RE: Possible bug with __attribute__((alias)) in gcc-3.3

[Danny Smith <danny_r_smith_2001 at yahoo dot co dot nz>]

Nicholas wrote:

> Hi All,
> 
> Gerrit and I were discussing this off-list, but I thought it appropriate
> that I move it to the main list since he has confirmed the problem.
> 
> Here's the problem, programs are segfaulting when the are linked to a
> symbol which was aliased using __attribute__((alias)) in a dll. Here is
> a small testcase:
> 
> 
> foo.c:
> #include <stdio.h>
> 
> int __foo (void) {
>    printf("foo\r\n");
>    return 0;
> }
> int __attribute__ ((alias("__foo"))) foo (void);
> 

One problem is that you (or gcc) need to tell ld that 'foo' is function, not
data.

Adding this to file foo.c (after the alias declaration):
__asm__ (".def _foo; .scl 2; .type 32; .endef\n");
would do that.

That fixes the testcase on mingw anyway. 

I'm testing a patch now that would make gcc do that too (for aliased 
functions).

However, in general,when you do dllexport with code written in straight
assembler, you will need to add a function directive like the one above
so that the linker does the right thing. 

(BTW, you've just reminded me of a  similar problem in libffi assembly code
that needs to be fixed.  Thanks )

Or...
The usual windows way would be to put your aliasing for dllexports in a def
file.

Danny


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