What uncommon floating-point sizes exist in C++ compilers?

Question

The C++14 draft standard seems rather quiet about the specific requirements for float, double and long double, although these sizes seem to be common:

Answer 1

First of, I am new to stackoverflow, so please bear with me.

However, to answer your question. Looking at the floath.h headers, which specify floating point parameters for the:

1. Intel Compiler

   //Float:
   #define FLT_MAX                 3.40282347e+38F
   
   //Double:
   #define DBL_MAX                 1.7976931348623157e+308
   
   //Long Double:
   #if (__IMFLONGDOUBLE == 64) || defined(__LONGDOUBLE_AS_DOUBLE)
   #define LDBL_MAX                    1.7976931348623157e+308L
   #else
   #define LDBL_MAX                1.1897314953572317650213E+4932L
   

2. GCC (MinGW actually gcc 4 or 5)

   //Float:
   #define FLT_MAX         3.40282347e+38F
   
   //Double:
   #define DBL_MAX     1.7976931348623157e+308
   
   //Long Double: (same as double for gcc):
   #define LDBL_MAX        1.7976931348623157e+308L
   

3. Microsoft

   //Float:
   #define FLT_MAX         3.40282347e+38F
   
   //Double:
   #define DBL_MAX     1.7976931348623157e+308
   
   //Long Double: (same as double for Microsoft):
   #define LDBL_MAX            DBL_MAX
   

So, as you can see only the Intel compiler provides 80 bit representation for long double on a "standard" windows machine.

This data is copied from the respective float.h headers from a windows machine.