Implements PR40180.
clang-cl has one minor behavior difference with cl with this change.
Clang allows the user to enable the C++17 feature of aligned allocation
without enabling all of C++17, but MSVC will not call the aligned
allocation overloads unless -std:c++17 is passed. While our behavior is
technically incompatible, it would require making driver mode specific
changes to match MSVC precisely, and clang's behavior is useful because
it allows people to experiment with new C++17 features individually.
Therefore, I plan to leave it as is.
llvm-svn: 351249
* /Zc:trigraphs and /Zc:trigraphs- are now honored
* /Zc:strictStrings is now honored
* /Zc:auto is now honored/ignored (clang does the Right Thing for this already)
Also add a dedicated test for the various /Zc: flags.
clang-cl doesn't always agree with cl.exe on the default values for /Zc flags.
For example, I think clang always behaves as if /Zc:inline is passed, and
warns if the user explicitly passes /Zc:inline-
Fixes PR21974.
llvm-svn: 224791
Reid Kleckner