Author: Aaron Ballman Date: 2025-04-15T12:21:04-04:00 New Revision: ece10a64cb180ba931b60cbd939d80412973eada
URL: https://github.com/llvm/llvm-project/commit/ece10a64cb180ba931b60cbd939d80412973eada DIFF: https://github.com/llvm/llvm-project/commit/ece10a64cb180ba931b60cbd939d80412973eada.diff LOG: Allow some attributes on declarations after definitions (#135791) The deprecated, maybe_unused, and nodiscard standard attributes may all be applied to a redeclaration after a definition has already appeared. We were previously dropping the attribute in that case, now we retain the attribute after the redeclaration. Note: someday we may want to tablegen this as part of information from Attr.td. We may also want to relax the restriction here so that the syntax used does not matter. This is an intentionally conservative fix. Fixes #135481 Added: clang/test/Sema/attr-decl-after-definition-std.c Modified: clang/docs/ReleaseNotes.rst clang/lib/Sema/SemaDecl.cpp Removed: ################################################################################ diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst index c106148855436..e63de32a0b2aa 100644 --- a/clang/docs/ReleaseNotes.rst +++ b/clang/docs/ReleaseNotes.rst @@ -439,6 +439,11 @@ Bug Fixes to Attribute Support - No longer crashing on ``__attribute__((align_value(N)))`` during template instantiation when the function parameter type is not a pointer or reference. (#GH26612) +- Now allowing the ``[[deprecated]]``, ``[[maybe_unused]]``, and + ``[[nodiscard]]`` to be applied to a redeclaration after a definition in both + C and C++ mode for the standard spellings (other spellings, such as + ``__attribute__((unused))`` are still ignored after the definition, though + this behavior may be relaxed in the future). (#GH135481) Bug Fixes to C++ Support ^^^^^^^^^^^^^^^^^^^^^^^^ diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp index e9805c345b6af..240ce5391af81 100644 --- a/clang/lib/Sema/SemaDecl.cpp +++ b/clang/lib/Sema/SemaDecl.cpp @@ -2996,6 +2996,21 @@ static void checkNewAttributesAfterDef(Sema &S, Decl *New, const Decl *Old) { // msvc will allow a subsequent definition to add an uuid to a class ++I; continue; + } else if (isa<DeprecatedAttr, WarnUnusedResultAttr, UnusedAttr>( + NewAttribute) && + NewAttribute->isStandardAttributeSyntax()) { + // C++14 [dcl.attr.deprecated]p3: A name or entity declared without the + // deprecated attribute can later be re-declared with the attribute and + // vice-versa. + // C++17 [dcl.attr.unused]p4: A name or entity declared without the + // maybe_unused attribute can later be redeclared with the attribute and + // vice versa. + // C++20 [dcl.attr.nodiscard]p2: A name or entity declared without the + // nodiscard attribute can later be redeclared with the attribute and + // vice-versa. + // C23 6.7.13.3p3, 6.7.13.4p3. and 6.7.13.5p5 give the same allowances. + ++I; + continue; } else if (const AlignedAttr *AA = dyn_cast<AlignedAttr>(NewAttribute)) { if (AA->isAlignas()) { // C++11 [dcl.align]p6: diff --git a/clang/test/Sema/attr-decl-after-definition-std.c b/clang/test/Sema/attr-decl-after-definition-std.c new file mode 100644 index 0000000000000..bab52b4dd97ad --- /dev/null +++ b/clang/test/Sema/attr-decl-after-definition-std.c @@ -0,0 +1,41 @@ +// RUN: %clang_cc1 -fsyntax-only -Wignored-attributes -verify -std=c23 %s +// RUN: %clang_cc1 -fsyntax-only -Wignored-attributes -verify -x c++ %s +// RUN: %clang_cc1 -fsyntax-only -ast-dump %s | FileCheck %s + +inline int frob(int x) { return x; } + +[[deprecated]] int frob(int); // expected-note 2 {{'frob' has been explicitly marked deprecated here}} + +void use1() { + // Using this should give a deprecation warning, but not a nodiscard warning. + frob(0); // expected-warning {{'frob' is deprecated}} +} + +[[nodiscard]] int frob(int); + +void use2() { + // This should give both warnings. + frob(0); // expected-warning {{'frob' is deprecated}} \ + expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} +} + +[[maybe_unused]] int frob(int); + +// Currently, this is only allowed for the standard spelling of the attributes. +void blob() {} // expected-note {{previous definition is here}} +__attribute__((deprecated)) void blob(); // expected-warning {{attribute declaration must precede definition}} + +// CHECK: FunctionDecl {{.*}} frob + +// CHECK: FunctionDecl {{.*}} prev {{.*}} frob +// CHECK: DeprecatedAttr + +// CHECK: FunctionDecl {{.*}} prev {{.*}} frob +// CHECK: DeprecatedAttr +// CHECK: WarnUnusedResultAttr + +// CHECK: FunctionDecl {{.*}} prev {{.*}} frob +// CHECK: DeprecatedAttr +// CHECK: WarnUnusedResultAttr +// CHECK: UnusedAttr + _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
