On 02/12/2010 00:12, Cary Coutant wrote:
> Think about it -- any failure to bind to an interposed copy of memcpy
> (or any other library call generated by gcc) is indistinguishable from
> the compiler choosing to generate the code inline.
Indeed, replacing library functions is a tricky business in the presence of
optimisations:
> $ cat main.c
> #include <stdio.h>
>
> int main (int argc, const char **argv)
> {
> printf ("hello world\n");
> return 0;
> }
>
> $ cat myprintf.c
> #include <stdlib.h>
>
> int printf (const char *fmt, ...)
> {
> abort ();
> }
>
> $ gcc -O3 main.c myprintf.c -o test1
>
> $ ./test1.exe
> hello world
>
> $ cat main2.c
> #include <stdio.h>
>
> int main (int argc, const char **argv)
> {
> printf ("<%s>", "hello world\n");
> return 0;
> }
>
> $ gcc -O3 main2.c myprintf.c -o test2
>
> $ ./test2.exe
> Aborted (core dumped)
>
> $
I think the answer to this is that you have to use -fno-builtin if you want
to interpose a library function, regardless of LTO or not.
cheers,
DaveK
