llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT--> @llvm/pr-subscribers-clang Author: Doug Wyatt (dougsonos) <details> <summary>Changes</summary> The current function effect diagnostics include these behaviors: When you declare a function `nonblocking` (typically in a header) and then omit the attribute on the implementation (or any other redeclaration), Clang warns: attribute 'nonblocking' on function does not match previous declaration. But if a `nonblocking` function is a C++ virtual method, then overrides are implicitly nonblocking; the attribute doesn't need to be explicitly stated. These behaviors are arguably inconsistent -- and also, both, more pedantic than the rest of the function effect diagnostics. This PR accomplishes two things: - Separates the diagnostic on a redeclaration into a new group, `-Wfunction-effect-redeclarations`, so it can be disabled independently. - Adds a second diagnostic to this new group, for the case of an override method missing the attribute. (This helps in a situation where I'm trying to add `nonblocking` via a macro that does other things and I want to know that the macro is missing on an override declaration.) --- Full diff: https://github.com/llvm/llvm-project/pull/148690.diff 4 Files Affected: - (modified) clang/include/clang/Basic/DiagnosticGroups.td (+1) - (modified) clang/include/clang/Basic/DiagnosticSemaKinds.td (+10-5) - (modified) clang/lib/Sema/SemaDeclCXX.cpp (+9-1) - (modified) clang/test/Sema/attr-nonblocking-sema.cpp (+7-7) ``````````diff diff --git a/clang/include/clang/Basic/DiagnosticGroups.td b/clang/include/clang/Basic/DiagnosticGroups.td index 9a7a308600763..b59439d26a71a 100644 --- a/clang/include/clang/Basic/DiagnosticGroups.td +++ b/clang/include/clang/Basic/DiagnosticGroups.td @@ -1291,6 +1291,7 @@ def ThreadSafetyBeta : DiagGroup<"thread-safety-beta">; // Warnings and notes related to the function effects system which underlies // the nonblocking and nonallocating attributes. def FunctionEffects : DiagGroup<"function-effects">; +def FunctionEffectRedeclarations : DiagGroup<"function-effect-redeclarations">; def PerfConstraintImpliesNoexcept : DiagGroup<"perf-constraint-implies-noexcept">; // Uniqueness Analysis warnings diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td index 577adc30ba2fa..2b1fa4330d325 100644 --- a/clang/include/clang/Basic/DiagnosticSemaKinds.td +++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td @@ -11529,17 +11529,22 @@ def note_in_evaluating_default_argument : Note< def warn_invalid_add_func_effects : Warning< "attribute '%0' should not be added via type conversion">, InGroup<FunctionEffects>, DefaultIgnore; -def warn_mismatched_func_effect_override : Warning< - "attribute '%0' on overriding function does not match base declaration">, - InGroup<FunctionEffects>, DefaultIgnore; -def warn_mismatched_func_effect_redeclaration : Warning< - "attribute '%0' on function does not match previous declaration">, +def warn_conflicting_func_effect_override : Warning< + "attribute '%0' on overriding function conflicts with base declaration">, InGroup<FunctionEffects>, DefaultIgnore; def warn_conflicting_func_effects : Warning< "effects conflict when merging declarations; kept '%0', discarded '%1'">, InGroup<FunctionEffects>, DefaultIgnore; def err_func_with_effects_no_prototype : Error< "'%0' function must have a prototype">; +// These are more pedantic: in redeclarations and virtual method overrides, +// the effect attribute(s) should be restated. +def warn_mismatched_func_effect_override : Warning< + "overriding function is missing '%0' attribute from base declaration">, + InGroup<FunctionEffectRedeclarations>, DefaultIgnore; +def warn_mismatched_func_effect_redeclaration : Warning< + "redeclaration is missing '%0' attribute from previous declaration">, + InGroup<FunctionEffectRedeclarations>, DefaultIgnore; } // end of sema category diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp index 5cc92ebb0171f..090a1d9d290bb 100644 --- a/clang/lib/Sema/SemaDeclCXX.cpp +++ b/clang/lib/Sema/SemaDeclCXX.cpp @@ -18686,7 +18686,7 @@ bool Sema::CheckOverridingFunctionAttributes(CXXMethodDecl *New, case FunctionEffectDiff::OverrideResult::NoAction: break; case FunctionEffectDiff::OverrideResult::Warn: - Diag(New->getLocation(), diag::warn_mismatched_func_effect_override) + Diag(New->getLocation(), diag::warn_conflicting_func_effect_override) << Diff.effectName(); Diag(Old->getLocation(), diag::note_overridden_virtual_function) << Old->getReturnTypeSourceRange(); @@ -18699,6 +18699,14 @@ bool Sema::CheckOverridingFunctionAttributes(CXXMethodDecl *New, QualType ModQT = Context.getFunctionType(NewFT->getReturnType(), NewFT->getParamTypes(), EPI); New->setType(ModQT); + if (Errs.empty()) { + // A warning here is somewhat pedantic, in a different warning group. + // Skip this if there was already a merge conflict, which is more serious. + Diag(New->getLocation(), diag::warn_mismatched_func_effect_override) + << Diff.effectName(); + Diag(Old->getLocation(), diag::note_overridden_virtual_function) + << Old->getReturnTypeSourceRange(); + } break; } } diff --git a/clang/test/Sema/attr-nonblocking-sema.cpp b/clang/test/Sema/attr-nonblocking-sema.cpp index f13cc783dfc33..b8a9071aae50c 100644 --- a/clang/test/Sema/attr-nonblocking-sema.cpp +++ b/clang/test/Sema/attr-nonblocking-sema.cpp @@ -1,5 +1,5 @@ -// RUN: %clang_cc1 -fsyntax-only -fblocks -fcxx-exceptions -verify -Wfunction-effects %s -// RUN: %clang_cc1 -fsyntax-only -fblocks -verify -x c -std=c23 -Wfunction-effects %s +// RUN: %clang_cc1 -fsyntax-only -fblocks -fcxx-exceptions -verify -Wfunction-effects -Wfunction-effect-redeclarations %s +// RUN: %clang_cc1 -fsyntax-only -fblocks -verify -x c -std=c23 -Wfunction-effects -Wfunction-effect-redeclarations %s #if !__has_attribute(nonblocking) #error "the 'nonblocking' attribute is not available" @@ -132,15 +132,15 @@ void type_conversions_2() #ifdef __cplusplus struct Base { virtual void f1(); - virtual void nonblocking() noexcept [[clang::nonblocking]]; - virtual void nonallocating() noexcept [[clang::nonallocating]]; + virtual void nonblocking() noexcept [[clang::nonblocking]]; // expected-note {{overridden virtual function is here}} + virtual void nonallocating() noexcept [[clang::nonallocating]]; // expected-note {{overridden virtual function is here}} virtual void f2() [[clang::nonallocating]]; // expected-note {{previous declaration is here}} }; struct Derived : public Base { void f1() [[clang::nonblocking]] override; - void nonblocking() noexcept override; - void nonallocating() noexcept override; + void nonblocking() noexcept override; // expected-warning {{overriding function is missing 'nonblocking' attribute from base declaration}} + void nonallocating() noexcept override; // expected-warning {{overriding function is missing 'nonallocating' attribute from base declaration}} void f2() [[clang::allocating]] override; // expected-warning {{effects conflict when merging declarations; kept 'allocating', discarded 'nonallocating'}} }; #endif // __cplusplus @@ -149,7 +149,7 @@ struct Derived : public Base { void f2(); void f2() [[clang::nonblocking]]; // expected-note {{previous declaration is here}} -void f2(); // expected-warning {{attribute 'nonblocking' on function does not match previous declaration}} +void f2(); // expected-warning {{redeclaration is missing 'nonblocking' attribute from previous declaration}} // Note: we verify that the attribute is actually seen during the constraints tests. void f3() [[clang::blocking]]; // expected-note {{previous declaration is here}} `````````` </details> https://github.com/llvm/llvm-project/pull/148690 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
