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| <h3 class="section">2.5 <code>assert</code>—macro for debugging diagnostics</h3> |
| |
| <p><a name="index-assert-6"></a><strong>Synopsis</strong> |
| <pre class="example"> #include <assert.h> |
| void assert(int <var>expression</var>); |
| |
| </pre> |
| <p><strong>Description</strong><br> |
| Use this macro to embed debuggging diagnostic statements in |
| your programs. The argument <var>expression</var> should be an |
| expression which evaluates to true (nonzero) when your program |
| is working as you intended. |
| |
| <p>When <var>expression</var> evaluates to false (zero), <code>assert</code> |
| calls <code>abort</code>, after first printing a message showing what |
| failed and where: |
| |
| <pre class="smallexample"> Assertion failed: <var>expression</var>, file <var>filename</var>, line <var>lineno</var>, function: <var>func</var> |
| </pre> |
| <p>If the name of the current function is not known (for example, |
| when using a C89 compiler that does not understand __func__), |
| the function location is omitted. |
| |
| <p>The macro is defined to permit you to turn off all uses of |
| <code>assert</code> at compile time by defining <code>NDEBUG</code> as a |
| preprocessor variable. If you do this, the <code>assert</code> macro |
| expands to |
| |
| <pre class="smallexample"> (void(0)) |
| </pre> |
| <p><br> |
| <strong>Returns</strong><br> |
| <code>assert</code> does not return a value. |
| |
| <p><br> |
| <strong>Portability</strong><br> |
| The <code>assert</code> macro is required by ANSI, as is the behavior |
| when <code>NDEBUG</code> is defined. |
| |
| <p>Supporting OS subroutines required (only if enabled): <code>close</code>, <code>fstat</code>, |
| <code>getpid</code>, <code>isatty</code>, <code>kill</code>, <code>lseek</code>, <code>read</code>, <code>sbrk</code>, <code>write</code>. |
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