namespace std {
// types
typedef object type fenv_t;
typedef integer type fexcept_t;
// functions
int feclearexcept(int except);
int fegetexceptflag(fexcept_t *pflag, int except);
int feraiseexcept(int except);
int fesetexceptflag(const fexcept_t *pflag, int except);
int fetestexcept(int except);
int fegetround(void);
int fesetround(int mode);
int fegetenv(fenv_t *penv);
int feholdexcept(fenv_t *penv);
int fesetenv(const fenv_t *penv);
int feupdateenv(const fenv_t *penv);
}
The header also defines the macros:
FE_ALL_EXCEPT FE_DIVBYZERO FE_INEXACT FE_INVALID FE_OVERFLOW FE_UNDERFLOW FE_DOWNWARD FE_TONEAREST FE_TOWARDZERO FE_UPWARD FE_DFL_ENV
The header defines all functions, types, and macros the same as Clause 7.6 of the C standard.
The floating-point environment has thread storage duration ([basic.stc.thread]). The initial state for a thread's floating-point environment is the state of the floating-point environment of the thread that constructs the corresponding std::thread object ([thread.thread.class]) at the time it constructed the object. [ Note: That is, the child thread gets the floating-point state of the parent thread at the time of the child's creation. — end note ]
A separate floating-point environment shall be maintained for each thread. Each function accesses the environment corresponding to its calling thread.