assert

Syntax

#define NDEBUG #include <assert.h> assert(expression); assertval(expression);

Description

These macros are used to assist in debugging. The source code includes references to assert or assertval, passing them expressions that should be true (non-zero). When the expression yields false (zero), a diagnostic message is printed to the standard error stream, and the program aborts.

If you define the macro NDEBUG before including `assert.h', then these assert and assertval expand to nothing to reduce code size after debugging is done.

Return Value

assert returns 1 if its argument is non-zero, else it aborts.

assertval returns the value of its expression argument, if non-zero, else it aborts.

Portability

ANSI/ISO C	C89; C99 (see note 1)
POSIX	1003.2-1992; 1003.1-2001 (see note 2)

Notes:

1. assert is ANSI, assertval is not.
2. assert is Posix, assertval is not.

Example

/* Like `strdup', but doesn't crash if the argument is NULL. */ char * safe_strdup(const char *s) { assert(s != 0); return strdup(s); }