[PATCH] D38145: Suppress Wsign-conversion for enums with matching underlying type

[Erich Keane via Phabricator via cfe-commits]

erichkeane created this revision.

As reported here: https://bugs.llvm.org/show_bug.cgi?id=34692

A non-defined enum with a backing type was always defaulting to 
being treated as a signed type.  IN the case where it IS defined,
the signed-ness of the actual items is used.

This patch uses the underlying type's signed-ness in the non-defined
case to test signed-comparision.


https://reviews.llvm.org/D38145

Files:
  lib/Sema/SemaChecking.cpp
  test/SemaCXX/sign-conversion.cpp


Index: test/SemaCXX/sign-conversion.cpp
===================================================================
--- /dev/null
+++ test/SemaCXX/sign-conversion.cpp
@@ -0,0 +1,21 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -Wsign-conversion -std=c++11 %s
+
+unsigned int test() {
+  short foo;
+  return foo; // expected-warning {{implicit conversion changes signedness}}
+
+}
+
+unsigned int test3() {
+  // For a non-defined enum, use the underlying type.
+  enum u8 : char;
+  u8 foo{static_cast<u8>(0)};
+  return foo; // expected-warning {{implicit conversion changes signedness}}
+
+}
+unsigned int test2() {
+  // For a non-defined enum, use the underlying type.
+  enum u8 : unsigned char;
+  u8 foo{static_cast<u8>(0)};
+  return foo;
+}
Index: lib/Sema/SemaChecking.cpp
===================================================================
--- lib/Sema/SemaChecking.cpp
+++ lib/Sema/SemaChecking.cpp
@@ -8172,7 +8172,8 @@
     if (const EnumType *ET = dyn_cast<EnumType>(T)) {
       EnumDecl *Enum = ET->getDecl();
       if (!Enum->isCompleteDefinition())
-        return IntRange(C.getIntWidth(QualType(T, 0)), false);
+        return IntRange(C.getIntWidth(QualType(T, 0)),
+                        !ET->isSignedIntegerOrEnumerationType());
 
       unsigned NumPositive = Enum->getNumPositiveBits();
       unsigned NumNegative = Enum->getNumNegativeBits();


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