ASSERT(3)                            BSD                             ASSERT(3)



NAME
     assert - verify program assertion

SYNOPSIS
     #include <assert.h>

     void assert(expression)
     int expression;

DESCRIPTION
     This macro is useful for putting diagnostics into programs.  assert
     indicates that expression is expected to be true (non-zero) at this point
     in the program.  It causes an abort(3) with a diagnostic comment on the
     standard error output when expression is false (0).  The diagnostic
     comment includes the text of expression, the source file name, and the
     source line number.

     If the name NDEBUG is defined previous to including assert.h, either by
     compiling with the cc(1) option -DNDEBUG or using the #define
     preprocessor directive, assert calls are effectively deleted from the
     program [assert is defined to evaluate to (void(0))].

NOTES
     If _CLASSIC_ASSERT is defined, assert.h will declare the _assert
     function, rather than __assert function (and assert will evaluate to an
     _assert call).  This violates ANSI C requirements for application
     reserved names, but provides compatibility with typical common C library
     naming.  There are no semantic differences; _assert is a wrapper for
     __assert.

     Defining _CLASSIC_TYPES causes _CLASSIC_ASSERT to be defined.

DIAGNOSTICS
     "Assertion failed: file f line n." f is the source file and n the source
     line number of the assert statement.

SEE ALSO
     cpp(1), abort(3).

CAVEAT
     Since assert is implemented as a macro, the expression may not contain
     any string literals.