- The accuracy of the floating-point operations and of the library
functions in
<math.h> and <complex.h> that return floating-point
results (C90 and C99 5.2.4.2.2).
The accuracy is unknown.
- The rounding behaviors characterized by non-standard values
of
FLT_ROUNDS
(C90 and C99 5.2.4.2.2).
GCC does not use such values.
- The evaluation methods characterized by non-standard negative
values of
FLT_EVAL_METHOD (C99 5.2.4.2.2).
GCC does not use such values.
- The direction of rounding when an integer is converted to a
floating-point number that cannot exactly represent the original
value (C90 6.2.1.3, C99 6.3.1.4).
C99 Annex F is followed.
- The direction of rounding when a floating-point number is
converted to a narrower floating-point number (C90 6.2.1.4, C99
6.3.1.5).
C99 Annex F is followed.
- How the nearest representable value or the larger or smaller
representable value immediately adjacent to the nearest representable
value is chosen for certain floating constants (C90 6.1.3.1, C99
6.4.4.2).
C99 Annex F is followed.
- Whether and how floating expressions are contracted when not
disallowed by the
FP_CONTRACT pragma (C99 6.5).
Expressions are currently only contracted if
-funsafe-math-optimizations or -ffast-math are used.
This is subject to change.
- The default state for the
FENV_ACCESS pragma (C99 7.6.1).
This pragma is not implemented, but the default is to “off” unless
-frounding-math is used in which case it is “on”.
- Additional floating-point exceptions, rounding modes, environments,
and classifications, and their macro names (C99 7.6, C99 7.12).
This is dependent on the implementation of the C library, and is not
defined by GCC itself.
- The default state for the
FP_CONTRACT pragma (C99 7.12.2).
This pragma is not implemented. Expressions are currently only
contracted if -funsafe-math-optimizations or
-ffast-math are used. This is subject to change.
- Whether the “inexact” floating-point exception can be raised
when the rounded result actually does equal the mathematical result
in an IEC 60559 conformant implementation (C99 F.9).
This is dependent on the implementation of the C library, and is not
defined by GCC itself.
- Whether the “underflow” (and “inexact”) floating-point
exception can be raised when a result is tiny but not inexact in an
IEC 60559 conformant implementation (C99 F.9).
This is dependent on the implementation of the C library, and is not
defined by GCC itself.