devdocs/c/numeric%2Ffenv%2Ffetestexcept.html


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    <h1 id="firstHeading" class="firstHeading">fetestexcept</h1>            <table class="t-dcl-begin"> <tr class="t-dsc-header"> <th> Defined in header <code>&lt;fenv.h&gt;</code> </th> <th> </th> <th> </th> </tr> <tr class="t-dcl t-since-c99"> <td> <pre data-language="c">int fetestexcept( int excepts );</pre>
</td> <td class="t-dcl-nopad"> </td> <td> <span class="t-mark-rev t-since-c99">(since C99)</span> </td> </tr>  </table> <p>Determines which of the specified subset of the floating-point exceptions are currently set. The argument <code>excepts</code> is a bitwise OR of the <a href="fe_exceptions" title="c/numeric/fenv/FE exceptions">floating-point exception macros</a>.</p>
<h3 id="Parameters"> Parameters</h3> <table class="t-par-begin"> <tr class="t-par"> <td> excepts </td> <td> - </td> <td> bitmask listing the exception flags to test </td>
</tr>
</table> <h3 id="Return_value"> Return value</h3> <p>Bitwise OR of the floating-point exception macros that are both included in <code>excepts</code> and correspond to floating-point exceptions currently set.</p>
<h3 id="Example"> Example</h3> <div class="t-example"> <div class="c source-c"><pre data-language="c">#include &lt;stdio.h&gt;
#include &lt;math.h&gt;
#include &lt;fenv.h&gt;
#include &lt;float.h&gt;
 
#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");
}
 
int main(void)
{
    /* Show default set of exception flags. */
    show_fe_exceptions();
 
    /* Perform some computations which raise exceptions. */
    printf("1.0/0.0     = %f\n", 1.0/0.0);        /* FE_DIVBYZERO            */
    printf("1.0/10.0    = %f\n", 1.0/10.0);       /* FE_INEXACT              */
    printf("sqrt(-1)    = %f\n", sqrt(-1));       /* FE_INVALID              */
    printf("DBL_MAX*2.0 = %f\n", DBL_MAX*2.0);    /* FE_INEXACT FE_OVERFLOW  */
    printf("nextafter(DBL_MIN/pow(2.0,52),0.0) = %.1f\n",
           nextafter(DBL_MIN/pow(2.0,52),0.0));   /* FE_INEXACT FE_UNDERFLOW */
    show_fe_exceptions();
 
    return 0;
}</pre></div> <p>Output:</p>
<div class="text source-text"><pre data-language="c">current exceptions raised:  none
1.0/0.0     = inf
1.0/10.0    = 0.100000
sqrt(-1)    = -nan
DBL_MAX*2.0 = inf
nextafter(DBL_MIN/pow(2.0,52),0.0) = 0.0
current exceptions raised:  FE_DIVBYZERO FE_INEXACT FE_INVALID FE_OVERFLOW FE_UNDERFLOW</pre></div> </div> <h3 id="References"> References</h3>  <ul>
<li> C11 standard (ISO/IEC 9899:2011): </li>
<ul><li> 7.6.2.5 The fetestexcept function (p: 211-212) </li></ul>
<li> C99 standard (ISO/IEC 9899:1999): </li>
<ul><li> 7.6.2.5 The fetestexcept function (p: 192-193) </li></ul>
</ul>      <h3 id="See_also"> See also</h3> <table class="t-dsc-begin"> <tr class="t-dsc"> <td> <div><a href="feclearexcept" title="c/numeric/fenv/feclearexcept"> <span class="t-lines"><span>feclearexcept</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-c99">(C99)</span></span></span></div> </td> <td> clears the specified floating-point status flags <br> <span class="t-mark">(function)</span>  </td>
</tr> <tr class="t-dsc"> <td colspan="2"> <span><a href="https://en.cppreference.com/w/cpp/numeric/fenv/fetestexcept" title="cpp/numeric/fenv/fetestexcept">C++ documentation</a></span> for <code>fetestexcept</code> </td>
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