[PATCH] D149187: [clang] Canonicalize system headers in dependency file when -canonical-prefixes

[Arthur Eubanks via Phabricator via cfe-commits]

aeubanks created this revision.
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Clang was writing paths to the dependency file that don't exist when using a sysroot with symlinks, causing everything to get rebuilt every time. This is reproducible on Linux by creating a symlink to '/', using that as the sysroot, and trying to build something with ninja that includes the C++ stdlib (e.g. a typical build of LLVM).

This fixes https://github.com/ninja-build/ninja/issues/1330 and somewhat matches gcc.

gcc canonicalizes system headers in dependency files under a -f[no-]canonical-system-headers, but it makes more sense to look at -canonical-prefixes.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D149187

Files:
  clang/include/clang/Driver/Options.td
  clang/include/clang/Frontend/DependencyOutputOptions.h
  clang/include/clang/Frontend/Utils.h
  clang/lib/Driver/ToolChains/Clang.cpp
  clang/lib/Frontend/DependencyFile.cpp
  clang/test/Driver/canonical-system-headers.c
  clang/test/Preprocessor/Inputs/canonical-system-headers/a.h
  clang/test/Preprocessor/canonical-system-headers.c

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