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


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    <h1 id="firstHeading" class="firstHeading">fegetenv, fesetenv</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 fegetenv( fenv_t* envp );</pre>
</td> <td> (1) </td> <td> <span class="t-mark-rev t-since-c99">(since C99)</span> </td> </tr> <tr class="t-dcl t-since-c99"> <td> <pre data-language="c">int fesetenv( const fenv_t* envp );</pre>
</td> <td> (2) </td> <td> <span class="t-mark-rev t-since-c99">(since C99)</span> </td> </tr>  </table> <p>1) Attempts to store the status of the floating-point environment in the object pointed to by <code>envp</code>.</p>
<p>2) Attempts to establish the floating-point environment from the object pointed to by <code>envp</code>. The value of that object must be previously obtained by a call to <code><a href="feholdexcept" title="c/numeric/fenv/feholdexcept">feholdexcept</a></code> or <code>fegetenv</code> or be a floating-point macro constant. If any of the floating-point status flags are set in <code>envp</code>, they become set in the environment (and are then testable with <code><a href="fetestexcept" title="c/numeric/fenv/fetestexcept">fetestexcept</a></code>), but the corresponding floating-point exceptions are not raised (execution continues uninterrupted)</p>
<h3 id="Parameters"> Parameters</h3> <table class="t-par-begin"> <tr class="t-par"> <td> envp </td> <td> - </td> <td> pointer to the object of type <code>fenv_t</code> which holds the status of the floating-point environment </td>
</tr>
</table> <h3 id="Return_value"> Return value</h3> <p><code>0</code> on success, non-zero otherwise.</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;
 
#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()) {
           case FE_TONEAREST:  printf ("FE_TONEAREST");  break;
           case FE_DOWNWARD:   printf ("FE_DOWNWARD");   break;
           case FE_UPWARD:     printf ("FE_UPWARD");     break;
           case FE_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 -&gt; %+4.1f\n", rint(+11.5)); /* midway between two integers */
    printf("+12.5 -&gt; %+4.1f\n", rint(+12.5)); /* midway between two integers */
    show_fe_environment();
    printf("\n");
 
    /* Save current environment. */
    rtn = fegetenv(&amp;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 -&gt; %+4.1f\n", rint(+11.5));
    printf("+12.5 -&gt; %+4.1f\n", rint(+12.5));
    show_fe_environment();
    printf("\n");
 
    /* Restore previous environment. */
    rtn = fesetenv(&amp;curr_env);
    show_fe_environment();
 
    return 0;
}</pre></div> <p>Output:</p>
<div class="text source-text"><pre data-language="c">current exceptions raised: none
current rounding method:   FE_TONEAREST
 
+11.5 -&gt; +12.0
+12.5 -&gt; +12.0
current exceptions raised: FE_INEXACT
current rounding method:   FE_TONEAREST
 
1.0/0.0 = inf
+11.5 -&gt; +11.0
+12.5 -&gt; +12.0
current exceptions raised: FE_DIVBYZERO FE_INEXACT
current rounding method:   FE_DOWNWARD
 
current exceptions raised: FE_INEXACT
current rounding method:   FE_TONEAREST</pre></div> </div> <h3 id="References"> References</h3>  <ul>
<li> C11 standard (ISO/IEC 9899:2011): </li>
<ul>
<li> 7.6.4.1 The fegetenv function (p: 213) </li>
<li> 7.6.4.3 The fesetenv function (p: 214) </li>
</ul>
<li> C99 standard (ISO/IEC 9899:1999): </li>
<ul>
<li> 7.6.4.1 The fegetenv function (p: 194) </li>
<li> 7.6.4.3 The fesetenv function (p: 195) </li>
</ul>
</ul>        <h3 id="See_also"> See also</h3> <table class="t-dsc-begin"> <tr class="t-dsc"> <td> <div><a href="feholdexcept" title="c/numeric/fenv/feholdexcept"> <span class="t-lines"><span>feholdexcept</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> saves the environment, clears all status flags and ignores all future errors <br> <span class="t-mark">(function)</span>  </td>
</tr> <tr class="t-dsc"> <td> <div><a href="feupdateenv" title="c/numeric/fenv/feupdateenv"> <span class="t-lines"><span>feupdateenv</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> restores the floating-point environment and raises the previously raise exceptions <br> <span class="t-mark">(function)</span>  </td>
</tr> <tr class="t-dsc"> <td> <div><a href="fe_dfl_env" title="c/numeric/fenv/FE DFL ENV"> <span class="t-lines"><span>FE_DFL_ENV</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> default floating-point environment <br> <span class="t-mark">(macro constant)</span>  </td>
</tr> <tr class="t-dsc"> <td colspan="2"> <span><a href="https://en.cppreference.com/w/cpp/numeric/fenv/feenv" title="cpp/numeric/fenv/feenv">C++ documentation</a></span> for <code>fegetenv, fesetenv</code> </td>
</tr> </table>           <div class="_attribution">
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