is this compiller error

/*

Following code compiled with clang-cl on win10 generates 2 errors
(while the same code compiled with MS cl compiles):

t1.cpp(12,35): error: in-class initializer for static data member is not a constant expression
       static const int64_t MIN_VALUE = -0x8000000000000000LL;
                                        ^~~~~~~~~~~~~~~~~~~~~
t1.cpp(15,39): error: in-class initializer for static data member is not a constant expression
   static const int64_t MIN_VALUE1 = -9223372036854775808LL;
                                     ^~~~~~~~~~~~~~~~~~~~~~
2 errors generated.

*/

#include <string>

static const int64_t MAX_VALUE = 0x7fffffffffffffffLL;
static const int64_t MIN_VALUE = -0x8000000000000000LL;

static const int64_t MAX_VALUE1 = 9223372036854775807LL;
static const int64_t MIN_VALUE1 = -9223372036854775808LL;

class XÂ {
   static const int64_t MAX_VALUE = 0x7fffffffffffffffLL;
   static const int64_t MIN_VALUE = -0x8000000000000000LL;

   static const int64_t MAX_VALUE1 = 9223372036854775807LL;
   static const int64_t MIN_VALUE1 = -9223372036854775808LL;
};

/*

Following code compiled with clang-cl on win10 generates 2 errors
(while the same code compiled with MS cl compiles):

t1.cpp(12,35): error: in-class initializer for static data member is not
a constant expression
static const int64_t MIN_VALUE = -0x8000000000000000LL;
^~~~~~~~~~~~~~~~~~~~~
t1.cpp(15,39): error: in-class initializer for static data member is not
a constant expression
static const int64_t MIN_VALUE1 = -9223372036854775808LL;
^~~~~~~~~~~~~~~~~~~~~~
2 errors generated.

These expressions have undefined behavior due to exhibiting signed overflow, and so are non-constant in C++11 onwards.