Add -export_dynamic flag for AppleDynamicLinker

[wolfgangwalther]

The apple linker uses -export_dynamic instead of --export-dynamic 1. This should be set when setting export_dynamic: true.

Resolves #13290

[wolfgangwalther]

I assume the two CI failures are not related - all other PRs seem to have them, too.

[tristan957]

Any idea if this has been the case for every version of the linker? Or has Meson just been wrong the whole time?

[wolfgangwalther]

Any idea if this has been the case for every version of the linker? Or has Meson just been wrong the whole time?

There's more on that in the thread here: https://www.postgresql.org/message-id/flat/427c7c25-e8e1-4fc5-a1fb-01ceff185e5b%40technowledgy.de

So essentially:

• This flag is more important on Linux / GNU / LLVM, because those symbols are not exported by default here. So even without -flto this is required there. This part, meson has been doing.
• Apple's linker does export them by default already, so many cases are covered - but not anymore with -flto.
• This was introduced in ld64-224.1 around the year 2011. This is the first man page it appears in.

So yes, meson has not been covering this case for a while.

[tristan957]

Thanks for that awesome write up.

[barracuda156]

@wolfgangwalther @tristan957 Is it possible to make this conditional on the macOS version being 10.7+? This flag is not supported on 10.6 and below, and adding it breaks the build of anything where it is appended. glib2 is broken now on 10.6, for example: https://trac.macports.org/ticket/70386

[tristan957]

Yes. Please submit a PR

[barracuda156]

@tristan957 Could you say how to check for [build] macOS version?

[tristan957]

The class has a version attribute/function most likely. You can then do a version comparison.

[wolfgangwalther]

This flag is not supported on 10.6 and below

10.7 was released in July 2011, which matches my observation from above:

This was introduced in ld64-224.1 around the year 2011. This is the first man page it appears in.

I opened #13557 to fix it.