[PATCH] D24809: [libcxx] [cmake] Stop stripping -m32 from compiler flags

[Eric Fiselier via cfe-commits]

EricWF added a comment.

> Stop stripping -m32 from the user-supplied flags. There is no valid reason to do that, stripping it silently is thoroughly confusing and makes it impossible to do distribution multi-ABI builds without resorting to ugly hacks.


The reason for stripping it is configurations like `-DLLVM_BUILD_32_BITS=ON -DLIBCXX_BUILD_32_BITS=OFF`, where we inherit the incorrect set of flags from the LLVM parent project. I understand your frustration with this behavior but I'm not sure how else to handle that.

> Otherwise, in order to perform 32-bit builds the build scripts would have to use LIBCXX_BUILD_32_BITS. However, -m32 is only one of the many different ABI flags for different targets, and it really makes no sense to add separate CMake options for each possible -m* flag and then keep a mapping from well-known flags to the custom CMake options.


I don't see how using `-DLLVM_BUILD_32_BITS=ON` is impossible compared to using `-DCMAKE_CXX_FLAGS=-m32`, but the fact it acts differently than other ABI flags is unfortunate.

I'm not sure what the correct thing to do is. Does anybody else want to weigh in?


https://reviews.llvm.org/D24809