Re: [PATCH 0/2] Work around broken clang. Again.

On Mon, Mar 20, 2023 at 03:17:24PM +0100, Michal Prívozník wrote: > On 3/16/23 15:51, Andrea Bolognani wrote: >> On Wed, Mar 15, 2023 at 08:10:26PM +0100, Michal Privoznik wrote: >>> We ran into so many clang bugs recently, that I'm strongly in favor of >>> making it optional and aim on gcc only. Debugging these issues burns our >>> time needlessly. >>> >> [...] >>> >>> After these patches, there is still one qemuxml2argvtest case failing, >>> and it's simply because no matter how hard I try, I can't stop clang >>> from optimizing the function. >>> >> [...] >>> >>> At this point, I think we can call clang broken and focus our time on >>> developing libvirt. Not coming up with hacks around broken compilers. >> >> clang is the default compiler for FreeBSD and macOS, both of which >> are officially supported platforms. Unless we are willing to change >> that, ignoring clang is simply out of the question. > > I'm fine with doing that change. FreeBSD offers option to install gcc. > And for macOS - the fact we compile there says absolutely nothing. > Anybody willing to make libvirt work on macOS is more than welcome to > post patches. clang is the system compiler for those platforms, and IMHO we should be compatible with it. Just as Fedora was long unhappy with certain apps trying to force use of clang, when Fedora's system compiler was GCC, the opposite is reasonable for other platforms. >> A thought about VIR_OPTNONE. It seems to me that we'd want to apply >> this to all the functions that currently are marked with G_NO_INLINE >> for mocking purposes. So, wouldn't it make sense to instead have a >> single VIR_MOCKABLE annotation that combines the two, and use that >> everywhere? >> > > The problem is, __attribute__((optnone)) works only when passed at > function definition, while noinline can be passed at function > definition. Is that a problem in fact ? We only need to suppress inlining when the calling function is in the same compilation unit as the called function. Likewise for this return value optimization. So if 'noinline' annotation was in the definition, rather than the declaration, it would be fine for our purposes. I think it would make sense to have a VIR_MOCKABLE annotation that covered 'noline', 'optnone' and 'noipa' attributes (the precise set varying according to what compiler we target). If anything this is more appealing that having it in the .h file, since this annotations are not intended to influence callers from external compilation units. We would need to update our test program that validates the existance of noinline for mocked functions to look in the .c instead of .h