Make -Wformat check the argument type for %n.

This makes Clang check that the corresponding argument for "%n" in a
format string is a pointer to int.

llvm-svn: 160966

1 files changed, 7 insertions, 0 deletions

diff --git a/clang/lib/Analysis/ScanfFormatString.cpp b/clang/lib/Analysis/ScanfFormatString.cpp
index 5c7e6ef8f27..3c848f1f093 100644
--- a/clang/lib/Analysis/ScanfFormatString.cpp
+++ b/clang/lib/Analysis/ScanfFormatString.cpp
@@ -303,6 +303,9 @@ ScanfArgTypeResult ScanfSpecifier::getArgType(ASTContext &Ctx) const {
     case ConversionSpecifier::pArg:
       return ScanfArgTypeResult(ArgTypeResult(ArgTypeResult::CPointerTy));
 
+    case ConversionSpecifier::nArg:
+      return ArgTypeResult(Ctx.IntTy);
+
     default:
       break;
   }
@@ -315,6 +318,10 @@ bool ScanfSpecifier::fixType(QualType QT, const LangOptions &LangOpt,
   if (!QT->isPointerType())
     return false;
 
+  // %n is different from other conversion specifiers; don't try to fix it.
+  if (CS.getKind() == ConversionSpecifier::nArg)
+    return false;
+
   QualType PT = QT->getPointeeType();
 
   // If it's an enum, get its underlying type.