[
Note 1:
This document does not require an implementation to support the
FENV_ACCESS pragma;
it is
implementation-defined (
[cpp.pragma])
whether the pragma is supported
. As a consequence,
it is
implementation-defined
whether these functions can be used to test floating-point status flags,
set floating-point control modes, or run under non-default mode settings
. If the pragma is used to enable control over the floating-point environment,
this document does not specify the effect on
floating-point evaluation in constant expressions
. —
end note]