[PATCH] D93630: [Attr] Apply GNU-style attributes to expression statements

[Aaron Ballman via Phabricator via cfe-commits]

aaron.ballman added a comment.

In D93630#2468241 <https://reviews.llvm.org/D93630#2468241>, @vsavchenko wrote:

> In D93630#2468197 <https://reviews.llvm.org/D93630#2468197>, @aaron.ballman wrote:
>
>> However, taking a step back -- what attributes would need this functionality (and couldn't be written on something within the expression statement)?
>
> It is still good old `suppress`, it is very counter-intuitive when you put `suppress` and it causes some weird parse errors: https://godbolt.org/z/zzY64q

Yeah, I kind of figured that might be the cause. I'm not 100% convinced (one way or the other) if the suppress attribute should get a GNU spelling. The `[[]]` spellings are available in all language modes (we have `-fdouble-square-bracket-attributes` to enable this) and don't run afoul of the "guess what this attribute appertains to" problem that GNU-style attributes do.



================
Comment at: clang/lib/Parse/ParseStmt.cpp:213
              ParsedStmtContext()) &&
-        (GNUAttributeLoc.isValid() || isDeclarationStatement())) {
+        ((GNUAttributeLoc.isValid() && !Attrs.back().isStmtAttr()) ||
+         isDeclarationStatement())) {
----------------
I think you need to ensure there's at least one attribute before checking `!Attrs.back().isStmtAttr()` as this may cause problems if the user does something odd like `__attribute__(()) int x;` (I don't know if this will result in a valid `GNUAttributeLoc` with no attributes or not.)

I'm not certain that logic is perfect either. It would be pretty mysterious to handle these cases differently:
```
__attribute__((stmt_attr, decl_attr)) int a, b, c;
__attribute__((decl_attr, stmt_attr)) int x, y, z;
```


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D93630/new/

https://reviews.llvm.org/D93630