F.7.1 Environment management

1

IEC 60559 requires that floating-point operations implicitly raise floating-point exception status flags, and that rounding control modes can be set explicitly to affect result values of floating-point operations. When the state for the FENV_ACCESS pragma (defined in <fenv.h>) is “on”, these changes to the floating-point state are treated as side effects which respect sequence points.[1]

Footnotes

[1]

If the state for the FENV_ACCESS pragma is “off”, the implementation is free to assume the floating- point control modes will be the default ones and the floating-point status flags will not be tested, which allows certain optimizations (see F.8).