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[MSVC] Don't add -nostdinc++ -isystem to runtimes builds

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If the host compiler is MSVC or clang-cl, then the compiler used to
buidl the runtimes will be clang-cl, and it doesn't support either of
those flags.

Worse, because -isystem is a space separated flag, it causes all cmake
try_compile tests to fail, so none of the -Wno-* flags make it to the
compiler in libcxx. I noticed that we weren't passing
-Wno-user-defined-literals to clang-cl and were getting warnings in the
build, and this fixes that for me.

Differential Revision: https://reviews.llvm.org/D94817
This commit is contained in:
Reid Kleckner 2021-01-15 12:35:42 -08:00
parent 6a42cbf6d2
commit 98c89ccfbd
1 changed files with 8 additions and 5 deletions
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11
runtimes/CMakeLists.txt
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@ -77,12 +77,15 @@ endif()
include(CheckLibraryExists)
include(CheckCCompilerFlag)
# We don't have libc++ (yet)...
set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -nostdinc++ -nostdlib++")
# Disable use of the installed C++ standard library when building runtimes. If
# MSVC is true, we must be using the clang-cl driver, which doesn't understand
# these flags.
if (NOT MSVC)
set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -nostdinc++ -nostdlib++")
# ...but we need access to libc++ headers for CMake checks to succeed.
if (LLVM_EXTERNAL_LIBCXX_SOURCE_DIR AND "libcxx" IN_LIST LLVM_ENABLE_RUNTIMES)
if (LLVM_EXTERNAL_LIBCXX_SOURCE_DIR AND "libcxx" IN_LIST LLVM_ENABLE_RUNTIMES)
set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -isystem ${LLVM_EXTERNAL_LIBCXX_SOURCE_DIR}/include")
endif()
endif()
# Avoid checking whether the compiler is working.