https://github.com/zeux created https://github.com/llvm/llvm-project/pull/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. >From 357a21c38c1036a012affc85026fcba376ab7128 Mon Sep 17 00:00:00 2001 From: Arseny Kapoulkine <arseny.kapoulk...@gmail.com> Date: Sun, 15 Oct 2023 13:20:31 -0700 Subject: [PATCH] [Sema] -Wzero-as-null-pointer-constant: don't warn for __null 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. Note: a limitation of this change is that we will still warn on use of NULL when it is defined as 0, which could be a problem for clang-cl. --- clang/lib/Sema/Sema.cpp | 8 +++++++- clang/test/SemaCXX/warn-zero-nullptr.cpp | 8 ++++---- 2 files changed, 11 insertions(+), 5 deletions(-) diff --git a/clang/lib/Sema/Sema.cpp b/clang/lib/Sema/Sema.cpp index 67533ccbdf347c7..acb765559e6a8d4 100644 --- a/clang/lib/Sema/Sema.cpp +++ b/clang/lib/Sema/Sema.cpp @@ -590,7 +590,11 @@ void Sema::diagnoseZeroToNullptrConversion(CastKind Kind, const Expr *E) { if (Kind != CK_NullToPointer && Kind != CK_NullToMemberPointer) return; - if (E->IgnoreParenImpCasts()->getType()->isNullPtrType()) + + const Expr *EStripped = E->IgnoreParenImpCasts(); + if (EStripped->getType()->isNullPtrType()) + return; + if (isa<GNUNullExpr>(EStripped)) return; if (Diags.isIgnored(diag::warn_zero_as_null_pointer_constant, @@ -612,6 +616,8 @@ void Sema::diagnoseZeroToNullptrConversion(CastKind Kind, const Expr *E) { // If it is a macro from system header, and if the macro name is not "NULL", // do not warn. + // Note that uses of "NULL" will be ignored above on systems that define it + // as __null. SourceLocation MaybeMacroLoc = E->getBeginLoc(); if (Diags.getSuppressSystemWarnings() && SourceMgr.isInSystemMacro(MaybeMacroLoc) && diff --git a/clang/test/SemaCXX/warn-zero-nullptr.cpp b/clang/test/SemaCXX/warn-zero-nullptr.cpp index 45f05fa5703b1c3..684572f8ef67d05 100644 --- a/clang/test/SemaCXX/warn-zero-nullptr.cpp +++ b/clang/test/SemaCXX/warn-zero-nullptr.cpp @@ -16,10 +16,10 @@ int (S::*mp1) = 0; // expected-warning{{zero as null pointer constant}} void (*fp1)() = 0; // expected-warning{{zero as null pointer constant}} void* p1 = 0; // expected-warning{{zero as null pointer constant}} -// NULL is an integer constant expression, so warn on it too: -void* p2 = __null; // expected-warning{{zero as null pointer constant}} -void (*fp2)() = __null; // expected-warning{{zero as null pointer constant}} -int (S::*mp2) = __null; // expected-warning{{zero as null pointer constant}} +// __null is not treated as an integer constant expression for GCC compatibility +void* p2 = __null; +void (*fp2)() = __null; +int (S::*mp2) = __null; void f0(void* v = MACRO); // expected-warning{{zero as null pointer constant}} void f1(void* v = NULL); // expected-warning{{zero as null pointer constant}} _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
