Editing c/assert.h/assert

{{DISPLAYTITLE: assert macro - <assert.h> - C}}
{{Assert.h - C}}
The '''assert''' macro, which is part of <[[assert.h - C|assert.h]]> can be used to insert diagnostic tests into a program.

== Synopsis ==
<source lang="c">#include <assert.h>
void assert(scalar expression);</source>

== Description ==
When executed, if the expression is false (I.E. compares to zero), a diagnostic message is printed in an implementation-defined format to the standard error stream. Assert then calls the abort function.

The diagnostic message includes:

* The text of the argument
* The name of the source file ([[__FILE__ - C|__FILE__]])
* The source line number ([[__LINE__ - C|__LINE__]])
* The name of the enclosing function ([[__func__ - C|__func__]]) ([[C99]])

If '''NDEBUG''' is defined as a macro name prior to the inclusion of <[[assert.h - C|assert.h]]>, assert gets defined as:

<source lang="c">#define assert(ignore) ((void)0)</source>

== Parameters ==
{| class="wikitable"
|-
! Parameter !! Description
|-
| expression || The expression to be evaluated
|}

== Returns ==
The assert macro returns no value.

== Example ==
<source lang="c">#include <assert.h>
#include <stdio.h>

int main(void)
{
    int i;

    for (i = 0; i < 10; i++)
    {
        printf("i = %d\n", i);
        assert(i < 5);
    }

    return 0;
}</source>

Example Output:

<pre>i = 0
i = 1
i = 2
i = 3
i = 4
i = 5
example: example.c:11: main: Assertion `i < 5' failed.
Aborted (core dumped)</pre>

Starting at variable i being set to zero, the loop continues until the assertion fails when i reaches 5. The program terminates by calling [[Stdlib.h/abort|abort()]] after printing the diagnostic message.

== See also ==
* [[Assert.h/static_assert - C|static_assert macro]]
* [[assert.h - C|<assert.h> header]]
* [[C standard library]]
* [[C Programming Language]]

{{DEFAULTSORT:assert - assert.h - C}}
[[Category:assert.h - C]]
[[Category:Assertion - C]]