Don't include internal compiler settings with RETAIN_COMPILER_SETTINGS

[sbc100]

This is technically a breaking change so I mentioned it in the ChangeLog.

Fixes: #25663

[juj]

I'll defer to @kripken on this - I do not recall what the context was around adding this feature, and what the usage were.

Might be worth mentioning specific examples in the ChangeLog of which settings in particular will no longer be accessible, that people might have been referring to.

[sbc100]

OK, will wait for @kripken to chime in

[juj]

that people might have been referring to.

The fact that the test code had OPT_LEVEL and DEBUG_LEVEL makes me ponder if those were some of the settings that the users were specifically interested in having. (It is a common motivation to add a test to specifically cover the feature that a user is interested in)

[sbc100]

that people might have been referring to.

The fact that the test code had OPT_LEVEL and DEBUG_LEVEL makes me ponder if those were some of the settings that the users were specifically interested in having. (It is a common motivation to add a test to specifically cover the feature that a user is interested in)

I don't actually know if this feature has any users at all.

It was adding way back in 2014 but without much rational: 153f2d9

I can't find any users with google. There are some users on github .. I'll investigate more.

[sbc100]

It looks like there are 14 users on github: https://github.com/search?q=emscripten_get_compiler_setting%28%22++NOT+path%3Aemscripten.h++NOT+path%3Aemscripten_get_compiler_setting.c&type=code

The settings used are EMSCRIPTEN_VERSION, PTHREAD_POOL_SIZE and LEGACY_GL_EMULATION.

Of these only EMSCRIPTEN_VERSION is an internal settings, so those 2 users would be affected. Maybe we should try to patch them to use runtime detection instead before we land this.

[sbc100]

There are only two uses of EMSCRPITEN_VERSION in the above search and they are both actually same usage: save-editor/source/main.cpp. It also looks like the could both be replaced with __EMSCRIPTEN_xxx__ version macros at compile time.

So I think we should go ahead with this change. The other usages are using non-internal settings.

[sbc100]

OK, I made a carve out for EMSCRIPTEN_VERSION here... so there should be minimal risk of breakages.