r313907 - Suppress Wsign-conversion for enums with matching underlying type

[Erich Keane via cfe-commits]

Author: erichkeane
Date: Thu Sep 21 12:58:55 2017
New Revision: 313907

URL: http://llvm.org/viewvc/llvm-project?rev=313907&view=rev
Log:
Suppress Wsign-conversion for enums with matching underlying type

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.

Differential Revision: https://reviews.llvm.org/D38145

Modified:
    cfe/trunk/lib/Sema/SemaChecking.cpp

Modified: cfe/trunk/lib/Sema/SemaChecking.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaChecking.cpp?rev=313907&r1=313906&r2=313907&view=diff
==============================================================================
--- cfe/trunk/lib/Sema/SemaChecking.cpp (original)
+++ cfe/trunk/lib/Sema/SemaChecking.cpp Thu Sep 21 12:58:55 2017
@@ -8171,8 +8171,11 @@ struct IntRange {
     // For enum types, use the known bit width of the enumerators.
     if (const EnumType *ET = dyn_cast<EnumType>(T)) {
       EnumDecl *Enum = ET->getDecl();
+      // In C++11, enums without definitions can have an explicitly specified
+      // underlying type.  Use this type to compute the range.
       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();