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[Clang] Do not emit nodiscard warnings for the base expr of static member access (#131450)

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For an expression `nodiscard_function().static_member(), the nodiscard
warnings added by #120223, are not useful or actionable, and are
disruptive to some library implementations; we just remove them.

Fixes #131410
This commit is contained in:
cor3ntin 2025-03-15 22:27:08 +01:00 committed by GitHub
parent aadfa9f6c8
commit 9a1e39062b
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GPG Key ID: B5690EEEBB952194
5 changed files with 7 additions and 15 deletions
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5
clang/include/clang/Sema/Sema.h
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@ -10755,11 +10755,6 @@ public:
SourceLocation EndLoc);
void ActOnForEachDeclStmt(DeclGroupPtrTy Decl);
/// DiagnoseDiscardedExprMarkedNodiscard - Given an expression that is
/// semantically a discarded-value expression, diagnose if any [[nodiscard]]
/// value has been discarded.
void DiagnoseDiscardedExprMarkedNodiscard(const Expr *E);
/// DiagnoseUnusedExprResult - If the statement passed in is an expression
/// whose result is unused, warn.
void DiagnoseUnusedExprResult(const Stmt *S, unsigned DiagID);

1
clang/lib/Sema/SemaExprMember.cpp
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@ -1136,7 +1136,6 @@ Sema::BuildMemberReferenceExpr(Expr *BaseExpr, QualType BaseExprType,
if (Converted.isInvalid())
return true;
BaseExpr = Converted.get();
DiagnoseDiscardedExprMarkedNodiscard(BaseExpr);
return false;
};
auto ConvertBaseExprToGLValue = [&] {

4
clang/lib/Sema/SemaStmt.cpp
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@ -413,10 +413,6 @@ void DiagnoseUnused(Sema &S, const Expr *E, std::optional<unsigned> DiagID) {
}
} // namespace
void Sema::DiagnoseDiscardedExprMarkedNodiscard(const Expr *E) {
DiagnoseUnused(*this, E, std::nullopt);
}
void Sema::DiagnoseUnusedExprResult(const Stmt *S, unsigned DiagID) {
if (const LabelStmt *Label = dyn_cast_if_present<LabelStmt>(S))
S = Label->getSubStmt();

10
clang/test/CXX/dcl.dcl/dcl.attr/dcl.attr.nodiscard/p2.cpp
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@ -164,19 +164,21 @@ struct X {
[[nodiscard]] X get_X();
// cxx11-warning@-1 {{use of the 'nodiscard' attribute is a C++17 extension}}
[[nodiscard]] X* get_Ptr();
// cxx11-warning@-1 {{use of the 'nodiscard' attribute is a C++17 extension}}
void f() {
get_X(); // expected-warning{{ignoring return value of function declared with 'nodiscard' attribute}}
(void) get_X();
(void) get_X().variant_member;
(void) get_X().anonymous_struct_member;
(void) get_X().data_member;
(void) get_X().static_data_member;
// expected-warning@-1 {{ignoring return value of function declared with 'nodiscard' attribute}}
(void) get_X().unscoped_enum;
// expected-warning@-1 {{ignoring return value of function declared with 'nodiscard' attribute}}
(void) get_X().scoped_enum;
// expected-warning@-1 {{ignoring return value of function declared with 'nodiscard' attribute}}
(void) get_X().implicit_object_member_function();
(void) get_X().static_member_function();
// expected-warning@-1 {{ignoring return value of function declared with 'nodiscard' attribute}}
(void) get_Ptr()->implicit_object_member_function();
(void) get_Ptr()->static_member_function();
#if __cplusplus >= 202302L
(void) get_X().explicit_object_member_function();
#endif

2
clang/test/SemaCXX/ms-property.cpp
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@ -2,6 +2,7 @@
// RUN: %clang_cc1 -triple=x86_64-pc-win32 -fms-compatibility -emit-pch -o %t -verify %s
// RUN: %clang_cc1 -triple=x86_64-pc-win32 -fms-compatibility -include-pch %t %s -ast-print -o - | FileCheck %s
// RUN: %clang_cc1 -fdeclspec -fsyntax-only -verify %s -std=c++23
// expected-no-diagnostics
#ifndef HEADER
#define HEADER
@ -103,7 +104,6 @@ struct X {
void f() {
(void) get_x().imp;
(void) get_x().st;
// expected-warning@-1 {{ignoring return value of function declared with 'nodiscard' attribute}}
#if __cplusplus >= 202302L
(void) get_x().exp;
#endif