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在头文件<fenv.h>中定义



#define FE_DIVBYZERO    /*implementation defined power of 2*/


(自C99)

#define FE_INEXACT      /*implementation defined power of 2*/


(自 C99)

#define FE_INVALID      /*implementation defined power of 2*/


(自C99)

#define FE_OVERFLOW     /*implementation defined power of 2*/


(自C99)

#define FE_UNDERFLOW    /*implementation defined power of 2*/


(自C99)

#define FE_ALL_EXCEPT  FE_DIVBYZERO | FE_INEXACT | \                        FE_INVALID | FE_OVERFLOW |  \                        FE_UNDERFLOW


(自 C99)

所有这些宏常量（FE_ALL_EXCEPT除外）都展开为不同幂的2的整型常量表达式，它们唯一标识所有受支持的浮点异常。 每个宏只在被支持时才被定义。

扩展为所有其他FE_ *的按位OR的宏常量FE_ALL_EXCEPT始终定义，如果实现不支持浮点异常，则该常量将为零。

常量

说明

FE_DIVBYZERO

极点错误发生在较早的浮点运算中

FE_INEXACT

不精确的结果：舍入对于存储较早浮点运算的结果是必要的

FE_INVALID

在早期的浮点操作中发生域错误

FE_OVERFLOW

较早浮点运算的结果太大而无法表示

FE_UNDERFLOW

早期浮点运算的结果是低于正常的，并且精度下降

FE_ALL_EXCEPT

按位或所有受支持的浮点异常

该实现可以在<fenv.h>中定义附加的宏常量来标识附加的浮点异常。 所有这些常量都以FE_开头，后跟至少一个大写字母。

有关更多详细信息，请参阅math_errhandling。

例

#include <stdio.h>#include <math.h>#include <float.h>#include <fenv.h>
 #pragma STDC FENV_ACCESS ONvoid show_fe_exceptions(void){    printf("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");    feclearexcept(FE_ALL_EXCEPT);    printf("\n");}
 int main(void){    printf("MATH_ERREXCEPT is %s\n",
           math_errhandling & MATH_ERREXCEPT ? "set" : "not set"); 
    printf("0.0/0.0 = %f\n", 0.0/0.0);    show_fe_exceptions(); 
    printf("1.0/0.0 = %f\n", 1.0/0.0);    show_fe_exceptions(); 
    printf("1.0/10.0 = %f\n", 1.0/10.0);    show_fe_exceptions(); 
    printf("sqrt(-1) = %f\n", sqrt(-1));    show_fe_exceptions(); 
    printf("DBL_MAX*2.0 = %f\n", DBL_MAX*2.0);    show_fe_exceptions(); 
    printf("nextafter(DBL_MIN/pow(2.0,52),0.0) = %.1f\n",                      nextafter(DBL_MIN/pow(2.0,52),0.0));    show_fe_exceptions();}

可能的输出：

MATH_ERREXCEPT is set0.0/0.0 = nan
exceptions raised: FE_INVALID1.0/0.0 = inf
exceptions raised: FE_DIVBYZERO1.0/10.0 = 0.100000exceptions raised: FE_INEXACTsqrt(-1) = -nan
exceptions raised: FE_INVALID
DBL_MAX*2.0 = inf
exceptions raised: FE_INEXACT FE_OVERFLOWnextafter(DBL_MIN/pow(2.0,52),0.0) = 0.0exceptions raised: FE_INEXACT FE_UNDERFLOW

参考

  • C11标准（ISO / IEC 9899：2011）：

    • 7.6 / 6浮点环境<fenv.h>（p：207）

  • C99标准（ISO / IEC 9899：1999）：

    • 7.6 / 5浮点环境<fenv.h>（p：188）

扩展内容

math_errhandlingMATH_ERRNOMATH_ERREXCEPT（C99）（C99）（C99）

定义了常用数学函数（宏常量）使用的错误处理机制，

| 用于浮点异常宏的C ++文档 |

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