bwendling wrote:
> So, we would actually get gcc's behavior with this patch:
>
> ```
> diff --git a/clang/lib/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp
> index c864714182e0..21ffe7b46a6e 100644
> --- a/clang/lib/CodeGen/CGBuiltin.cpp
> +++ b/clang/lib/CodeGen/CGBuiltin.cpp
> @@ -1049,25 +1049,7 @@ CodeGenFunction::emitFlexibleArrayMemberSize(const
> Expr *E, unsigned Type,
> Value *Res = FAMSize;
>
> if (isa<DeclRefExpr>(Base)) {
> - // The whole struct is specificed in the __bdos.
> - const ASTRecordLayout &Layout = Ctx.getASTRecordLayout(OuterRD);
> -
> - // Get the offset of the FAM.
> - llvm::Constant *FAMOffset = ConstantInt::get(ResType, Offset, IsSigned);
> - Value *OffsetAndFAMSize =
> - Builder.CreateAdd(FAMOffset, Res, "", !IsSigned, IsSigned);
> -
> - // Get the full size of the struct.
> - llvm::Constant *SizeofStruct =
> - ConstantInt::get(ResType, Layout.getSize().getQuantity(), IsSigned);
> -
> - // max(sizeof(struct s),
> - // offsetof(struct s, array) + p->count * sizeof(*p->array))
> - Res = IsSigned
> - ? Builder.CreateBinaryIntrinsic(llvm::Intrinsic::smax,
> - OffsetAndFAMSize, SizeofStruct)
> - : Builder.CreateBinaryIntrinsic(llvm::Intrinsic::umax,
> - OffsetAndFAMSize,
> SizeofStruct);
> + return nullptr;
> }
>
> // A negative \p IdxInst or \p CountedByInst means that the index lands
> ```
This just turns off `__builtin_dynamic_object_size(ptr, 0)`, which I'm not in
favor of.
https://github.com/llvm/llvm-project/pull/111015
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