[PATCH] Fix recognition of empty structures/unions

[Richard Smith]

================
Comment at: lib/Sema/SemaDecl.cpp:11038-11039
@@ +11037,4 @@
+    if (!getLangOpts().CPlusPlus) {
+      bool is_empty = true;
+      bool no_named = true;
+      for (RecordDecl::field_iterator i = Record->field_begin(),
----------------
Variable names should be CamelCase with a leading capital letter.

================
Comment at: lib/Sema/SemaDecl.cpp:11045-11046
@@ +11044,4 @@
+            is_empty = false;
+        }
+        else
+          no_named = is_empty = false;
----------------
} and else should be on the same line.

================
Comment at: lib/Sema/SemaDecl.cpp:11049-11059
@@ +11048,13 @@
+      }
+      if (is_empty) {
+        // Empty structs are an extension in C (C99 6.7.2.1p7), but are allowed in
+        // C++.
+        Diag(RecLoc, diag::ext_empty_struct_union) << Record->isUnion();
+        Diag(RecLoc, diag::warn_empty_struct_union_compat) << Record->isUnion();
+      }
+      else if (no_named) {
+        // Structs without named members are extension in C (C99 6.7.2.1p7), but
+        // are accepted by GCC.
+        Diag(RecLoc, diag::ext_no_named_members_in_struct_union) << Record->isUnion();
+      }
+    }
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Either use the "without named members" diagnostic in both cases where no_named is true, or actually track whether the struct is empty (that is, has no members, not even empty bitfields). We shouldn't claim that "struct S { unsigned : 0; };" is empty.


http://llvm-reviews.chandlerc.com/D578