Implement GCC's -Wint-to-pointer-cast.

This implementation doesn't warn on anything that GCC doesn't warn on with the
exception of templates specializations (GCC doesn't warn, Clang does). The
specific skipped cases (boolean, constant expressions, enums) are open for
debate/adjustment if anyone wants to demonstrate that GCC is being overly
conservative here. The only really obvious false positive I found was in the
Clang regression suite's MPI test - apparently MPI uses specific flag values in
pointer constants. (eg: #define FOO (void*)~0)

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@166039 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 20 insertions, 0 deletions

diff --git a/lib/Sema/SemaCast.cpp b/lib/Sema/SemaCast.cpp
index 0c3757821e..bf25c61785 100644
--- a/lib/Sema/SemaCast.cpp
+++ b/lib/Sema/SemaCast.cpp
@@ -1491,6 +1491,22 @@ static void DiagnoseCastOfObjCSEL(Sema &Self, const ExprResult &SrcExpr,
     }
 }
 
+static void checkIntToPointerCast(bool CStyle, SourceLocation Loc,
+                                  const Expr *SrcExpr, QualType DestType,
+                                  Sema &Self) {
+  QualType SrcType = SrcExpr->getType();
+
+  // Not warning on reinterpret_cast, boolean, constant expressions, etc
+  // are not explicit design choices, but consistent with GCC's behavior.
+  // Feel free to modify them if you've reason/evidence for an alternative.
+  if (CStyle && SrcType->isIntegralType(Self.Context)
+      && !SrcType->isBooleanType()
+      && !SrcType->isEnumeralType()
+      && !SrcExpr->isIntegerConstantExpr(Self.Context)
+      && Self.Context.getTypeSize(DestType) > Self.Context.getTypeSize(SrcType))
+    Self.Diag(Loc, diag::warn_int_to_pointer_cast) << SrcType << DestType;
+}
+
 static TryCastResult TryReinterpretCast(Sema &Self, ExprResult &SrcExpr,
                                         QualType DestType, bool CStyle,
                                         const SourceRange &OpRange,
@@ -1689,6 +1705,8 @@ static TryCastResult TryReinterpretCast(Sema &Self, ExprResult &SrcExpr,
 
   if (SrcType->isIntegralOrEnumerationType()) {
     assert(destIsPtr && "One type must be a pointer");
+    checkIntToPointerCast(CStyle, OpRange.getBegin(), SrcExpr.get(), DestType,
+                          Self);
     // C++ 5.2.10p5: A value of integral or enumeration type can be explicitly
     //   converted to a pointer.
     // C++ 5.2.10p9: [Note: ...a null pointer constant of integral type is not
@@ -2071,6 +2089,8 @@ void CastOperation::CheckCStyleCast() {
       SrcExpr = ExprError();
       return;
     }
+    checkIntToPointerCast(/* CStyle */ true, OpRange.getBegin(), SrcExpr.get(),
+                          DestType, Self);
   } else if (!SrcType->isArithmeticType()) {
     if (!DestType->isIntegralType(Self.Context) &&
         DestType->isArithmeticType()) {