[PATCH] D37954: Expand absolute system header paths when using -MD depfiles

[Peter Wu via Phabricator via cfe-commits]

Lekensteyn created this revision.
Herald added a subscriber: klimek.

GCC defaults to expanding the dependencies in depfiles, resolving
components like ".." and symlinks. Mimic this feature to ensure that the
Ninja build tool detects the correct dependencies when a symlink changes
directory levels, see https://github.com/ninja-build/ninja/issues/1330

An option to disable this feature is added in case "these changed header
paths may conflict with some compilation environments", see
https://gcc.gnu.org/ml/gcc-patches/2012-09/msg00287.html

Note that under GCC, this option would also affect the paths shown in
the preprocessed output (-E), but that is not implemented here since I
am not sure if it is useful or breaks something else.


https://reviews.llvm.org/D37954

Files:
  include/clang/Driver/Options.td
  include/clang/Frontend/DependencyOutputOptions.h
  lib/Driver/Job.cpp
  lib/Driver/ToolChains/Clang.cpp
  lib/Frontend/CompilerInvocation.cpp
  lib/Frontend/DependencyFile.cpp
  lib/Tooling/ArgumentsAdjusters.cpp
  test/Preprocessor/dependencies-realpath.c

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