[cherry-pick stable/20230725] [Sema] -Wzero-as-null-pointer-constant: don't warn for __null (#69126) #8223
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… don't warn for __null (llvm#69126) The implementation of -Wzero-as-null-pointer-constant was done before the following fix has been committed to GCC: https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=752e7593b0f19af233a0b7e72daab8413662b605;hp=298434c916c14e8adca2cab8a746aee29038c5b3 As a result, clang and gcc diverge on the use of `__null` and, consequently, on the use of `NULL` on systems like Linux/macOS where `NULL` is defined as `__null`. This is a problem for compatibility between gcc and clang, particularly for code bases that support C++98 or for single-source libraries that are implemented in C, but compiled as C++ via inclusion into a C++ translation unit. Code like this can not be changed to use `nullptr`, as it needs to maintain compatibility with C before C23 or C++ before C++11, but warns on the use of `NULL` in clang. The warning `Wzero-as-null-pointer-constant` is still useful with this change, as it allows to change `0` to `NULL`, which fixes gcc warnings and helps the reader distinguish between pointers and non-pointers. Users who require a full C++11 modernization pass can still use clang-tidy for that purpose.
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ributzka
approved these changes
Feb 16, 2024
Bigcheese
approved these changes
Feb 16, 2024
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The implementation of -Wzero-as-null-pointer-constant was done before the following fix has been committed to GCC:
https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=752e7593b0f19af233a0b7e72daab8413662b605;hp=298434c916c14e8adca2cab8a746aee29038c5b3
As a result, clang and gcc diverge on the use of
__nulland, consequently, on the use ofNULLon systems like Linux/macOS whereNULLis defined as__null.This is a problem for compatibility between gcc and clang, particularly for code bases that support C++98 or for single-source libraries that are implemented in C, but compiled as C++ via inclusion into a C++ translation unit. Code like this can not be changed to use
nullptr, as it needs to maintain compatibility with C before C23 or C++ before C++11, but warns on the use ofNULLin clang.The warning
Wzero-as-null-pointer-constantis still useful with this change, as it allows to change0toNULL, which fixes gcc warnings and helps the reader distinguish between pointers and non-pointers. Users who require a full C++11 modernization pass can still use clang-tidy for that purpose.