NAME

assert — insert program diagnostics

SYNOPSIS

#include <assert.h>

void assert(scalar expression);


DESCRIPTION

^[CX] The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the requirements described here and the ISO C standard is unintentional. This volume of POSIX.1-2024 defers to the ISO C standard.

The assert() macro shall insert diagnostics into programs; it shall expand to a void expression. When it is executed, if expression (which shall have a scalar type) is false (that is, compares equal to 0), assert() shall write information about the particular call that failed on stderr and shall call abort().

The information written about the call that failed shall include the text of the argument, the name of the source file, the source file line number, and the name of the enclosing function; the latter are, respectively, the values of the preprocessing macros __FILE__ and __LINE__ and of the identifier __func__.

Forcing a definition of the name NDEBUG, either from the compiler command line or with the preprocessor control statement #define NDEBUG ahead of the #include <assert.h> statement, shall stop assertions from being compiled into the program.

RETURN VALUE

The assert() macro shall not return a value.

ERRORS

No errors are defined.

EXAMPLES

None.

APPLICATION USAGE

None.

RATIONALE

None.

FUTURE DIRECTIONS

None.

SEE ALSO

abort, stdin

XBD <assert.h>

CHANGE HISTORY

First released in Issue 1. Derived from Issue 1 of the SVID.

Issue 6

The prototype for the expression argument to assert() is changed from int to scalar for alignment with the ISO/IEC 9899:1999 standard.

The DESCRIPTION of assert() is updated for alignment with the ISO/IEC 9899:1999 standard.