9.3 to 10.2 migration, determining if clang is used

Brooks Davis brooks at freebsd.org
Tue Oct 13 21:31:49 UTC 2015

On Tue, Oct 13, 2015 at 11:13:11AM -0700, Patrick Powell wrote:
> I just started doing a 9.3 to 10.2 migration of a bunch of applications 
> and discovered that some of the options used
> to generate the applications were slightly different.   I just know that 
> this has been covered before,  but I could not
> find a definitive method or set of methods to use to determine if the 
> old GCC compiler or the new CLANG compiler
> is being used.   Could the ports wizards (and/or autoconf experts) help 
> me a bit?
> (Aside:  the clang compiler diagnostics and warnings are very thorough 
> and quite clear.  Nicely done, especially
> the addition of the information about the flag to turn this warning 
> off.  I also like the pragmas to
> control warnings and the push/pop pragma facility.  This may have been 
> in the GCC compiler but I missed it.)
> 1. If the application is to be generated via the PORT infrastructure,  
> what do you
>      put in the port Makefile to determine if CLANG (10.2) or GCC (9.3) 
> is being used?
>     Something like below.  Note: the examples below are a bit contrived, 
> but the idea is to set
>     some MAKE variable to different values depending on CLANG or GCC in use.
>     .if defined(CC_IS_CLANG)
>     MYFLAGS+= -Wall -Werror -Wno-error=unused
>     .else
>     .if defined(CC_IS_GCC)
>     MYFLAGS+= -Wall -Werror -Wno-unused
>     .endif
>     .endif

For ports, I think you are looking for USES=compiler:features (see
ports/Mk/Uses/compiler.mk).  I don't know the answer for autoconf.

-- Brooks
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