Re: Implicition declarations of functions and bugs
On 3/11/06, Goswin von Brederlow <brederlo@informatik.uni-tuebingen.de> wrote:
> > $ gcc-3.3 -c -g -O -Wall t.c
> > t.c: In function `foo':
> > t.c:4: warning: implicit declaration of function `strdup'
> > t.c:4: warning: return makes pointer from integer without a cast
>
> (all asm is from amd64)
>
> 0000000000400500 <foo>:
> 400500: 48 83 ec 08 sub $0x8,%rsp
> 400504: 31 c0 xor %eax,%eax
> 400506: e8 d5 fe ff ff callq 4003e0 <strdup@plt>
> 40050b: 48 83 c4 08 add $0x8,%rsp
> 40050f: 48 98 cltq
> 400511: c3 retq
>
> The return value of strdup is passed back unaltered. No crash.
The context of this discussion was ia64, but I realize now that this
probably wasn't obvious for debian-devel subscribers. I should have
been clear about that. In any case, ia64 calling convention say that
a 32-bit integer value in a (64-bit) register may contain garbage in
the top 32 bits, hence the result from a function returning "int" will
be sign- or zero-extended when converted to a 64-bit value, hence the
crash.
--david
--
Mosberger Consulting LLC, http://www.mosberger-consulting.com/
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