================
@@ -1060,238 +1061,348 @@
CodeGenFunction::evaluateOrEmitBuiltinObjectSize(const Expr *E, unsigned Type,
return ConstantInt::get(ResType, ObjectSize, /*isSigned=*/true);
}
-const FieldDecl *CodeGenFunction::FindFlexibleArrayMemberFieldAndOffset(
- ASTContext &Ctx, const RecordDecl *RD, const FieldDecl *FAMDecl,
- uint64_t &Offset) {
+namespace {
+
+/// StructFieldAccess is a simple visitor class to grab the first MemberExpr
+/// from an Expr. It records any ArraySubscriptExpr we meet along the way.
+struct StructFieldAccess
+ : public ConstStmtVisitor<StructFieldAccess, const MemberExpr *> {
+ const ArraySubscriptExpr *ASE = nullptr;
+ bool AddrOfSeen = false;
+
+ const MemberExpr *VisitMemberExpr(const MemberExpr *E) {
+ if (AddrOfSeen && E->getType()->isArrayType())
+ // Avoid forms like '&ptr->array'.
+ return nullptr;
+ return E;
+ }
+
+ const MemberExpr *VisitArraySubscriptExpr(const ArraySubscriptExpr *E) {
+ AddrOfSeen = false; // '&ptr->array[idx]' is okay.
+ ASE = E;
+ return Visit(E->getBase());
+ }
+ const MemberExpr *VisitCastExpr(const CastExpr *E) {
+ return Visit(E->getSubExpr());
+ }
+ const MemberExpr *VisitParenExpr(const ParenExpr *E) {
+ return Visit(E->getSubExpr());
+ }
+ const MemberExpr *VisitUnaryAddrOf(const clang::UnaryOperator *E) {
+ AddrOfSeen = true;
+ return Visit(E->getSubExpr());
+ }
+ const MemberExpr *VisitUnaryDeref(const clang::UnaryOperator *E) {
+ AddrOfSeen = false;
+ return Visit(E->getSubExpr());
+ }
+};
+
+} // end anonymous namespace
+
+/// Find a struct's flexible array member. It may be embedded inside multiple
+/// sub-structs, but must still be the last field.
+static const FieldDecl *FindFlexibleArrayMemberField(CodeGenFunction &CGF,
+ ASTContext &Ctx,
+ const RecordDecl *RD) {
const LangOptions::StrictFlexArraysLevelKind StrictFlexArraysLevel =
- getLangOpts().getStrictFlexArraysLevel();
- uint32_t FieldNo = 0;
+ CGF.getLangOpts().getStrictFlexArraysLevel();
if (RD->isImplicit())
return nullptr;
for (const FieldDecl *FD : RD->fields()) {
- if ((!FAMDecl || FD == FAMDecl) &&
- Decl::isFlexibleArrayMemberLike(
+ if (Decl::isFlexibleArrayMemberLike(
Ctx, FD, FD->getType(), StrictFlexArraysLevel,
- /*IgnoreTemplateOrMacroSubstitution=*/true)) {
- const ASTRecordLayout &Layout = Ctx.getASTRecordLayout(RD);
- Offset += Layout.getFieldOffset(FieldNo);
+ /*IgnoreTemplateOrMacroSubstitution=*/true))
return FD;
+
+ if (auto RT = FD->getType()->getAs<RecordType>())
+ if (const FieldDecl *FD =
+ FindFlexibleArrayMemberField(CGF, Ctx, RT->getAsRecordDecl()))
+ return FD;
+ }
+
+ return nullptr;
+}
+
+/// Calculate the offset of a struct field. It may be embedded inside multiple
+/// sub-structs.
+static bool GetFieldOffset(ASTContext &Ctx, const RecordDecl *RD,
+ const FieldDecl *FD, int64_t &Offset) {
+ if (RD->isImplicit())
+ return false;
+
+ const ASTRecordLayout &Layout = Ctx.getASTRecordLayout(RD);
+ uint32_t FieldNo = 0;
+
+ for (const FieldDecl *Field : RD->fields()) {
+ if (Field == FD) {
+ Offset += Layout.getFieldOffset(FieldNo);
+ return true;
}
- QualType Ty = FD->getType();
- if (Ty->isRecordType()) {
- if (const FieldDecl *Field = FindFlexibleArrayMemberFieldAndOffset(
- Ctx, Ty->getAsRecordDecl(), FAMDecl, Offset)) {
- const ASTRecordLayout &Layout = Ctx.getASTRecordLayout(RD);
+ if (auto RT = Field->getType()->getAs<RecordType>()) {
+ if (GetFieldOffset(Ctx, RT->getAsRecordDecl(), FD, Offset)) {
Offset += Layout.getFieldOffset(FieldNo);
- return Field;
+ return true;
}
}
if (!RD->isUnion())
++FieldNo;
}
- return nullptr;
+ return false;
}
-static unsigned CountCountedByAttrs(const RecordDecl *RD) {
- unsigned Num = 0;
+llvm::Value *
+CodeGenFunction::emitCountedByMemberSize(const Expr *E, llvm::Value *EmittedE,
+ unsigned Type,
+ llvm::IntegerType *ResType) {
+ ASTContext &Ctx = getContext();
- for (const FieldDecl *FD : RD->fields()) {
- if (FD->getType()->isCountAttributedType())
- return ++Num;
+ // Note: If the whole struct is specificed in the __bdos (i.e. Visitor
+ // returns a DeclRefExpr). The calculation of the whole size of the structure
+ // with a flexible array member can be done in two ways:
+ //
+ // 1) sizeof(struct S) + count * sizeof(typeof(fam))
+ // 2) offsetof(struct S, fam) + count * sizeof(typeof(fam))
+ //
+ // The first will add additional padding after the end of the array
+ // allocation while the second method is more precise, but not quite expected
+ // from programmers. See
+ // https://lore.kernel.org/lkml/ZvV6X5FPBBW7CO1f@archlinux/ for a discussion
+ // of the topic.
+ //
+ // GCC isn't (currently) able to calculate __bdos on a pointer to the whole
+ // structure. Therefore, because of the above issue, we choose to match what
+ // GCC does for consistency's sake.
----------------
nickdesaulniers wrote:
This seems to imply a bug in gcc. What if that changes in the future?
Is there a bug on file in their issue tracker you could link to from here? If
not, does it make sense to file one, then link to it from here?
https://github.com/llvm/llvm-project/pull/122198
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