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Manual Reference Pages  - ASSERT (3)

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assert - abort the program if assertion is false

CONTENTS

Synopsis
Description
Bugs

#include <assert.h> 



void assert(scalar expression); 

If the macro NDEBUG was defined at the moment <assert.h> was last included, the macro assert() generates no code, and hence does nothing at all. Otherwise, the macro assert() prints an error message to standard output and terminates the program by calling abort() if expression is false (i.e., compares equal to zero).

The purpose of this macro is to help the programmer find bugs in his program. The message "assertion failed in file foo.c, function do_bar(), line 1287" is of no help at all to a user.

No value is returned.

ISO9899 (ANSI C). In the 1990 standard, expression is required to be of type int and undefined behavior results if it is not, but in the 1999 standard it may have any scalar type.

assert() is implemented as a macro; if the expression tested has side-effects, program behaviour will be different depending on whether NDEBUG is defined. This may create Heisenbugs which go away when debugging is turned on.

exit(3), abort(3), assert_perror(3)

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