Make __builtin_types_compatible_p more like GCC's

GCC ignore qualifiers on array types. Since we seem to have this
function primarily for GCC compatibility, we should try to match that
behavior.

This also adds a few more test-cases __builtin_types_compatible_p,
which were inspired by GCC's documentation on the builtin.

llvm-svn: 315951

2 files changed, 24 insertions, 3 deletions

diff --git a/clang/lib/Sema/SemaExprCXX.cpp b/clang/lib/Sema/SemaExprCXX.cpp
index 17aa8847e03..7f5b792e8c4 100644
--- a/clang/lib/Sema/SemaExprCXX.cpp
+++ b/clang/lib/Sema/SemaExprCXX.cpp
@@ -4824,9 +4824,13 @@ static bool EvaluateBinaryTypeTrait(Sema &Self, TypeTrait BTT, QualType LhsT,
   }
   case BTT_IsSame:
     return Self.Context.hasSameType(LhsT, RhsT);
-  case BTT_TypeCompatible:
-    return Self.Context.typesAreCompatible(LhsT.getUnqualifiedType(),
-                                           RhsT.getUnqualifiedType());
+  case BTT_TypeCompatible: {
+    // GCC ignores cv-qualifiers on arrays for this builtin.
+    Qualifiers LhsQuals, RhsQuals;
+    QualType Lhs = Self.getASTContext().getUnqualifiedArrayType(LhsT, LhsQuals);
+    QualType Rhs = Self.getASTContext().getUnqualifiedArrayType(RhsT, RhsQuals);
+    return Self.Context.typesAreCompatible(Lhs, Rhs);
+  }
   case BTT_IsConvertible:
   case BTT_IsConvertibleTo: {
     // C++0x [meta.rel]p4:
diff --git a/clang/test/Parser/builtin_types_compatible.c b/clang/test/Parser/builtin_types_compatible.c
index ac81e7b08dc..d967a7023a4 100644
--- a/clang/test/Parser/builtin_types_compatible.c
+++ b/clang/test/Parser/builtin_types_compatible.c
@@ -41,3 +41,20 @@ static void test()
 
 }
 
+enum E1 { E1Foo };
+enum E2 { E2Foo };
+
+static void testGccCompatibility() {
+  _Static_assert(__builtin_types_compatible_p(const volatile int, int), "");
+  _Static_assert(__builtin_types_compatible_p(int[5], int[]), "");
+  _Static_assert(!__builtin_types_compatible_p(int[5], int[4]), "");
+  _Static_assert(!__builtin_types_compatible_p(int *, int **), "");
+  _Static_assert(!__builtin_types_compatible_p(const int *, int *), "");
+  _Static_assert(!__builtin_types_compatible_p(enum E1, enum E2), "");
+
+  // GCC's __builtin_types_compatible_p ignores qualifiers on arrays.
+  _Static_assert(__builtin_types_compatible_p(const int[4], int[4]), "");
+  _Static_assert(__builtin_types_compatible_p(int[4], const int[4]), "");
+  _Static_assert(__builtin_types_compatible_p(const int[5][4], int[][4]), "");
+  _Static_assert(!__builtin_types_compatible_p(const int(*)[], int(*)[]), "");
+}