[llvm] 401dee4 - Reapply "[cmake][msvc] Enable standards-conforming preprocessor"

[Jan Svoboda via llvm-commits]

Author: Jan Svoboda
Date: 2023-02-08T13:47:58-08:00
New Revision: 401dee445196a4a97b2ad2ca7cfc125b776be7f3

URL: https://github.com/llvm/llvm-project/commit/401dee445196a4a97b2ad2ca7cfc125b776be7f3
DIFF: https://github.com/llvm/llvm-project/commit/401dee445196a4a97b2ad2ca7cfc125b776be7f3.diff

LOG: Reapply "[cmake][msvc] Enable standards-conforming preprocessor"

This reverts commit 16e1a49441c51817697138437d8db2c15bc19cb4, essentially reapplying 12d8e7c6ade55bba241259312e3e4bdcf6aeab81. The build bot where this caused issues is supposed to be updated now: https://reviews.llvm.org/D135128#4108588

Added: 
    

Modified: 
    llvm/cmake/modules/HandleLLVMOptions.cmake

Removed: 
    


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diff  --git a/llvm/cmake/modules/HandleLLVMOptions.cmake b/llvm/cmake/modules/HandleLLVMOptions.cmake
index 7173e2724097a..7d65304b2ac77 100644
--- a/llvm/cmake/modules/HandleLLVMOptions.cmake
+++ b/llvm/cmake/modules/HandleLLVMOptions.cmake
@@ -494,6 +494,10 @@ if( MSVC )
 
   append("/Zc:inline" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
 
+  # Enable standards-conforming preprocessor.
+  # https://learn.microsoft.com/en-us/cpp/build/reference/zc-preprocessor
+  append("/Zc:preprocessor" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
+
   # Some projects use the __cplusplus preprocessor macro to check support for
   # a particular version of the C++ standard. When this option is not specified
   # explicitly, macro's value is "199711L" that implies C++98 Standard.