Copilot commented on code in PR #50979:
URL: https://github.com/apache/arrow/pull/50979#discussion_r3850188713
##########
cpp/cmake_modules/SetupCxxFlags.cmake:
##########
@@ -218,22 +218,11 @@ if(WIN32)
set(CXX_COMMON_FLAGS "/W3 /EHsc")
endif()
- # Disable C5105 (macro expansion producing 'defined' has undefined
- # behavior) warning because there are codes that produce this
- # warning in Windows Kits. e.g.:
- #
- # #define _CRT_INTERNAL_NONSTDC_NAMES
\
- # (
\
- # ( defined _CRT_DECLARE_NONSTDC_NAMES &&
_CRT_DECLARE_NONSTDC_NAMES) || \
- # (!defined _CRT_DECLARE_NONSTDC_NAMES && !__STDC__
) \
- # )
+ # Enable the conforming preprocessor to support C++20 features.
#
# See also:
- # * C5105:
https://docs.microsoft.com/en-US/cpp/error-messages/compiler-warnings/c5105
- # * Related reports:
- # *
https://developercommunity.visualstudio.com/content/problem/387684/c5105-with-stdioh-and-experimentalpreprocessor.html
- # *
https://developercommunity.visualstudio.com/content/problem/1249671/stdc17-generates-warning-compiling-windowsh.html
- set(CXX_COMMON_FLAGS "${CXX_COMMON_FLAGS} /wd5105")
+ # *
https://devblogs.microsoft.com/cppblog/announcing-full-support-for-a-c-c-conformant-preprocessor-in-msvc/
+ set(CXX_COMMON_FLAGS "${CXX_COMMON_FLAGS} /Zc:preprocessor")
Review Comment:
Enabling `/Zc:preprocessor` does not remove C5105 for Windows SDKs that
still expand `defined` from a macro; those headers are the reason this
suppression was present. Because Debug builds add `/WX` in this file, users
with such an SDK can now fail when including Windows headers. Please retain
`/wd5105` (or gate its removal on a supported SDK version).
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