@node assert, misc
@subheading Syntax

@example
#define NDEBUG
#include <assert.h>

assert(expression);
assertval(expression);
@end example

@subheading Description

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

If you define the macro @code{NDEBUG} before including @file{assert.h},
then the macros expand to nothing to reduce code size after debugging is
done.

@subheading Return Value

@code{assert} returns one if it passes, else it aborts.

@code{assertval} returns the value of the expression if nonzero, else it
aborts.

@subheading Portability

@port-note ansi @code{assert} is ANSI, @code{assertval} is not.
@port-note posix @code{assert} is Posix, @code{assertval} is not.
@portability ansi, posix

@subheading Example

@example
int strdup(char *s)
@{
  assert(s != 0);
@end example