assert - abort the program if assertion is false
void assert(scalar expression);
This macro can help programmers find bugs in their programs, or handle
exceptional cases via a crash that will produce limited debugging output.
is false (i.e., compares equal to zero), assert
prints an error message to standard error and terminates the program by
. The error message includes the name of the file and
function containing the assert
() call, the source code line number of
the call, and the text of the argument; something like:
prog: some_file.c:16: some_func: Assertion `val == 0' failed.
If the macro NDEBUG
is defined at the moment <assert.h>
last included, the macro assert
() generates no code, and hence does
nothing at all. It is not recommended to define NDEBUG
() to detect error conditions since the software may behave
No value is returned.
For an explanation of the terms used in this section, see attributes(7)
POSIX.1-2001, POSIX.1-2008, C89, C99. In C89, expression
is required to
be of type int
and undefined behavior results if it is not, but in C99
it may have any scalar type.
() is implemented as a macro; if the expression tested has
side-effects, program behavior will be different depending on whether
is defined. This may create Heisenbugs which go away when
debugging is turned on.
This page is part of release 4.13 of the Linux man-pages
description of the project, information about reporting bugs, and the latest
version of this page, can be found at