[clang] Support [[guarded_by(mutex)]] attribute inside C struct (PR #94216)

[Dan Liew via cfe-commits]

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@@ -3330,6 +3340,112 @@ void Parser::DistributeCLateParsedAttrs(Decl *Dcl,
   }
 }
 
+/// GuardedBy attributes (e.g., guarded_by):
+///   AttrName '(' expression ')'
+void Parser::ParseGuardedByAttribute(
+    IdentifierInfo &AttrName, SourceLocation AttrNameLoc,
+    ParsedAttributes &Attrs, IdentifierInfo *ScopeName, SourceLocation ScopeLoc,
+    SourceLocation *EndLoc, ParsedAttr::Form Form) {
+  assert(Tok.is(tok::l_paren) && "Attribute arg list not starting with '('");
+
+  BalancedDelimiterTracker Parens(*this, tok::l_paren);
+  Parens.consumeOpen();
+
+  if (Tok.is(tok::r_paren)) {
+    Diag(Tok.getLocation(), diag::err_argument_required_after_attribute);
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delcypher wrote:

@pdherbemont Could you add a test case for this path?

https://github.com/llvm/llvm-project/pull/94216