Re: [Qemu-devel] [PATCH for-4.0 1/7] configure: Add a test for the minimum compiler version

[Peter Maydell]

On Mon, 3 Dec 2018 at 14:16, Daniel P. Berrangé <address@hidden> wrote:
> NB although this will succeed, it is not technically checking the
> right thing on macOS platforms as their clang used a completely
> different numbering scheme. It just happens to have larger numbers
> than upstream clang, so we'll always succeed.
>
> Compare clang on Ubuntu:
>
>   https://travis-ci.org/qemu/qemu/jobs/460892603
>
>   $ clang --version
>   clang version 5.0.0 (tags/RELEASE_500/final)
>
> with clang on macOS:
>
>   https://travis-ci.org/qemu/qemu/jobs/460892611
>
>   $ clang --version
>   Apple LLVM version 9.1.0 (clang-902.0.39.2)
>
> Fortunately there's a mapping recorded here:
>
>    https://en.wikipedia.org/wiki/Xcode#Latest_versions
>
> See "LLVM" and "CLang version string" columns.

...but overall it is better to check for feature presence/absence
where possible rather than using a version number check.
clang does at least make this easier than it has historically
been for gcc.

thanks
-- PMM