Author: Hana Dusíková Date: 2021-04-13T15:45:09-04:00 New Revision: 64c24f493e5f4637ee193f10f469cdd2695b4ba6
URL: https://github.com/llvm/llvm-project/commit/64c24f493e5f4637ee193f10f469cdd2695b4ba6 DIFF: https://github.com/llvm/llvm-project/commit/64c24f493e5f4637ee193f10f469cdd2695b4ba6.diff LOG: Remove warning "suggest braces" for aggregate initialization of an empty class with an aggregate base class. I recently ran into issues with aggregates and inheritance, I'm using it for creating a type-safe library where most of the types are build over "tagged" std::array. After bit of cleaning and enabling -Wall -Wextra -pedantic I noticed clang only in my pipeline gives me warning. After a bit of focusing on it I found it's not helpful, and contemplate disabling the warning all together. After a discussion with other library authors I found it's bothering more people and decided to fix it. Removes this warning: template<typename T, int N> struct StdArray { T contents[N]; }; template<typename T, int N> struct AggregateAndEmpty : StdArray<T,N> { }; AggregateAndEmpty<int, 3> p = {1, 2, 3}; // <-- warning here about omitted braces Added: Modified: clang/lib/Sema/SemaInit.cpp clang/test/SemaCXX/aggregate-initialization.cpp Removed: ################################################################################ diff --git a/clang/lib/Sema/SemaInit.cpp b/clang/lib/Sema/SemaInit.cpp index ec7e4722ea4e..c8e8c8696b6a 100644 --- a/clang/lib/Sema/SemaInit.cpp +++ b/clang/lib/Sema/SemaInit.cpp @@ -1007,21 +1007,33 @@ static bool isIdiomaticBraceElisionEntity(const InitializedEntity &Entity) { // // (where std::array is an aggregate struct containing a single array field. - // FIXME: Should aggregate initialization of a struct with a single - // base class and no members also suppress the warning? - if (Entity.getKind() != InitializedEntity::EK_Member || !Entity.getParent()) + if (!Entity.getParent()) return false; - auto *ParentRD = - Entity.getParent()->getType()->castAs<RecordType>()->getDecl(); - if (CXXRecordDecl *CXXRD = dyn_cast<CXXRecordDecl>(ParentRD)) - if (CXXRD->getNumBases()) - return false; + // Allows elide brace initialization for aggregates with empty base. + if (Entity.getKind() == InitializedEntity::EK_Base) { + auto *ParentRD = + Entity.getParent()->getType()->castAs<RecordType>()->getDecl(); + CXXRecordDecl *CXXRD = cast<CXXRecordDecl>(ParentRD); + return CXXRD->getNumBases() == 1 && CXXRD->field_empty(); + } + + // Allow brace elision if the only subobject is a field. + if (Entity.getKind() == InitializedEntity::EK_Member) { + auto *ParentRD = + Entity.getParent()->getType()->castAs<RecordType>()->getDecl(); + if (CXXRecordDecl *CXXRD = dyn_cast<CXXRecordDecl>(ParentRD)) { + if (CXXRD->getNumBases()) { + return false; + } + } + auto FieldIt = ParentRD->field_begin(); + assert(FieldIt != ParentRD->field_end() && + "no fields but have initializer for member?"); + return ++FieldIt == ParentRD->field_end(); + } - auto FieldIt = ParentRD->field_begin(); - assert(FieldIt != ParentRD->field_end() && - "no fields but have initializer for member?"); - return ++FieldIt == ParentRD->field_end(); + return false; } /// Check whether the range of the initializer \p ParentIList from element diff --git a/clang/test/SemaCXX/aggregate-initialization.cpp b/clang/test/SemaCXX/aggregate-initialization.cpp index c71a7449d31d..3c12aca12d21 100644 --- a/clang/test/SemaCXX/aggregate-initialization.cpp +++ b/clang/test/SemaCXX/aggregate-initialization.cpp @@ -172,11 +172,20 @@ namespace IdiomaticStdArrayInitDoesNotWarn { }; ArrayAndBaseClass<int, 3> z = {1, 2, 3}; // expected-warning {{suggest braces}} - // It's not clear whether we should be warning in this case. If this - // pattern becomes idiomatic, it would be reasonable to suppress the - // warning here too. + // This pattern is used for tagged aggregates and must not warn template<typename T, int N> struct JustABaseClass : StdArray<T, N> {}; - JustABaseClass<int, 3> w = {1, 2, 3}; // expected-warning {{suggest braces}} + JustABaseClass<int, 3> w = {1, 2, 3}; + // but this should be also ok + JustABaseClass<int, 3> v = {{1, 2, 3}}; + + template <typename T, int N> struct OnionBaseClass : JustABaseClass<T, N> {}; + OnionBaseClass<int, 3> u = {1, 2, 3}; + OnionBaseClass<int, 3> t = {{{1, 2, 3}}}; + + struct EmptyBase {}; + + template <typename T, int N> struct AggregateAndEmpty : StdArray<T, N>, EmptyBase {}; + AggregateAndEmpty<int, 3> p = {1, 2, 3}; // expected-warning {{suggest braces}} #endif #pragma clang diagnostic pop _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
