probinson added a subscriber: rsmith.
probinson added a comment.
In D69393#1729772 <https://reviews.llvm.org/D69393#1729772>, @yonghong-song
wrote:
> During experimenting with linux kernel codes, I found that clang does not
> allow address_space attribute for function pointers, specifically, in
> `clang/lib/Sema/SemaType.cpp`,
>
> // ISO/IEC TR 18037 S5.3 (amending C99 6.7.3): "A function type shall not be
> // qualified by an address-space qualifier."
> if (Type->isFunctionType()) {
> S.Diag(Attr.getLoc(), diag::err_attribute_address_function_type);
> Attr.setInvalid();
> return;
> }
>
>
> But linux kernel tries to annotate signal handling function pointer with
> address space to indicate it is accessing user space.
>
> typedef __signalfn_t __user *__sighandler_t;
> typedef __restorefn_t __user *__sigrestore_t;
>
>
> Such attribute makes sense for linux since indeed the signal handler code
> resides in user space and the kernel pointer
> merely points to user memory here.
>
> But such attributes are not allowed for function pointers.
>
> Maybe somebody can give some context about this particular ISO/IEC TR 18037
> specification? cc @probinson
I have no insight into the standards committees. @rsmith is your guru here.
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