Gcc/10.2.0/gcc/Fixed 002dPoint
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6.16 Fixed-Point Types
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
’ forshort _Fract
and_Sat short _Fract
- ‘
r
’ or ‘R
’ for_Fract
and_Sat _Fract
- ‘
lr
’ or ‘LR
’ forlong _Fract
and_Sat long _Fract
- ‘
llr
’ or ‘LLR
’ forlong long _Fract
and_Sat long long _Fract
- ‘
uhr
’ or ‘UHR
’ forunsigned short _Fract
and_Sat unsigned short _Fract
- ‘
ur
’ or ‘UR
’ forunsigned _Fract
and_Sat unsigned _Fract
- ‘
ulr
’ or ‘ULR
’ forunsigned long _Fract
and_Sat unsigned long _Fract
- ‘
ullr
’ or ‘ULLR
’ forunsigned long long _Fract
and_Sat unsigned long long _Fract
- ‘
hk
’ or ‘HK
’ forshort _Accum
and_Sat short _Accum
- ‘
k
’ or ‘K
’ for_Accum
and_Sat _Accum
- ‘
lk
’ or ‘LK
’ forlong _Accum
and_Sat long _Accum
- ‘
llk
’ or ‘LLK
’ forlong long _Accum
and_Sat long long _Accum
- ‘
uhk
’ or ‘UHK
’ forunsigned short _Accum
and_Sat unsigned short _Accum
- ‘
uk
’ or ‘UK
’ forunsigned _Accum
and_Sat unsigned _Accum
- ‘
ulk
’ or ‘ULK
’ forunsigned long _Accum
and_Sat unsigned long _Accum
- ‘
ullk
’ or ‘ULLK
’ forunsigned 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 debug information format.
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