| Functions | ||||
(C99) | ||||
(C99) | ||||
(C99) | ||||
(C99)(C99) | ||||
(C99)(C99) | ||||
fegetenvfesetenv (C99) | ||||
(C99) | ||||
(C99) | ||||
| Macro constants | ||||
(C99) |
Defined in header <fenv.h> | ||
int fegetenv( fenv_t* envp); | (1) | (since C99) |
int fesetenv(const fenv_t* envp); | (2) | (since C99) |
1) Attempts to store the status of the floating-point environment in the object pointed to byenvp.
2) Attempts to establish the floating-point environment from the object pointed to byenvp. The value of that object must be previously obtained by a call tofeholdexcept orfegetenv or be a floating-point macro constant. If any of the floating-point status flags are set inenvp, they become set in the environment (and are then testable withfetestexcept), but the corresponding floating-point exceptions are not raised (execution continues uninterrupted)
Contents |
| envp | - | pointer to the object of typefenv_t which holds the status of the floating-point environment |
0 on success, non-zero otherwise.
#include <stdio.h>#include <math.h>#include <fenv.h> #pragma STDC FENV_ACCESS ON void show_fe_exceptions(void){printf("current exceptions raised: ");if(fetestexcept(FE_DIVBYZERO))printf(" FE_DIVBYZERO");if(fetestexcept(FE_INEXACT))printf(" FE_INEXACT");if(fetestexcept(FE_INVALID))printf(" FE_INVALID");if(fetestexcept(FE_OVERFLOW))printf(" FE_OVERFLOW");if(fetestexcept(FE_UNDERFLOW))printf(" FE_UNDERFLOW");if(fetestexcept(FE_ALL_EXCEPT)==0)printf(" none");printf("\n");} void show_fe_rounding_method(void){printf("current rounding method: ");switch(fegetround()){caseFE_TONEAREST:printf("FE_TONEAREST");break;caseFE_DOWNWARD:printf("FE_DOWNWARD");break;caseFE_UPWARD:printf("FE_UPWARD");break;caseFE_TOWARDZERO:printf("FE_TOWARDZERO");break;default:printf("unknown");};printf("\n");} void show_fe_environment(void){ show_fe_exceptions(); show_fe_rounding_method();} int main(void){ fenv_t curr_env;int rtn; /* Show default environment. */ show_fe_environment();printf("\n"); /* Perform some computation under default environment. */printf("+11.5 -> %+4.1f\n",rint(+11.5));/* midway between two integers */printf("+12.5 -> %+4.1f\n",rint(+12.5));/* midway between two integers */ show_fe_environment();printf("\n"); /* Save current environment. */ rtn= fegetenv(&curr_env); /* Perform some computation with new rounding method. */feclearexcept(FE_ALL_EXCEPT);fesetround(FE_DOWNWARD);printf("1.0/0.0 = %f\n",1.0/0.0);printf("+11.5 -> %+4.1f\n",rint(+11.5));printf("+12.5 -> %+4.1f\n",rint(+12.5)); show_fe_environment();printf("\n"); /* Restore previous environment. */ rtn= fesetenv(&curr_env); show_fe_environment(); return0;}
Output:
current exceptions raised: nonecurrent rounding method: FE_TONEAREST +11.5 -> +12.0+12.5 -> +12.0current exceptions raised: FE_INEXACTcurrent rounding method: FE_TONEAREST 1.0/0.0 = inf+11.5 -> +11.0+12.5 -> +12.0current exceptions raised: FE_DIVBYZERO FE_INEXACTcurrent rounding method: FE_DOWNWARD current exceptions raised: FE_INEXACTcurrent rounding method: FE_TONEAREST
(C99) | saves the environment, clears all status flags and ignores all future errors (function)[edit] |
(C99) | restores the floating-point environment and raises the previously raise exceptions (function)[edit] |
(C99) | default floating-point environment (macro constant)[edit] |
C++ documentation forfegetenv,fesetenv | |
