svn commit: r285284 - head/lib/liblzma

[NGie Cooper]

On Wed, Jul 8, 2015 at 3:18 PM, Dimitry Andric <dim at freebsd.org> wrote:
> Check whether the path starts with /usr/bin, maybe?  Normally, you would
> check for the existence of a random header in a configure script.  But
> from within a C source file, it's not that easy.
>
> That said, immintrin.h is available for all usable versions of clang,
> and should be available in all versions of gcc >= 4.4 (at least, if I
> read gcc's commit history correctly).  And gcc in base is definitely not
> 4.4. :-)

$ cat ~/has_immintrin.c
#include <sys/cdefs.h>

#if __has_include(<immintrin.h>)
#error "I have immintrin.h"
#else
#error "I don't have immintrin.h"
#endif
$ clang -c ~/has_immintrin.c
/home/ngie/has_immintrin.c:4:2: error: "I have immintrin.h"
#error "I have immintrin.h"
 ^
1 error generated.
$ gcc -c ~/has_immintrin.c
/home/ngie/has_immintrin.c:6:2: error: #error "I don't have immintrin.h"

Sadly this macro wasn't added until gcc 5.x:
https://gcc.gnu.org/gcc-5/changes.html

Cheers,
-NGie