Author: Timm Baeder Date: 2025-02-25T12:46:06+01:00 New Revision: dff2ca424c20c672b418ec86ac3a120fad4fb364
URL: https://github.com/llvm/llvm-project/commit/dff2ca424c20c672b418ec86ac3a120fad4fb364 DIFF: https://github.com/llvm/llvm-project/commit/dff2ca424c20c672b418ec86ac3a120fad4fb364.diff LOG: [clang][bytecode] Add special case for anonymous unions (#128681) This fixes the expected output to match the one of the current interpreter. Added: Modified: clang/lib/AST/ByteCode/Interp.cpp clang/lib/AST/ByteCode/Pointer.cpp clang/lib/AST/ByteCode/Pointer.h clang/test/AST/ByteCode/unions.cpp Removed: ################################################################################ diff --git a/clang/lib/AST/ByteCode/Interp.cpp b/clang/lib/AST/ByteCode/Interp.cpp index 31126e48c7cd7..5e0d2e91fb1b2 100644 --- a/clang/lib/AST/ByteCode/Interp.cpp +++ b/clang/lib/AST/ByteCode/Interp.cpp @@ -139,17 +139,19 @@ static bool CheckActive(InterpState &S, CodePtr OpPC, const Pointer &Ptr, Pointer U = Ptr.getBase(); Pointer C = Ptr; - while (!U.isRoot() && U.inUnion() && !U.isActive()) { - if (U.getField()) - C = U; + while (!U.isRoot() && !U.isActive()) { + // A little arbitrary, but this is what the current interpreter does. + // See the AnonymousUnion test in test/AST/ByteCode/unions.cpp. + // GCC's output is more similar to what we would get without + // this condition. + if (U.getRecord() && U.getRecord()->isAnonymousUnion()) + break; + + C = U; U = U.getBase(); } assert(C.isField()); - // Get the inactive field descriptor. - const FieldDecl *InactiveField = C.getField(); - assert(InactiveField); - // Consider: // union U { // struct { @@ -165,6 +167,11 @@ static bool CheckActive(InterpState &S, CodePtr OpPC, const Pointer &Ptr, if (!U.getFieldDesc()->isUnion()) return true; + // Get the inactive field descriptor. + assert(!C.isActive()); + const FieldDecl *InactiveField = C.getField(); + assert(InactiveField); + // Find the active field of the union. const Record *R = U.getRecord(); assert(R && R->isUnion() && "Not a union"); diff --git a/clang/lib/AST/ByteCode/Pointer.cpp b/clang/lib/AST/ByteCode/Pointer.cpp index 3033bd47adf75..92cfa192fd385 100644 --- a/clang/lib/AST/ByteCode/Pointer.cpp +++ b/clang/lib/AST/ByteCode/Pointer.cpp @@ -437,28 +437,35 @@ void Pointer::activate() const { if (!getInlineDesc()->InUnion) return; - getInlineDesc()->IsActive = true; + auto activate = [](Pointer &P) -> void { + P.getInlineDesc()->IsActive = true; + }; + auto deactivate = [](Pointer &P) -> void { + P.getInlineDesc()->IsActive = false; + }; - // Get the union, iterate over its fields and DEactivate all others. + // Unions might be nested etc., so find the topmost Pointer that's + // not in a union anymore. Pointer UnionPtr = getBase(); - while (!UnionPtr.getFieldDesc()->isUnion()) + while (!UnionPtr.isRoot() && UnionPtr.inUnion()) UnionPtr = UnionPtr.getBase(); + assert(UnionPtr.getFieldDesc()->isUnion()); + const Record *UnionRecord = UnionPtr.getRecord(); for (const Record::Field &F : UnionRecord->fields()) { Pointer FieldPtr = UnionPtr.atField(F.Offset); if (FieldPtr == *this) { } else { - FieldPtr.getInlineDesc()->IsActive = false; + deactivate(FieldPtr); // FIXME: Recurse. } } - Pointer B = getBase(); - while (!B.isRoot() && B.inUnion()) { + Pointer B = *this; + while (B != UnionPtr) { + activate(B); // FIXME: Need to de-activate other fields of parent records. - B.getInlineDesc()->IsActive = true; - assert(B.isActive()); B = B.getBase(); } } diff --git a/clang/lib/AST/ByteCode/Pointer.h b/clang/lib/AST/ByteCode/Pointer.h index 3970d5833fcdc..fd33ee9955f55 100644 --- a/clang/lib/AST/ByteCode/Pointer.h +++ b/clang/lib/AST/ByteCode/Pointer.h @@ -494,9 +494,6 @@ class Pointer { /// Returns the field information. const FieldDecl *getField() const { return getFieldDesc()->asFieldDecl(); } - /// Checks if the object is a union. - bool isUnion() const; - /// Checks if the storage is extern. bool isExtern() const { if (isBlockPointer()) diff --git a/clang/test/AST/ByteCode/unions.cpp b/clang/test/AST/ByteCode/unions.cpp index c6b5e34810f05..2064cae11e970 100644 --- a/clang/test/AST/ByteCode/unions.cpp +++ b/clang/test/AST/ByteCode/unions.cpp @@ -485,4 +485,23 @@ namespace IFD { } static_assert(test()); } + +namespace AnonymousUnion { + struct A { + int x; + union { int p, q; }; + }; + union B { + A a; + int bb; + }; + + constexpr B return_init_all() { + B b = {.bb = 1}; + b.a.x = 2; + return b; + } + static_assert(return_init_all().a.p == 7); // both-error {{}} \ + // both-note {{read of member 'p' of union with no active member}} +} #endif _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
