assert(3) Library Functions Manual assert(3)
NAME
assert - abort the program if assertion is false
LIBRARY
Standard C library (libc, -lc)
SYNOPSIS
#include <assert.h>
void assert(scalar expression);
DESCRIPTION
This macro can help programmers find bugs in their programs, or handle
exceptional cases via a crash that will produce limited debugging out-
put.
If expression is false (i.e., compares equal to zero), assert() prints
an error message to standard error and terminates the program by call-
ing abort(3). 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> was last in-
cluded, the macro assert() generates no code, and hence does nothing at
all. It is not recommended to define NDEBUG if using assert() to de-
tect error conditions since the software may behave non-deterministi-
cally.
RETURN VALUE
No value is returned.
ATTRIBUTES
For an explanation of the terms used in this section, see at-
tributes(7).
┌────────────────────────────────────────────┬───────────────┬─────────┐
│Interface │ Attribute │ Value │
├────────────────────────────────────────────┼───────────────┼─────────┤
│assert() │ Thread safety │ MT-Safe │
└────────────────────────────────────────────┴───────────────┴─────────┘
STANDARDS
POSIX.1-2001, POSIX.1-2008, C99.
BUGS
assert() is implemented as a macro; if the expression tested has side-
effects, program behavior will be different depending on whether NDEBUG
is defined. This may create Heisenbugs which go away when debugging is
turned on.
SEE ALSO
abort(3), assert_perror(3), exit(3)
Linux man-pages 6.03 2023-02-05 assert(3)
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