As an extension, GNU C supports additional floating
types, __float80 and __float128 to support 80-bit
(XFmode) and 128-bit (TFmode) floating types.
Support for additional types includes the arithmetic operators:
add, subtract, multiply, divide; unary arithmetic operators;
relational operators; equality operators; and conversions to and from
integer and other floating types. Use a suffix ‘w’ or ‘W’
in a literal constant of type __float80 and ‘q’ or ‘Q’
for _float128. You can declare complex types using the
corresponding internal complex type, XCmode for __float80
type and TCmode for __float128 type:
typedef _Complex float __attribute__((mode(TC))) _Complex128;
typedef _Complex float __attribute__((mode(XC))) _Complex80;
Not all targets support additional floating-point types. __float80
and __float128 types are supported on i386, x86_64 and IA-64 targets.
The __float128 type is supported on hppa HP-UX targets.