[PATCH] D47480: clang-cl: Expose -no-canonical-prefixes

[Nico Weber via Phabricator via cfe-commits]

thakis created this revision.
thakis added a reviewer: rnk.

-no-canonical-prefixes is a weird flag: In gcc, it controls whether realpath() is called on the path of the driver binary. It's needed to support some usecases where gcc is symlinked to, see https://gcc.gnu.org/ml/gcc/2011-01/msg00429.html for some background.

In clang, the resource dir is found relative to the compiler binary, and without -no-canonical-prefixes that's an absolute path. For clang, the main use case for -no-canonical-prefixes is to make the -resource-dir path added by the driver relative instead of absolute. Making it relative seems like the better default, but since neither clang not gcc have -canonical-prefixes without no- which makes changing the default tricky, and since some symlink behaviors do depend on the realpath() call at least for gcc, just expose -no-canonical-prefixes in clang-cl mode.

Alternatively we could default to no-canonical-prefix-mode for clang-cl since it's less likely to be used in symlinked scenarios, but since you already need to about -no-canonical-prefixes for the non-clang-cl bits of your build, not hooking this of driver mode seems better to me.


https://reviews.llvm.org/D47480

Files:
  include/clang/Driver/Options.td
  test/Driver/cl-options.c


Index: include/clang/Driver/Options.td
===================================================================
--- include/clang/Driver/Options.td
+++ include/clang/Driver/Options.td
@@ -2251,7 +2251,7 @@
 def multiply__defined__unused : Separate<["-"], "multiply_defined_unused">;
 def multiply__defined : Separate<["-"], "multiply_defined">;
 def mwarn_nonportable_cfstrings : Flag<["-"], "mwarn-nonportable-cfstrings">, Group<m_Group>;
-def no_canonical_prefixes : Flag<["-"], "no-canonical-prefixes">, Flags<[HelpHidden]>,
+def no_canonical_prefixes : Flag<["-"], "no-canonical-prefixes">, Flags<[HelpHidden, CoreOption]>,
   HelpText<"Use relative instead of canonical paths">;
 def no_cpp_precomp : Flag<["-"], "no-cpp-precomp">, Group<clang_ignored_f_Group>;
 def no_integrated_cpp : Flag<["-", "--"], "no-integrated-cpp">, Flags<[DriverOption]>;
Index: test/Driver/cl-options.c
===================================================================
--- test/Driver/cl-options.c
+++ test/Driver/cl-options.c
@@ -591,6 +591,8 @@
 // RUN:     -flimit-debug-info \
 // RUN:     -flto \
 // RUN:     -fmerge-all-constants \
+// RUN:     -no-canonical-prefixes \
+// RUN:     -fno-coverage-mapping \
 // RUN:     --version \
 // RUN:     -Werror /Zs -- %s 2>&1
 


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