[PATCH] D119664: Check for the overloadable attribute in all the appropriate syntactic locations

Aaron Ballman via Phabricator via cfe-commits cfe-commits at lists.llvm.org
Sun Feb 13 07:09:10 PST 2022

aaron.ballman created this revision.
aaron.ballman added reviewers: erichkeane, cor3ntin, rsmith.
aaron.ballman requested review of this revision.
Herald added a project: clang.

When forming the function type from a declarator, we look for an overloadable attribute before issuing a diagnostic in C about a function signature containing only `...`. When the attribute is present, we allow such a declaration for compatibility with the overloading rules in C++. However, we were not looking for the attribute in all of the places it is legal to write it on a declarator and so we only accepted the signature in some forms and incorrectly rejected the signature in others.

We now check for the attribute preceding the declarator instead of only being applied to the declarator directly.

  rG LLVM Github Monorepo



Index: clang/test/Sema/overloadable.c
--- clang/test/Sema/overloadable.c
+++ clang/test/Sema/overloadable.c
@@ -248,3 +248,14 @@
   // if take_fn is passed a void (**)(void *), we'll get a warning.
+// PR53805
+// We previously failed to consider the attribute being written before the
+// declaration when considering whether to allow a variadic signature with no
+// other parameters, and so we handled these cases differently.
+__attribute__((overloadable)) void can_overload_1(...); // ok, was previously rejected
+void can_overload_2(...) __attribute__((overloadable)); // ok
+[[clang::overloadable]] void can_overload_3(...);       // ok, was previously rejected
+void can_overload_4 [[clang::overloadable]] (...);      // ok
+void cannot_overload(...) [[clang::overloadable]];      // expected-error {{ISO C requires a named parameter before '...'}} \
+                                                        // expected-error {{'overloadable' attribute cannot be applied to types}}
Index: clang/lib/Sema/SemaType.cpp
--- clang/lib/Sema/SemaType.cpp
+++ clang/lib/Sema/SemaType.cpp
@@ -5237,7 +5237,9 @@
         // function is marked with the "overloadable" attribute. Scan
         // for this attribute now.
         if (!FTI.NumParams && FTI.isVariadic && !LangOpts.CPlusPlus)
-          if (!D.getAttributes().hasAttribute(ParsedAttr::AT_Overloadable))
+          if (!D.getAttributes().hasAttribute(ParsedAttr::AT_Overloadable) &&
+              !D.getDeclSpec().getAttributes().hasAttribute(
+                  ParsedAttr::AT_Overloadable))
             S.Diag(FTI.getEllipsisLoc(), diag::err_ellipsis_first_param);
         if (FTI.NumParams && FTI.Params[0].Param == nullptr) {
Index: clang/docs/ReleaseNotes.rst
--- clang/docs/ReleaseNotes.rst
+++ clang/docs/ReleaseNotes.rst
@@ -77,6 +77,9 @@
 - Added support for parameter pack expansion in `clang::annotate`.
+- The ``overloadable`` attribute can now be written in all of the syntactic
+  locations a declaration attribute may appear. Fixes PR53805.
 Windows Support

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