[clang] Add getUnsignedPointerDiffType method

C11 standard refers to the unsigned counterpart of the type ptrdiff_t 
in the paragraph 7.21.6.1p7 where it defines the format specifier %tu.
In Clang (in PrintfFormatString.cpp, lines 508-510) there is a FIXME for this case,
in particular, Clang didn't diagnose %tu issues at all, i.e.
it didn't emit any warnings on the code printf("%tu", 3.14).
In this diff we add a method getUnsignedPointerDiffType for getting the corresponding type
similarly to how it's already done in the other analogous cases (size_t, ssize_t, ptrdiff_t etc)
and fix -Wformat diagnostics for %tu plus the emitted fix-it as well.

Test plan: make check-all

Differential revision: https://reviews.llvm.org/D38270

llvm-svn: 314470

3 files changed, 10 insertions, 5 deletions

diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
index 82e74528d19..2a607996531 100644
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -4571,6 +4571,13 @@ QualType ASTContext::getPointerDiffType() const {
   return getFromTargetType(Target->getPtrDiffType(0));
 }
 
+/// \brief Return the unique unsigned counterpart of "ptrdiff_t"
+/// integer type. The standard (C11 7.21.6.1p7) refers to this type
+/// in the definition of %tu format specifier.
+QualType ASTContext::getUnsignedPointerDiffType() const {
+  return getFromTargetType(Target->getUnsignedPtrDiffType(0));
+}
+
 /// \brief Return the unique type for "pid_t" defined in
 /// <sys/types.h>. We need this to compute the correct type for vfork().
 QualType ASTContext::getProcessIDType() const {
diff --git a/clang/lib/Analysis/PrintfFormatString.cpp b/clang/lib/Analysis/PrintfFormatString.cpp
index 26636376d1e..dfaed26564e 100644
--- a/clang/lib/Analysis/PrintfFormatString.cpp
+++ b/clang/lib/Analysis/PrintfFormatString.cpp
@@ -505,9 +505,7 @@ ArgType PrintfSpecifier::getArgType(ASTContext &Ctx,
                    ? ArgType(Ctx.UnsignedLongLongTy, "unsigned __int64")
                    : ArgType(Ctx.UnsignedIntTy, "unsigned __int32");
       case LengthModifier::AsPtrDiff:
-        // FIXME: How to get the corresponding unsigned
-        // version of ptrdiff_t?
-        return ArgType();
+        return ArgType(Ctx.getUnsignedPointerDiffType(), "unsigned ptrdiff_t");
       case LengthModifier::AsAllocate:
       case LengthModifier::AsMAllocate:
       case LengthModifier::AsWide:
diff --git a/clang/lib/Analysis/ScanfFormatString.cpp b/clang/lib/Analysis/ScanfFormatString.cpp
index 734dc7521c6..8398a4b82d5 100644
--- a/clang/lib/Analysis/ScanfFormatString.cpp
+++ b/clang/lib/Analysis/ScanfFormatString.cpp
@@ -291,8 +291,8 @@ ArgType ScanfSpecifier::getArgType(ASTContext &Ctx) const {
         case LengthModifier::AsSizeT:
           return ArgType::PtrTo(ArgType(Ctx.getSizeType(), "size_t"));
         case LengthModifier::AsPtrDiff:
-          // FIXME: Unsigned version of ptrdiff_t?
-          return ArgType();
+          return ArgType::PtrTo(
+              ArgType(Ctx.getUnsignedPointerDiffType(), "unsigned ptrdiff_t"));
         case LengthModifier::AsLongDouble:
           // GNU extension.
           return ArgType::PtrTo(Ctx.UnsignedLongLongTy);