https://github.com/yuxuanchen1997 created https://github.com/llvm/llvm-project/pull/70973
This PR is proposing a fix for https://github.com/llvm/llvm-project/issues/65971. Previously, given a coroutine like this ``` task foo(int a) { co_return; } ``` Parameter `a` is never used. However, because C++ coroutines move constructs the variable to a heap allocated coroutine activation frame, we considered all parameters referenced. When diagnosing unused parameters, we cannot distinguish if the variable reference was due to coroutine parameter moves. Compiler Explorer shows that GCC warns against this case correctly, but clang does not: https://godbolt.org/z/Wo7dfqeaf This patch addresses this issue by preserving the original `ParmVarDecl`'s `Referenced` state. >From 54255c560c01a1fd017c52898b8688e24c4397e5 Mon Sep 17 00:00:00 2001 From: Yuxuan Chen <y...@meta.com> Date: Wed, 1 Nov 2023 11:59:57 -0700 Subject: [PATCH] [Clang] Preserve coroutine parameter referenced state --- clang/lib/Sema/SemaCoroutine.cpp | 6 ++++ .../warn-unused-parameters-coroutine.cpp | 28 +++++++++++++++++++ 2 files changed, 34 insertions(+) create mode 100644 clang/test/SemaCXX/warn-unused-parameters-coroutine.cpp diff --git a/clang/lib/Sema/SemaCoroutine.cpp b/clang/lib/Sema/SemaCoroutine.cpp index 38ac406b14adadf..281b7d68d361fcc 100644 --- a/clang/lib/Sema/SemaCoroutine.cpp +++ b/clang/lib/Sema/SemaCoroutine.cpp @@ -1965,9 +1965,15 @@ bool Sema::buildCoroutineParameterMoves(SourceLocation Loc) { if (PD->getType()->isDependentType()) continue; + // Preserve the referenced state of the parameters for diagnosis purposes. + bool DeclReferenced = PD->isReferenced(); + ExprResult PDRefExpr = BuildDeclRefExpr(PD, PD->getType().getNonReferenceType(), ExprValueKind::VK_LValue, Loc); // FIXME: scope? + + PD->setReferenced(DeclReferenced); + if (PDRefExpr.isInvalid()) return false; diff --git a/clang/test/SemaCXX/warn-unused-parameters-coroutine.cpp b/clang/test/SemaCXX/warn-unused-parameters-coroutine.cpp new file mode 100644 index 000000000000000..0fd26ea4a21be79 --- /dev/null +++ b/clang/test/SemaCXX/warn-unused-parameters-coroutine.cpp @@ -0,0 +1,28 @@ +// RUN: %clang_cc1 -fsyntax-only -Wunused-parameter -verify -std=c++20 %s + +#include "Inputs/std-coroutine.h" + +struct awaitable { + bool await_ready() noexcept; + void await_resume() noexcept; + void await_suspend(std::coroutine_handle<>) noexcept; +}; + +struct task : awaitable { + struct promise_type { + task get_return_object() noexcept; + awaitable initial_suspend() noexcept; + awaitable final_suspend() noexcept; + void unhandled_exception() noexcept; + void return_void() noexcept; + }; +}; + +task foo(int a) { // expected-warning{{unused parameter 'a'}} + co_return; +} + +task bar(int a, int b) { // expected-warning{{unused parameter 'b'}} + a = a + 1; + co_return; +} _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
