PR10828: Produce a warning when a no-arguments function is declared in block

scope, when no other indication is provided that the user intended to declare a
function rather than a variable.

Remove some false positives from the existing 'parentheses disambiguated as a
function' warning by suppressing it when the declaration is marked as 'typedef'
or 'extern'.

Add a new warning group -Wvexing-parse containing both of these warnings.

The new warning is enabled by default; despite a number of false positives (and
one bug) in clang's test-suite, I have only found genuine bugs with it when
running it over a significant quantity of real C++ code.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@147599 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 15 insertions, 0 deletions

diff --git a/lib/Parse/ParseDecl.cpp b/lib/Parse/ParseDecl.cpp
index ee4a51e184..d3c8211372 100644
--- a/lib/Parse/ParseDecl.cpp
+++ b/lib/Parse/ParseDecl.cpp
@@ -1111,6 +1111,21 @@ Parser::DeclGroupPtrTy Parser::ParseDeclGroup(ParsingDeclSpec &DS,
   if (FirstDecl)
     DeclsInGroup.push_back(FirstDecl);
 
+  // In C++, "T var();" at block scope is probably an attempt to initialize a
+  // variable, not a function declaration. We don't catch this case earlier,
+  // since there is no ambiguity here.
+  if (getLang().CPlusPlus && Context != Declarator::FileContext &&
+      D.getNumTypeObjects() == 1 && D.isFunctionDeclarator() &&
+      D.getDeclSpec().getStorageClassSpecAsWritten()
+        == DeclSpec::SCS_unspecified &&
+      D.getDeclSpec().getTypeSpecType() != DeclSpec::TST_void) {
+    DeclaratorChunk &C = D.getTypeObject(0);
+    if (C.Fun.NumArgs == 0 && !C.Fun.isVariadic && !C.Fun.TrailingReturnType &&
+        C.Fun.getExceptionSpecType() == EST_None)
+      Diag(C.Loc, diag::warn_empty_parens_are_function_decl)
+        << SourceRange(C.Loc, C.EndLoc);
+  }
+
   bool ExpectSemi = Context != Declarator::ForContext;
 
   // If we don't have a comma, it is either the end of the list (a ';') or an