Author: Oleksandr T. Date: 2025-03-19T23:06:10+02:00 New Revision: 01d28c1cd7862fb75c8e353b2b18d13f9801b327
URL: https://github.com/llvm/llvm-project/commit/01d28c1cd7862fb75c8e353b2b18d13f9801b327 DIFF: https://github.com/llvm/llvm-project/commit/01d28c1cd7862fb75c8e353b2b18d13f9801b327.diff LOG: [Clang] emit -Wunused-variable warning for unused structured bindings without the [[maybe_unused]] attribute (#127061) Fixes #125810 --- This patch resolves an issue in Clang where the `-Wunused-variable` warning was suppressed for structured bindings with elements marked `[[maybe_unused]]`, causing the entire declaration to be treated as used and preventing the warning from being emitted. Added: clang/test/SemaCXX/unused-bindings.cpp Modified: clang/docs/ReleaseNotes.rst clang/lib/Sema/SemaDecl.cpp clang/test/SemaCXX/unused.cpp Removed: ################################################################################ diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst index 0af4f71dfbac9..9b0680c68b83a 100644 --- a/clang/docs/ReleaseNotes.rst +++ b/clang/docs/ReleaseNotes.rst @@ -348,6 +348,8 @@ Bug Fixes to C++ Support - Correctly diagnoses if unresolved using declarations shadows template paramters (#GH129411) - Clang was previously coalescing volatile writes to members of volatile base class subobjects. The issue has been addressed by propagating qualifiers during derived-to-base conversions in the AST. (#GH127824) +- Clang now emits the ``-Wunused-variable`` warning when some structured bindings are unused + and the ``[[maybe_unused]]`` attribute is not applied. (#GH125810) Bug Fixes to AST Handling ^^^^^^^^^^^^^^^^^^^^^^^^^ diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp index 61e3cd4066a8d..fdfba48ab4b1c 100644 --- a/clang/lib/Sema/SemaDecl.cpp +++ b/clang/lib/Sema/SemaDecl.cpp @@ -1934,13 +1934,14 @@ static bool ShouldDiagnoseUnusedDecl(const LangOptions &LangOpts, // For a decomposition declaration, warn if none of the bindings are // referenced, instead of if the variable itself is referenced (which // it is, by the bindings' expressions). - bool IsAllPlaceholders = true; + bool IsAllIgnored = true; for (const auto *BD : DD->bindings()) { - if (BD->isReferenced() || BD->hasAttr<UnusedAttr>()) + if (BD->isReferenced()) return false; - IsAllPlaceholders = IsAllPlaceholders && BD->isPlaceholderVar(LangOpts); + IsAllIgnored = IsAllIgnored && (BD->isPlaceholderVar(LangOpts) || + BD->hasAttr<UnusedAttr>()); } - if (IsAllPlaceholders) + if (IsAllIgnored) return false; } else if (!D->getDeclName()) { return false; diff --git a/clang/test/SemaCXX/unused-bindings.cpp b/clang/test/SemaCXX/unused-bindings.cpp new file mode 100644 index 0000000000000..83250dd4b0a11 --- /dev/null +++ b/clang/test/SemaCXX/unused-bindings.cpp @@ -0,0 +1,17 @@ +// RUN: %clang_cc1 -fsyntax-only -verify -std=c++26 -Wunused %s + +namespace GH125810 { +struct S { + int a, b; +}; + +void t(S s) { + auto &[_, _] = s; + auto &[a1, _] = s; // expected-warning {{unused variable '[a1, _]'}} + auto &[_, b2] = s; // expected-warning {{unused variable '[_, b2]'}} + + auto &[a3 [[maybe_unused]], b3 [[maybe_unused]]] = s; + auto &[a4, b4 [[maybe_unused]]] = s; // expected-warning {{unused variable '[a4, b4]'}} + auto &[a5 [[maybe_unused]], b5] = s; // expected-warning {{unused variable '[a5, b5]'}} +} +} diff --git a/clang/test/SemaCXX/unused.cpp b/clang/test/SemaCXX/unused.cpp index 1f40c1b1ca903..ab728069f2faf 100644 --- a/clang/test/SemaCXX/unused.cpp +++ b/clang/test/SemaCXX/unused.cpp @@ -114,7 +114,8 @@ namespace maybe_unused_binding { void test() { struct X { int a, b; } x; - auto [a [[maybe_unused]], b] = x; // expected-warning {{an attribute specifier sequence attached to a structured binding declaration is a C++2c extension}} + auto [a [[maybe_unused]], b] = x; // expected-warning {{an attribute specifier sequence attached to a structured binding declaration is a C++2c extension}} \ + // expected-warning {{unused variable '[a, b]'}} } } _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
