Improvement for bug #78360 - also try host name

[smalyshev]

This way if a compiler produces broken machine name, we can always
override with --host.

[nikic]

I don't think this really addresses the root issue. The problem is that we're trying to look for gmp.h in a specific location, even though gmp.h is already on the default include path. We should instead be checking whether the compiler sees the gmp.h header, e.g. by using AC_LINK_IFELSE.

[cmb69]

Since we're using pkg-config for several other extensions as well, shouldn't we use it for ext/gmp too?

[nikic]

GMP does not support pkg-config, unfortunately.

[smalyshev]

I agree that it is better to let the compiler figure out if it can see the header. My autoconf-fu just wasn't strong enough to figure out how to do that right, but I'll take another look. Shouldn't it be AC_COMPILE_IFELSE though? If we're looking for header, linking is not necessary I think?

[nikic]

Maybe @petk also has ideas here on how to do this nicely.

[petk]

Yes, the -print-multiarch seems to be the name of this directory, yes. How about then another sed? Unless this unknown is also output by PHP's scripts then the $host_vendor might be unknown.

dnl comment here
MACHINE_INCLUDES=$($CC -dumpmachine | $SED "s/-$host_vendor-/-/" | $SED 's/-unknown//')

Providing the --host option to be able to build with clang is from user point of view a bit hard to figure out. I would like to be able to build php using clang with only something like this:

./configure CC=clang

and let those m4 files figure out what other things are needed for clang specifics. (in ideal case scenario of course).

[hughmcmaster]

Thanks for the mention, @petk. Always happy to be involved.

If you want to handle gcc and clang at the same time, you can simply do this:

-  MACHINE_INCLUDES=$($CC -dumpmachine)
+  MACHINE_INCLUDES=$($CC -print-multiarch 2> /dev/null || ($CC -dumpmachine | sed 's/-pc//'))

That said, the detection code in ext/gmp/config.m4 needs an overhaul. AC_CHECK_HEADERS works well, but doesn't provide the path. I'm hoping there is a macro we can use for that, or even write one.

[nikic]

I tried to find a way to do it in autoconf and I couldn't find the proper magic... AC_COMPILE_IFELSE and friends use current compiler settings and there seems to be no good way to see where the include comes from to determine the right GMP_DIR. I checked all other modules and most of them do the same - enumerate directories manually. So I guess we need somebody who understands autoconf better to take a look.

I think there are two different cases here: Manually specified GMP_DIR and use of system libgmp. If system libgmp is used, then both the include path and the lib path should already have the GMP headers / library and actually figuring out what the directories are shouldn't be necessary.

It might be easiest to just split these cases: If a path is specified, check for gmp.h as we do now. If it itsn't then use AC_LINK_IFELSE without any extra -I or -L to ensure both the library and header is found, and add the library without an additional libpath.

[smalyshev]

@hughmcmaster clang add -unknown, not -pc, at least on Travis system. Maybe on some other system it adds -pc too. That's the problem - it's not predictable, really.

It might be easiest to just split these cases

Maybe this is the best way, really.

[hughmcmaster]

If this is urgent, you can filter out the -pc or -unknown part of the string with ($CC -dumpmachine | cut -d '-' -f 1,3-).

I've sent a patch to add pkg-config support to upstream gmp, but it's still going to take time for a new version to appear with this.

[petk]

P.S: the target branch can be here something between PHP-7.2 and 7.4 I think since compiling with clang should be ideally supported.

[nikic]

Merged alternative fix in #4646.