Fixed-Point Types

_Fract data type _Accum data type _Sat data type hr fixed-suffix r fixed-suffix lr fixed-suffix llr fixed-suffix uhr fixed-suffix ur fixed-suffix ulr fixed-suffix ullr fixed-suffix hk fixed-suffix k fixed-suffix lk fixed-suffix llk fixed-suffix uhk fixed-suffix uk fixed-suffix ulk fixed-suffix ullk fixed-suffix HR fixed-suffix R fixed-suffix LR fixed-suffix LLR fixed-suffix UHR fixed-suffix UR fixed-suffix ULR fixed-suffix ULLR fixed-suffix HK fixed-suffix K fixed-suffix LK fixed-suffix LLK fixed-suffix UHK fixed-suffix UK fixed-suffix ULK fixed-suffix ULLK fixed-suffix

As an extension, GNU C supports fixed-point types as defined in the N1169 draft of ISO/IEC DTR 18037. Support for fixed-point types in GCC will evolve as the draft technical report changes. Calling conventions for any target might also change. Not all targets support fixed-point types.

The fixed-point types are short _Fract, _Fract, long _Fract, long long _Fract, unsigned short _Fract, unsigned _Fract, unsigned long _Fract, unsigned long long _Fract, _Sat short _Fract, _Sat _Fract, _Sat long _Fract, _Sat long long _Fract, _Sat unsigned short _Fract, _Sat unsigned _Fract, _Sat unsigned long _Fract, _Sat unsigned long long _Fract, short _Accum, _Accum, long _Accum, long long _Accum, unsigned short _Accum, unsigned _Accum, unsigned long _Accum, unsigned long long _Accum, _Sat short _Accum, _Sat _Accum, _Sat long _Accum, _Sat long long _Accum, _Sat unsigned short _Accum, _Sat unsigned _Accum, _Sat unsigned long _Accum, _Sat unsigned long long _Accum.

Fixed-point data values contain fractional and optional integral parts. The format of fixed-point data varies and depends on the target machine.

Support for fixed-point types includes:

• prefix and postfix increment and decrement operators (++, --) * unary arithmetic operators (+, -, !) * binary arithmetic operators (+, -, *, /) * binary shift operators (<<, >>) * relational operators (<, <=, >=, >) * equality operators (==, !=) * assignment operators (+=, -=, *=, /=, <<=, >>=) * conversions to and from integer, floating-point, or fixed-point types

Use a suffix in a fixed-point literal constant:

• hr or HR for short _Fract and _Sat short _Fract * r or R for _Fract and _Sat _Fract * lr or LR for long _Fract and _Sat long _Fract * llr or LLR for long long _Fract and _Sat long long _Fract * uhr or UHR for unsigned short _Fract and _Sat unsigned short _Fract * ur or UR for unsigned _Fract and _Sat unsigned _Fract * ulr or ULR for unsigned long _Fract and _Sat unsigned long _Fract * ullr or ULLR for unsigned long long _Fract and _Sat unsigned long long _Fract * hk or HK for short _Accum and _Sat short _Accum * k or K for _Accum and _Sat _Accum * lk or LK for long _Accum and _Sat long _Accum * llk or LLK for long long _Accum and _Sat long long _Accum * uhk or UHK for unsigned short _Accum and _Sat unsigned short _Accum * uk or UK for unsigned _Accum and _Sat unsigned _Accum * ulk or ULK for unsigned long _Accum and _Sat unsigned long _Accum * ullk or ULLK for unsigned long long _Accum and _Sat unsigned long long _Accum

GCC support of fixed-point types as specified by the draft technical report is incomplete:

• Pragmas to control overflow and rounding behaviors are not implemented.

Fixed-point types are supported by the DWARF 2 debug information format.