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ASSERT(3) Library Functions Manual ASSERT(3)

assertexpression verification macro

#include <assert.h>

assert(expression);

The () macro tests the given expression and if it is false, the calling process is terminated. A diagnostic message is written to stderr and the function abort(3) is called, effectively terminating the program.

If expression is true, the () macro does nothing.

The () macro may be removed at compile time by defining NDEBUG as a macro (e.g., by using the cc(1) option -DNDEBUG).

The assertion:

assert(1 == 0);

generates a diagnostic message similar to the following:

Assertion failed: (1 == 0), function main, file assertion.c, line 100.

abort(3)

The assert() macro conforms to ISO/IEC 9899:1999 (“ISO C99”).

An assert macro appeared in Version 6 AT&T UNIX.

January 26, 1999 FreeBSD-11.1