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<h1 id="firstHeading" class="firstHeading"><small>FE_DIVBYZERO, FE_INEXACT, FE_INVALID, FE_OVERFLOW, FE_UNDERFLOW, FE_ALL_EXCEPT</small></h1> <table class="t-dcl-begin"> <tr class="t-dsc-header"> <th> Defined in header <code><fenv.h></code> </th> <th> </th> <th> </th> </tr> <tr class="t-dcl t-since-c99"> <td> <pre data-language="c">#define FE_DIVBYZERO /*implementation defined power of 2*/</pre>
</td> <td class="t-dcl-nopad"> </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">#define FE_INEXACT /*implementation defined power of 2*/</pre>
</td> <td class="t-dcl-nopad"> </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">#define FE_INVALID /*implementation defined power of 2*/</pre>
</td> <td class="t-dcl-nopad"> </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">#define FE_OVERFLOW /*implementation defined power of 2*/</pre>
</td> <td class="t-dcl-nopad"> </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">#define FE_UNDERFLOW /*implementation defined power of 2*/</pre>
</td> <td class="t-dcl-nopad"> </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">#define FE_ALL_EXCEPT FE_DIVBYZERO | FE_INEXACT | \
FE_INVALID | FE_OVERFLOW | \
FE_UNDERFLOW</pre>
</td> <td class="t-dcl-nopad"> </td> <td> <span class="t-mark-rev t-since-c99">(since C99)</span> </td> </tr> </table> <p>All these macro constants (except <code>FE_ALL_EXCEPT</code>) expand to integer constant expressions that are distinct powers of 2, which uniquely identify all supported floating-point exceptions. Each macro is only defined if it is supported.</p>
<p>The macro constant <code>FE_ALL_EXCEPT</code>, which expands to the bitwise OR of all other <code>FE_*</code>, is always defined and is zero if floating-point exceptions are not supported by the implementation.</p>
<table class="t-dsc-begin"> <tr class="t-dsc-hitem"> <th> Constant </th> <th> Explanation </th>
</tr> <tr class="t-dsc"> <td> <code>FE_DIVBYZERO</code> </td> <td> pole error occurred in an earlier floating-point operation </td>
</tr> <tr class="t-dsc"> <td> <code>FE_INEXACT</code> </td> <td> inexact result: rounding was necessary to store the result of an earlier floating-point operation </td>
</tr> <tr class="t-dsc"> <td> <code>FE_INVALID</code> </td> <td> domain error occurred in an earlier floating-point operation </td>
</tr> <tr class="t-dsc"> <td> <code>FE_OVERFLOW</code> </td> <td> the result of an earlier floating-point operation was too large to be representable </td>
</tr> <tr class="t-dsc"> <td> <code>FE_UNDERFLOW</code> </td> <td> the result of an earlier floating-point operation was subnormal with a loss of precision </td>
</tr> <tr class="t-dsc"> <td> <code>FE_ALL_EXCEPT</code> </td> <td> bitwise OR of all supported floating-point exceptions </td>
</tr> </table> <p>The implementation may define additional macro constants in <code><fenv.h></code> to identify additional floating-point exceptions. All such constants begin with <code>FE_</code> followed by at least one uppercase letter.</p>
<p>See <a href="../math/math_errhandling" title="c/numeric/math/math errhandling">math_errhandling</a> for further details.</p>
<h3 id="Example"> Example</h3> <div class="t-example"> <div class="c source-c"><pre data-language="c">#include <stdio.h>
#include <math.h>
#include <float.h>
#include <fenv.h>
#pragma STDC FENV_ACCESS ON
void 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();
}</pre></div> <p>Possible output:</p>
<div class="text source-text"><pre data-language="c">MATH_ERREXCEPT is set
0.0/0.0 = nan
exceptions raised: FE_INVALID
1.0/0.0 = inf
exceptions raised: FE_DIVBYZERO
1.0/10.0 = 0.100000
exceptions raised: FE_INEXACT
sqrt(-1) = -nan
exceptions raised: FE_INVALID
DBL_MAX*2.0 = inf
exceptions raised: FE_INEXACT FE_OVERFLOW
nextafter(DBL_MIN/pow(2.0,52),0.0) = 0.0
exceptions raised: FE_INEXACT FE_UNDERFLOW</pre></div> </div> <h3 id="References"> References</h3> <ul>
<li> C11 standard (ISO/IEC 9899:2011): </li>
<ul><li> 7.6/6 Floating-point environment <fenv.h> (p: 207) </li></ul>
<li> C99 standard (ISO/IEC 9899:1999): </li>
<ul><li> 7.6/5 Floating-point environment <fenv.h> (p: 188) </li></ul>
</ul> <h3 id="See_also"> See also</h3> <table class="t-dsc-begin"> <tr class="t-dsc"> <td> <div><a href="../math/math_errhandling" title="c/numeric/math/math errhandling"> <span class="t-lines"><span>math_errhandling</span><span>MATH_ERRNO</span><span>MATH_ERREXCEPT</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-c99">(C99)</span></span><span><span class="t-mark-rev t-since-c99">(C99)</span></span><span><span class="t-mark-rev t-since-c99">(C99)</span></span></span></div> </td> <td> defines the error handling mechanism used by the common mathematical functions <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/FE_exceptions" title="cpp/numeric/fenv/FE exceptions">C++ documentation</a></span> for <span class=""><span>floating-point exception macros</span></span> </td>
</tr> </table> <div class="_attribution">
<p class="_attribution-p">
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<a href="https://en.cppreference.com/w/c/numeric/fenv/FE_exceptions" class="_attribution-link">https://en.cppreference.com/w/c/numeric/fenv/FE_exceptions</a>
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