On Tue, 13 Jul 2021, LIU Hao wrote:
在 7/13/21 5:02 PM, Jonathan Marler 写道:
Thanks for the convenient info. However, when I try to use
__attribute__((__weak__)) I get a compiler warning from GCC, i.e.
extern __inline__ __attribute__((__weak__))
void foo(void) {}
int main(int argc, char *argv[])
{
foo();
}
$ gcc main.c
main.c:2:10: warning: inline function ‘foo’ declared weak [-Wattributes]
2 | void foo(void) {}
| ^~~
I'm having a hard time figuring out why I get this warning. The info you
sent looks consistent with the docs I'm finding, but this warning makes it
look like GCC thinks the "weak" attribute is redundant? Note that I still
get this same warning if I remove the "extern", so it seems like GCC
doesn't like inline and the weak attribute...any idea why?
(Please *Reply to All*.)
There must have been reasons why GCC ignores `weak` attribute on inline
functions [1]. It might be technical limitation, but I think it makes no
sense, because 1) Clang accepts, and 2) decomposing the two attributes
actually works as expected [2].
Overall I'd suggest to avoid using `weak` if it's possible; it's kinda
tricky/messy on COFF targets, and IIRC there's a number of cases with
GCC/binutils where it doesn't quite work as you'd want to. (On ELF it's
robust though.)
Do things work out if you use the existing __mingw_ovr attribute define?
That one iirc expands to something which is always inlined and doesn't
expect any global definition.
// Martin
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