2 files changed, 19 insertions, 2 deletions
diff --git a/lib/Analysis/PrintfFormatString.cpp b/lib/Analysis/PrintfFormatString.cpp
index 0c0e343331..4e3e391fd0 100644
--- a/lib/Analysis/PrintfFormatString.cpp
+++ b/lib/Analysis/PrintfFormatString.cpp
@@ -355,7 +355,7 @@ ArgTypeResult PrintfSpecifier::getArgType(ASTContext &Ctx) const {
   return ArgTypeResult();
 }
 
-bool PrintfSpecifier::fixType(QualType QT) {
+bool PrintfSpecifier::fixType(QualType QT, const LangOptions &LangOpt) {
   // Handle strings first (char *, wchar_t *)
   if (QT->isPointerType() && (QT->getPointeeType()->isAnyCharacterType())) {
     CS.setKind(ConversionSpecifier::sArg);
@@ -438,6 +438,23 @@ bool PrintfSpecifier::fixType(QualType QT) {
     break;
   }
 
+  // Handle size_t, ptrdiff_t, etc. that have dedicated length modifiers in C99.
+  if (isa<TypedefType>(QT) && (LangOpt.C99 || LangOpt.CPlusPlus0x)) {
+    const IdentifierInfo *Identifier = QT.getBaseTypeIdentifier();
+    if (Identifier->getName() == "size_t") {
+      LM.setKind(LengthModifier::AsSizeT);
+    } else if (Identifier->getName() == "ssize_t") {
+      // Not C99, but common in Unix.
+      LM.setKind(LengthModifier::AsSizeT);
+    } else if (Identifier->getName() == "intmax_t") {
+      LM.setKind(LengthModifier::AsIntMax);
+    } else if (Identifier->getName() == "uintmax_t") {
+      LM.setKind(LengthModifier::AsIntMax);
+    } else if (Identifier->getName() == "ptrdiff_t") {
+      LM.setKind(LengthModifier::AsPtrDiff);
+    }
+  }
+
   // Set conversion specifier and disable any flags which do not apply to it.
   // Let typedefs to char fall through to int, as %c is silly for uint8_t.
   if (isa<TypedefType>(QT) && QT->isAnyCharacterType()) {
diff --git a/lib/Sema/SemaChecking.cpp b/lib/Sema/SemaChecking.cpp
index 329adf89e8..fd99528bd6 100644
--- a/lib/Sema/SemaChecking.cpp
+++ b/lib/Sema/SemaChecking.cpp
@@ -1966,7 +1966,7 @@ CheckPrintfHandler::HandlePrintfSpecifier(const analyze_printf::PrintfSpecifier
 
     // We may be able to offer a FixItHint if it is a supported type.
     PrintfSpecifier fixedFS = FS;
-    bool success = fixedFS.fixType(Ex->getType());
+    bool success = fixedFS.fixType(Ex->getType(), S.getLangOptions());
 
     if (success) {
       // Get the fix string from the fixed format specifier