Compiler Warning (level 4) C4480
nonstandard extension used: specifying underlying type for enum 'enum'
An extension to the language under /clr was used without /clr. You can disable C4480 with the warning pragma.
For more information, see /clr (Common Language Runtime Compilation), /Za, /Ze (Disable Language Extensions), enum class, and C++ Enumeration Declarations.
Example
The following sample generates C4480.
// C4480.cpp
// compile with: /W4 /c
enum E : char {}; // C4480
enum F {};