[libcxx-commits] [libcxx] 1540646 - [libcxx] Don't add -Wall when building in MSVC mode

[Martin Storsjö via libcxx-commits]

Author: Martin Storsjö
Date: 2021-03-05T23:48:02+02:00
New Revision: 1540646dbd18b7d7637a9f8ba64b53e0417ff5e4

URL: https://github.com/llvm/llvm-project/commit/1540646dbd18b7d7637a9f8ba64b53e0417ff5e4
DIFF: https://github.com/llvm/llvm-project/commit/1540646dbd18b7d7637a9f8ba64b53e0417ff5e4.diff

LOG: [libcxx] Don't add -Wall when building in MSVC mode

The MSVC -Wall (or /Wall) option maps (in clang-cl) to the GCC style
option -Weverything, which we don't really want. Instead use -W4 which
is the corresponding MSVC option.

This silences the build with clang-cl, which previously used to
output 100 warnings per translation unit.

Differential Revision: https://reviews.llvm.org/D98035

Added: 
    

Modified: 
    libcxx/CMakeLists.txt

Removed: 
    


################################################################################
diff  --git a/libcxx/CMakeLists.txt b/libcxx/CMakeLists.txt
index 3599bcde6d66..708405363500 100644
--- a/libcxx/CMakeLists.txt
+++ b/libcxx/CMakeLists.txt
@@ -572,7 +572,14 @@ endfunction()
 # Warning flags ===============================================================
 function(cxx_add_warning_flags target)
   target_compile_definitions(${target} PUBLIC -D_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
-  target_add_compile_flags_if_supported(${target} PRIVATE -Wall -Wextra -W -Wwrite-strings
+  if (MSVC)
+    # -W4 is the cl.exe/clang-cl equivalent of -Wall. (In cl.exe and clang-cl,
+    # -Wall is equivalent to -Weverything in GCC style compiler drivers.)
+    target_add_compile_flags_if_supported(${target} PRIVATE -W4)
+  else()
+    target_add_compile_flags_if_supported(${target} PRIVATE -Wall)
+  endif()
+  target_add_compile_flags_if_supported(${target} PRIVATE -Wextra -W -Wwrite-strings
                                                           -Wno-unused-parameter -Wno-long-long
                                                           -Werror=return-type -Wextra-semi)
   if ("${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang")