On 12/9/22 12:52, Peter Maydell wrote:
The new code makes it much harder to move our compiler version
requirements forward in future, because there's no longer a simple
"check for normal clang X or apple clang Y" test where we can
bump up X and Y based on what's provided in the various host
platforms we have to support. Doesn't meson provide a way to do
the version check on the version number the way we were doing
previously?
Yes, I could just do the check with #error just like before.
For GCC I used the nicer "compiler.version().version_compare('>=x.y')"
check. For clang we have to deal with both upstream and Apple version
numbers; it's also possible to check for __apple_build_version__ to
distinguish between the two and then do version_compare(), but at that
point it's easier to just use cc.compiles() and #error.
While it's possible to learn the upstream version corresponding to Apple
compilers with "c++ --verbose", it is not really machine-friendly so
Meson does not attempt to parse it and neither did QEMU's configure script.
So I went for the trick of using -Wpragma-pack, which was extracted from
https://github.com/simd-everywhere/simde/blob/master/simde/simde-detect-clang.h.
The advantage is that you only have one check, the disadvantage is of
course that it obscures what's going on. I can add a clearer comment
around the check, or switch to #error and add a pointer to
https://trac.macports.org/wiki/XcodeVersionInfo where the mapping can be
found, or really anything else that is your preference.
Paolo
