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# assert

From cppreference.com
< c‎ | error

Defined in header `<assert.h>` |  |
#ifdef NDEBUG #define assert(condition) ((void)0) #else #define assert(condition) /*implementation defined*/ #endif |  |

The definition of the macro `assert` depends on another macro, NDEBUG, which is not defined by the standard library.

If NDEBUG is defined as a macro name at the point in the source code where `<assert.h>` is included, then `assert` does nothing.

If NDEBUG is not defined, then `assert` checks if its argument (which must have scalar type) compares equal to zero. If it does, `assert` outputs implementation-specific diagnostic information on the standard error output and calls abort(). The diagnostic information is required to include the text of `expression`, as well as the values of the standard macros __FILE__, __LINE__, and the standard variable __func__.

### [edit] Parameters

condition | - | expression of scalar type

### [edit] Return value

(none)

### [edit] Example

Run this code

    #include <stdio.h>
    #include <assert.h>

    int main (int argc, char **argv)
    {
    	// Test if 0 is really equivalent to 0
    	assert (0 == 0);

    	// Test if 1 is different than 0...
    	assert (1 == 0);

    	return 0;
    }

Output:

    example: ex.c:10: int main(int, char**): Assertion `1 == 0' failed.
    Aborted

### [edit] See also

abort | causes abnormal program termination (without cleaning up) (function) [edit]

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