LLVM artifacts with/without asserts have different ABIBreakingChecks

[maleadt]

$ objdump -t /tmp/libLLVM_assert.v11.0.1.x86_64-linux-gnu-cxx11/lib/libLLVM-11.0.1jl.so | grep ABIBreakingChecks
0000000004eeeeb0 g     O .bss   0000000000000004              _ZN4llvm23EnableABIBreakingChecksE
$ objdump -t /tmp/libLLVM.v11.0.1.x86_64-linux-gnu-cxx11/lib/libLLVM-11.0.1jl.so | grep ABIBreakingChecks
0000000003e9ec30 g     O .bss   0000000000000004              _ZN4llvm24DisableABIBreakingChecksE

This breaks libLLVM-based artifacts when using LLVM+asserts:

ERROR: LoadError: InitError: could not load library "/home/tim/Julia/depot/artifacts/769012422c18bf09c53376e964a7fb286d1799c8/lib/libLLVMSPIRVLib.so"
/home/tim/Julia/depot/artifacts/769012422c18bf09c53376e964a7fb286d1799c8/lib/libLLVMSPIRVLib.so: undefined symbol: _ZN4llvm24DisableABIBreakingChecksE, version JL_LLVM_11.0

I guess we should set LLVM_ABI_BREAKING_CHECKS to either FORCE_ON or FORCE_OFF:

LLVM_ABI_BREAKING_CHECKS:STRING

Used to decide if LLVM should be built with ABI breaking checks or not. Allowed values are WITH_ASSERTS (default), FORCE_ON and FORCE_OFF. WITH_ASSERTS turns on ABI breaking checks in an assertion enabled build. FORCE_ON (FORCE_OFF) turns them on (off) irrespective of whether normal (NDEBUG-based) assertions are enabled or not. A version of LLVM built with ABI breaking checks is not ABI compatible with a version built without it.

[vtjnash]

That seems intentional, since it literally is warning you that the ABI is incompatible? (the layout of some critical objects changes)

[maleadt]

It wasn't clear to me whether the ABI is actually incompatible between release/asserts builds, or whether the link-time check for this is just enabled when doing asserts builds. But yeah, it turns out to be the former, which implies we'll need asserts-versions of all of these artifacts... 🙁

@staticfloat Is this something #35193 would include, i.e., would the assertion-ness be discoverable from the libLLVM_jll stdlib (for use by, e.g., a Pkg hook to select the LLVM asserts-based build of any dependency)?

[staticfloat]

I haven't thought that far ahead yet. What are the ramifications? Will we have to rebuild everything that links against libLLVM? That seems.... untenable to me.

[maleadt]

Will we have to rebuild everything that links against libLLVM? That seems.... untenable to me.

Probably. As Jameson mentions, and e.g. https://lists.llvm.org/pipermail/llvm-dev/2016-November/107148.html confirms, asserts builds are ABI incompatible with release builds.