On Tue, 24 Jul 2007, Al Viro wrote:
> AFAICS, the patch below should do it for i386; instead of
> using a dummy loop to tell gcc that this sucker never returns,
> we do
> static void __always_inline __noreturn __BUG(const char *file, int line);
> containing the actual asm we want to insert and define BUG() as
> __BUG(__FILE__, __LINE__). It looks safe, but I don't claim enough
> experience with gcc __asm__ potential nastiness, so...
Sounds like it doesn't work:
http://gcc.gnu.org/ml/gcc/2007-02/msg00107.html
[The] programmer won't get optimization he wants as after inlining this as
after inlining this attribute information becomes completely lost.
What about __builtin_trap?
It results in int 6 that might not be applicable, but adding some control
over it to i386 backend is definitly an option.
Honza
It seems like if __BUG() is not inlined, you get the bogus noreturn does
return warning. If it is inlined, then you lose the noreturn attribute and
un-reachable code paths aren't eliminated. Adding __builtin_trap after the
asm might be an ok fix. It will emit a spurious int 6, but that won't even be
reached since the asm doesn't return, and it probably be less extra code than
the loop.
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