Use CMAKE_SYSROOT instead of EMSCRIPTEN_SYSROOT

[xinitrcn1]

No description provided.

[sbc100]

I think the reason we don't do this is that emcc on it own already automatically includes the sysroot.

i.e. you never need to do emcc --sysroot=/path/to/emscripten/sysroot since emcc already knows exactly where its sysroot is. Its not something we expect user to pass.

I think we don't really want cmake to inject and additional --sysroot since it would be redundant.

[sbc100]

If we set the compiler to clang then it would make sense to pass things like --sysroot and --target=wasm32-unknown-emscripten, but when we use the emcc wrapper around clang they are not needed.

[xinitrcn1]

I'm aware emcc itself uses --sysroot..

HOWEVER
many projects use ${CMAKE_SYSROOT} for other miscellany purpouses, most notably:

• pkg search
• pkgconfig
• find package
• checks
• unholy usages of "absolute paths" that depend on ${CMAKE_SYSROOT}

For example shadPS4 uses CMAKE_SYSROOT for checks and stuff, is it bad design? No! As per documentation CMAKE_SYSROOT MUST point to a valid sysroot, otherwise it's not a valid toolchain.

[sbc100]

For find package we set CMAKE_FIND_ROOT_PATH.

For pkg_config we set PKG_CONFIG_LIBDIR.

As I said, I'm to to keem on the idea of seeing --sysroot=/path/to/default/sysroot added to every emcc command line that cmake generates.

@bradking, sorry to loop you in again here, but I'm not sure what the best approach is here. We do use a sysroot, but its location is already know the emcc. I guess I'm looking for way to tell cmake about the sysroot without injecting superfluous/redundant compiler flags. Is that something is possible? Are we wrong to not set CMAKE_SYSROOT?

[sbc100]

Maybe something like DEFAULT_SYSROOT which would allow cmake to be aware or it without having to also inject --sysroot?

[xinitrcn1]

Nonstandard and as I mentioned above will break any projects which rightfully assume CMAKE_SYSROOT points to the actual sysroot

[xinitrcn1]

Additionally, I'm pretty sure that the extra appended sysroot would be a no-op in most cases.

Even if so, I'd know that conforming to the expected set variables of CMake would be far more ideal than trying to use nonstandard.

For example I know a lot of projects who try to use assembly files because cmake's processor variable is set to the host instead of... well... something reasonable like "wasm64".

It's mostly due to the fact a lot of existing projects rightfully assume CMake provides accurate variables to the environment, what Emscripten is doing in this case is give a "half-answer" for most variables.

Of my particular note is CMAKE_SYSTEM_PROCESSOR (affects boost context, containers) and CMAKE_SYSROOT (shadPS4, openssl-cmakel) to metnion a few