Martin Sebor <msebor@xxxxxxxxx> writes:
>>> If I understand correctly it sounds to me like what you're looking
>>> for is the opposite of what I requested in bug 59219 in a slightly
>>> different context. By defining a function like memcpy inline and
>>> in terms of __builtin__memcpy_chk GCC expands it inline when it
>>> can even when -fno-builtin is used. The bug suggests to change
>>> it but since it's not been implemented (yet) and may never be it
>>> should be possible to rely on the current behavior.
>>
>> Dunno if it's opposite or not as I don't quite understand you case. Most
>> probably it's ortogonal to what I need.
>>
>> I need to be able to port particular code that works with -std=gnu89
>> compilation mode to -std=gnu99 or -std=gnu11. This code uses its own
>> implementation of libc/libm that heavily uses "extern inline" for
>> standard functions. Right now this task seems to be close to
>> imopossible, as GCC builtins are always (implicitly) declared as if
>> -std=gnu89 mode were active. I.e., builtins seem to implicitly get
>> "extern inline" declaration, while in -std=gnu99 and above modes they
>> rather should be declared "inline".
>
> I was suggesting a workaround until gcc is fixed, one that should
> let you benefit from the gcc intrinsics while using -fno-builtin
> or -ffreestanding.
>
> For example, defining memcpy like this in a header:
>
> inline __attribute__ ((always_inline, artificial)) void*
> memcpy (void* restrict d, const void* restrict s, size_t n) {
> return __builtin___memcpy_chk (d, s, n, __builtin_object_size
> (d, 1));
> }
>
> makes it possible to include it in more than one translation unit
> in the same program compiled with either of the two options and
> benefit from the builtins. The program will also benefit from
> the buffer overflow checking done by GCC. What you will need to
> do in your libc is define __memcpy_chk and handle the runtime
> buffere overflow detection when you can before forwarding the
> call to your own memcpy.
Ah, well, I now see your point. It's interesting and it'd probably
help, but it seems I've found perfect workaround:
extern inline __attribute__ ((gnu_inline))
int abs(int i) { return (i >= 0) ? i : -i; }
should do the trick, I think.
Description of 'gnu_inline' happens to be right above 'artificial' in GCC
info manual, and it is when I was looking for the latter I've noticed the
former, so you did help a lot, thanks!
-- Sergey.
