[PATCH] D100755: [llvm-rc] [3/4] Run clang to preprocess input files

[Martin Storsjö via Phabricator via llvm-commits]

mstorsjo added a comment.

In D100755#2699721 <https://reviews.llvm.org/D100755#2699721>, @amccarth wrote:

> I'm not quite clear on the motivation.  It's hard for me to imagine the resource compiler being useful if you cannot use the C preprocessor.  I guess for simple tests you don't need it, is that worth adding an option?

It's mostly due to the layering issue; when running `check-llvm` one doesn't necessarily have clang available (and I guess it's not ok to add such a dependency). That unfortunately makes the actual invocation of the subprocess untested by the unit tests.

Secondly, as llvm-rc currently doesn't rely on clang, one could concievably have setups that use llvm-rc without clang available, and would want to keep it that way at least initially. (E.g. my current windres wrapper preprocesses externally and then calls llvm-rc. It does have 'clang' available, but not e.g. 'clang-cl'. With patch 4/4 in place I don't need my external wrapper - but it'd still be used while transitioning to this setup.)


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