On 05/09/2019 15.45, Segher Boessenkool wrote: > Hi Rasmus, > > On Thu, Sep 05, 2019 at 01:07:11PM +0200, Rasmus Villemoes wrote: >> On 05/09/2019 02.18, Nick Desaulniers wrote: >>> Is it too late to ask for a feature test macro? Maybe one already >>> exists? >> >> No, not as far as I know. > > [ That's not what a feature test macro is; a feature test macro allows the > user to select some optional behaviour. Things like _GNU_SOURCE. ] > >> Perhaps something like below, though that >> won't affect the already released gcc 9.1 and 9.2, of course. > > That is one reason to not want such a predefined macro. Another reason > is that you usually need to compile some test programs *anyway*, to see if > some bug is present for example, or to see if the exact implementation of > the feature is beneficial (or harmful) to your program in some way.
OK, I think I'll just use a version check for now, and then switch to a Kconfig test if and when clang grows support. >> gcc maintainers, WDYT? Can we add a feature test macro for asm inline()? > > > Why would GCC want to have macros for all features it has? Well, gcc has implemented __has_attribute() which is similar - one could detect support by compiling a trivial test program. Or the same could be said for many of the predefined macros that are conditionally defined, e.g. __HAVE_SPECULATION_SAFE_VALUE. But I was just throwing the question into the air, I won't pursue this further. Thanks, Rasmus
