Warn on va_start() when called with a reference parameter.

http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2005/n1905.pdf 18.7p3
explicitly calls this (and some other things) out as undefined.

Also move 2 other existing warnings behind the new -Wvarargs flag.

llvm-svn: 182694

1 files changed, 14 insertions, 0 deletions

diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp
index 3471c004406..cdc546c4761 100644
--- a/clang/lib/Sema/SemaChecking.cpp
+++ b/clang/lib/Sema/SemaChecking.cpp
@@ -1355,6 +1355,11 @@ bool Sema::SemaBuiltinVAStart(CallExpr *TheCall) {
   bool SecondArgIsLastNamedArgument = false;
   const Expr *Arg = TheCall->getArg(1)->IgnoreParenCasts();
 
+  // These are valid if SecondArgIsLastNamedArgument is false after the next
+  // block.
+  QualType Type;
+  SourceLocation ParamLoc;
+
   if (const DeclRefExpr *DR = dyn_cast<DeclRefExpr>(Arg)) {
     if (const ParmVarDecl *PV = dyn_cast<ParmVarDecl>(DR->getDecl())) {
       // FIXME: This isn't correct for methods (results in bogus warning).
@@ -1367,12 +1372,21 @@ bool Sema::SemaBuiltinVAStart(CallExpr *TheCall) {
       else
         LastArg = *(getCurMethodDecl()->param_end()-1);
       SecondArgIsLastNamedArgument = PV == LastArg;
+
+      Type = PV->getType();
+      ParamLoc = PV->getLocation();
     }
   }
 
   if (!SecondArgIsLastNamedArgument)
     Diag(TheCall->getArg(1)->getLocStart(),
          diag::warn_second_parameter_of_va_start_not_last_named_argument);
+  else if (Type->isReferenceType()) {
+    Diag(Arg->getLocStart(),
+         diag::warn_va_start_of_reference_type_is_undefined);
+    Diag(ParamLoc, diag::note_parameter_type) << Type;
+  }
+
   return false;
 }