[PATCH] D132444: [clang] Allow using -rtlib=platform to switching to the default rtlib on all targets

Tue Aug 23 04:35:58 PDT 2022

mstorsjo added a comment.

In D132444#3742305 <https://reviews.llvm.org/D132444#3742305>, @mstorsjo wrote:

> In D132444#3742295 <https://reviews.llvm.org/D132444#3742295>, @thakis wrote:
>
>> Do we have precedent for "platform" for this? For fuse-ld=, one is supposed to use `-fuse-ld=` (without anything after the `=`) to get the default ld. That's not great (...but it can't collide with actual linker names, i suppose).
>>
>> Using "platform" (or any other self-descriptive name) for this seems easier to understand than passing an empty value. But it'd be nice if we could use this consistently in our various flags.
>
> Yes, `"platform"` is an existing option handled in a bunch of places already - see e.g. https://github.com/llvm/llvm-project/blob/main/clang/lib/Driver/ToolChain.cpp#L832-L838. It's just that these cases hadn't been updated to take it into account.

Then again, the quoted code comment says that `"platform"` only is meant to be used for overriding `CLANG_DEFAULT_RTLIB` in tests, but I don't see why one can't use it for overriding `CLANG_DEFAULT_RTLIB` (or an earlier `-rtlib` option on the command line) in real world uses too. (I had a user wanting to use my builds of clang for MSVC use cases, where it failed due to my Clang defaulting to `-rtlib=compiler-rt`, with no way of overriding it back to default, see https://github.com/mstorsjo/llvm-mingw/issues/267)

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