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[release/8.0-staging] Add flags when the clang's major version is > 20.0 #121150

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[release/8.0-staging] Add flags when the clang's major version is > 20.0 #121150

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Add flags when the clang's major version is > 20.0
AaronRobinsonMSFT Oct 28, 2025
27850df
Additional changes.
AaronRobinsonMSFT Oct 29, 2025
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18 changes: 15 additions & 3 deletions eng/native/configurecompiler.cmake
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Expand Up @@ -500,9 +500,21 @@ if (CLR_CMAKE_HOST_UNIX)
#-fms-compatibility Enable full Microsoft Visual C++ compatibility
#-fms-extensions Accept some non-standard constructs supported by the Microsoft compiler

# Make signed arithmetic overflow of addition, subtraction, and multiplication wrap around
# using twos-complement representation (this is normally undefined according to the C++ spec).
add_compile_options(-fwrapv)
if((CMAKE_C_COMPILER_ID STREQUAL "Clang" AND CMAKE_C_COMPILER_VERSION VERSION_GREATER_EQUAL 20.0) OR
(CMAKE_CXX_COMPILER_ID STREQUAL "Clang" AND CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL 20.0))
Comment on lines +503 to +504
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Any concern here about Clang on macOS? If so, this should use MATCHES instead of STREQUAL.

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I don't think we care about macOS for these changes. Is there doc on why to use MATCHES vs STREQUAL in this case? Is it "clang" on macOS?

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On macOS, it's AppleClang instead of Clang (as Apple has their forked build with slight differences).

# Make signed overflow well-defined. Implies the following flags in clang-20 and above.
# -fwrapv - Make signed arithmetic overflow of addition, subtraction, and multiplication wrap around
# using twos-complement representation (this is normally undefined according to the C++ spec).
# -fwrapv-pointer - The same as -fwrapv but for pointers.
add_compile_options(-fno-strict-overflow)

# Suppress C++ strict aliasing rules. This matches our use of MSVC.
add_compile_options(-fno-strict-aliasing)
else()
# Make signed arithmetic overflow of addition, subtraction, and multiplication wrap around
# using twos-complement representation (this is normally undefined according to the C++ spec).
add_compile_options(-fwrapv)
endif()

if(CLR_CMAKE_HOST_APPLE)
# Clang will by default emit objc_msgSend stubs in Xcode 14, which ld from earlier Xcodes doesn't understand.
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