Author: Richard Smith Date: 2022-06-29T13:08:40-07:00 New Revision: dcea10c3c6ac963387e53f918c3616b64cb82e8d
URL: https://github.com/llvm/llvm-project/commit/dcea10c3c6ac963387e53f918c3616b64cb82e8d DIFF: https://github.com/llvm/llvm-project/commit/dcea10c3c6ac963387e53f918c3616b64cb82e8d.diff LOG: Fix miscompile with [[no_unique_address]] struct fields. If a zero-sized field has a non-trivial initializer, it should prevent the overall struct initialization from being folded to a constant during IR generation. Don't just ignore zero-sized fields entirely in IR constant emission. Added: Modified: clang/lib/CodeGen/CGExprConstant.cpp clang/test/CodeGenCXX/no-unique-address.cpp Removed: ################################################################################ diff --git a/clang/lib/CodeGen/CGExprConstant.cpp b/clang/lib/CodeGen/CGExprConstant.cpp index 91fdb88d6bb7a..b83a874432508 100644 --- a/clang/lib/CodeGen/CGExprConstant.cpp +++ b/clang/lib/CodeGen/CGExprConstant.cpp @@ -703,8 +703,8 @@ bool ConstStructBuilder::Build(InitListExpr *ILE, bool AllowOverwrite) { !declaresSameEntity(ILE->getInitializedFieldInUnion(), Field)) continue; - // Don't emit anonymous bitfields or zero-sized fields. - if (Field->isUnnamedBitfield() || Field->isZeroSize(CGM.getContext())) + // Don't emit anonymous bitfields. + if (Field->isUnnamedBitfield()) continue; // Get the initializer. A struct can include fields without initializers, @@ -715,6 +715,14 @@ bool ConstStructBuilder::Build(InitListExpr *ILE, bool AllowOverwrite) { if (Init && isa<NoInitExpr>(Init)) continue; + // Zero-sized fields are not emitted, but their initializers may still + // prevent emission of this struct as a constant. + if (Field->isZeroSize(CGM.getContext())) { + if (Init->HasSideEffects(CGM.getContext())) + return false; + continue; + } + // When emitting a DesignatedInitUpdateExpr, a nested InitListExpr // represents additional overwriting of our current constant value, and not // a new constant to emit independently. diff --git a/clang/test/CodeGenCXX/no-unique-address.cpp b/clang/test/CodeGenCXX/no-unique-address.cpp index 8ecbd69aa54bb..c0678aca5b0c8 100644 --- a/clang/test/CodeGenCXX/no-unique-address.cpp +++ b/clang/test/CodeGenCXX/no-unique-address.cpp @@ -93,3 +93,14 @@ int loadWhereLaterDeclaredFieldHasLowerOffset(LaterDeclaredFieldHasLowerOffset & // Note, never emit TBAA for zero-size fields. // CHECK-OPT: ![[TBAA_AB]] = !{![[TBAA_A:[0-9]*]], ![[TBAA_INT:[0-9]*]], i64 4} // CHECK-OPT: ![[TBAA_A]] = !{!"_ZTS32LaterDeclaredFieldHasLowerOffset", ![[TBAA_INT]], i64 0, ![[TBAA_INT]], i64 4} + +struct NonTrivialInit { + NonTrivialInit(); +}; +struct HasZeroSizedFieldWithNonTrivialInit { + int a; + [[no_unique_address]] NonTrivialInit b; +}; +HasZeroSizedFieldWithNonTrivialInit testHasZeroSizedFieldWithNonTrivialInit = {.a = 1}; +// CHECK-LABEL: define {{.*}}cxx_global_var_init +// CHECK: call {{.*}}@_ZN14NonTrivialInitC1Ev({{.*}}@testHasZeroSizedFieldWithNonTrivialInit _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
