DR583, DR1512: Implement a rewrite to C++'s 'composite pointer type' rules.

This has two significant effects:

1) Direct relational comparisons between null pointer constants (0 and nullopt)
   and pointers are now ill-formed. This was always the case for C, and it
   appears that C++ only ever permitted by accident. For instance, cases like
     nullptr < &a
   are now rejected.

2) Comparisons and conditional operators between differently-cv-qualified
   pointer types now work, and produce a composite type that both source
   pointer types can convert to (when possible). For instance, comparison
   between 'int **' and 'const int **' is now valid, and uses an intermediate
   type of 'const int *const *'.

Clang previously supported #2 as an extension.

We do not accept the cases in #1 as an extension. I've tested a fair amount of
code to check that this doesn't break it, but if it turns out that someone is
relying on this, we can easily add it back as an extension.

llvm-svn: 284800

2 files changed, 4 insertions, 10 deletions

diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index ede1d9e3a08..974f3bd02cc 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -5536,6 +5536,8 @@ def ext_typecheck_ordered_comparison_of_pointer_integer : ExtWarn<
   "ordered comparison between pointer and integer (%0 and %1)">;
 def ext_typecheck_ordered_comparison_of_pointer_and_zero : Extension<
   "ordered comparison between pointer and zero (%0 and %1) is an extension">;
+def err_typecheck_ordered_comparison_of_pointer_and_zero : Error<
+  "ordered comparison between pointer and zero (%0 and %1)">;
 def ext_typecheck_ordered_comparison_of_function_pointers : ExtWarn<
   "ordered comparison of function pointers (%0 and %1)">;
 def ext_typecheck_comparison_of_fptr_to_void : Extension<
@@ -5556,9 +5558,6 @@ def err_cond_voidptr_arc : Error <
   "in ARC mode">;
 def err_typecheck_comparison_of_distinct_pointers : Error<
   "comparison of distinct pointer types%diff{ ($ and $)|}0,1">;
-def ext_typecheck_comparison_of_distinct_pointers_nonstandard : ExtWarn<
-  "comparison of distinct pointer types (%0 and %1) uses non-standard "
-  "composite pointer type %2">, InGroup<CompareDistinctPointerType>;
 def err_typecheck_op_on_nonoverlapping_address_space_pointers : Error<
   "%select{comparison between %diff{ ($ and $)|}0,1"
   "|arithmetic operation with operands of type %diff{ ($ and $)|}0,1"
@@ -6837,9 +6836,6 @@ def err_typecheck_expect_scalar_operand : Error<
   "operand of type %0 where arithmetic or pointer type is required">;
 def err_typecheck_cond_incompatible_operands : Error<
   "incompatible operand types%diff{ ($ and $)|}0,1">;
-def ext_typecheck_cond_incompatible_operands_nonstandard : ExtWarn<
-  "incompatible operand types%diff{ ($ and $)|}0,1 use non-standard composite "
-  "pointer type %2">;
 def err_cast_selector_expr : Error<
   "cannot type cast @selector expression">;
 def ext_typecheck_cond_incompatible_pointers : ExtWarn<
diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
index 08e6a29ca11..951d5c4e7d0 100644
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -8954,15 +8954,13 @@ public:
     ExprResult &cond, ExprResult &lhs, ExprResult &rhs,
     ExprValueKind &VK, ExprObjectKind &OK, SourceLocation questionLoc);
   QualType FindCompositePointerType(SourceLocation Loc, Expr *&E1, Expr *&E2,
-                                    bool *NonStandardCompositeType = nullptr,
                                     bool ConvertArgs = true);
   QualType FindCompositePointerType(SourceLocation Loc,
                                     ExprResult &E1, ExprResult &E2,
-                                    bool *NonStandardCompositeType = nullptr,
                                     bool ConvertArgs = true) {
     Expr *E1Tmp = E1.get(), *E2Tmp = E2.get();
-    QualType Composite = FindCompositePointerType(
-        Loc, E1Tmp, E2Tmp, NonStandardCompositeType, ConvertArgs);
+    QualType Composite =
+        FindCompositePointerType(Loc, E1Tmp, E2Tmp, ConvertArgs);
     E1 = E1Tmp;
     E2 = E2Tmp;
     return Composite;