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| <h2 class="chapter">3 Reentrancy Properties of <code>libm</code></h2> |
| |
| <p><a name="index-reentrancy-198"></a><a name="index-g_t_0040code_007bmatherr_007d-and-reentrancy-199"></a>When a libm function detects an exceptional case, <code>errno</code> may be |
| set, the <code>matherr</code> function may be called, and a error message |
| may be written to the standard error stream. This behavior may not |
| be reentrant. |
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| <!-- The exact behavior depends on the currently selected error handling --> |
| <!-- mode (IEEE, POSIX, X/Open, or SVID). --> |
| <p>With reentrant C libraries like the Red Hat newlib C library, <code>errno</code> is |
| a macro which expands to the per-thread error value. This makes it thread |
| safe. |
| |
| <p>When the user provides his own <code>matherr</code> function it must be |
| reentrant for the math library as a whole to be reentrant. |
| |
| <p>In normal debugged programs, there are usually no math subroutine |
| errors—and therefore no assignments to <code>errno</code> and no <code>matherr</code> |
| calls; in that situation, the math functions behave reentrantly. |
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