made a small test program, which doesn't give an overflow
error, but that has the same (AFAICS) wrong assembler. I am using fpc 2.3.1.
Pascal code:
program Project1;
{$mode objfpc}{$H+}
const
WAIT_OBJECT_0 = 0;
var
retVal : dword;
FWaitHandleCount: dword;
begin
retVal := 258;
FWaitHandleCount := 0;
if retVal = WAIT_OBJECT_0 + FWaitHandleCount then
writeln('OK');
readln;
end.
Generated assembler:
.Ll3:
# [14] FWaitHandleCount := 0;
movl $0,U_P$PROJECT1_FWAITHANDLECOUNT
.stabn 68,0,15,.Ll4 - _main
.Ll4:
# [15] if retVal = WAIT_OBJECT_0 + FWaitHandleCount then
movl U_P$PROJECT1_FWAITHANDLECOUNT,%eax
jnb .Lj9
call FPC_OVERFLOW
.Lj9:
cmpl U_P$PROJECT1_RETVAL,%eax
je .Lj7
jmp .Lj8
Why is there an overflow check ?
What can set the carry flag used by the jnb?
If I change
if retVal = WAIT_OBJECT_0 + FWaitHandleCount then
to
if retVal = FWaitHandleCount then
then there is no overflow check.
Vincent
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