https://github.com/tbaederr updated https://github.com/llvm/llvm-project/pull/192212
>From eb7e034c9e83e6646f916eacac0d3641524d0a5f Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Timm=20B=C3=A4der?= <[email protected]> Date: Wed, 15 Apr 2026 10:52:42 +0200 Subject: [PATCH] [clang][bytecode] Don't implicitly begin union member lifetime... ... on assignment operator calls if the LHS type does not have a non-deleted trivial default constructor. --- clang/lib/AST/ByteCode/Compiler.cpp | 5 ++++- clang/test/AST/ByteCode/unions.cpp | 23 +++++++++++++++++++++++ 2 files changed, 27 insertions(+), 1 deletion(-) diff --git a/clang/lib/AST/ByteCode/Compiler.cpp b/clang/lib/AST/ByteCode/Compiler.cpp index 59510612d9617..f131b9eab3cbf 100644 --- a/clang/lib/AST/ByteCode/Compiler.cpp +++ b/clang/lib/AST/ByteCode/Compiler.cpp @@ -5601,6 +5601,7 @@ bool Compiler<Emitter>::VisitCallExpr(const CallExpr *E) { SmallVector<const Expr *, 8> Args(ArrayRef(E->getArgs(), E->getNumArgs())); bool IsAssignmentOperatorCall = false; + bool ActivateLHS = false; if (const auto *OCE = dyn_cast<CXXOperatorCallExpr>(E); OCE && OCE->isAssignmentOp()) { // Just like with regular assignments, we need to special-case assignment @@ -5609,6 +5610,8 @@ bool Compiler<Emitter>::VisitCallExpr(const CallExpr *E) { assert(Args.size() == 2); IsAssignmentOperatorCall = true; std::reverse(Args.begin(), Args.end()); + const CXXRecordDecl *LHSRecord = Args[0]->getType()->getAsCXXRecordDecl(); + ActivateLHS = !LHSRecord || LHSRecord->hasTrivialDefaultConstructor(); } // Calling a static operator will still // pass the instance, but we don't need it. @@ -5684,7 +5687,7 @@ bool Compiler<Emitter>::VisitCallExpr(const CallExpr *E) { return false; } - if (!this->visitCallArgs(Args, FuncDecl, IsAssignmentOperatorCall, + if (!this->visitCallArgs(Args, FuncDecl, ActivateLHS, isa<CXXOperatorCallExpr>(E))) return false; diff --git a/clang/test/AST/ByteCode/unions.cpp b/clang/test/AST/ByteCode/unions.cpp index 2123a932fce10..2422b76a8bd6e 100644 --- a/clang/test/AST/ByteCode/unions.cpp +++ b/clang/test/AST/ByteCode/unions.cpp @@ -1007,4 +1007,27 @@ namespace NonTrivialUnionCtor { static_assert(j()); // both-error {{not an integral constant expression}} \ // both-note {{in call to}} } + +/// u.a should not implicitly get activated when assigning to it, since A +/// does not have a non-deleted trivial default constructor. +namespace NoTrivialCtor { + struct A { + int i; + constexpr A() : i(0) {} + constexpr A(int i) : i(i) {} + }; + + constexpr auto test() { + union U { + int i; + A a; + } u{.i = 0}; + + u.a = {123}; // both-note {{member call on member 'a' of union with active member 'i'}} + return u.a.i; + } + + constexpr auto r = test(); // both-error {{must be initialized by a constant expression}} \ + // both-note {{in call to}} +} #endif _______________________________________________ cfe-commits mailing list [email protected] https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
