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assert

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Revision as of 04:53, 4 April 2014 by D41D8CD98F (Talk | contribs)

 
 
 
 
Defined in header <cassert>
#ifdef NDEBUG

#define assert(condition) ((void)0)
#else
#define assert(condition) /*implementation defined*/

#endif

The definition of the macro assert depends on another macro, NDEBUG, which is not defined by the standard library.

If NDEBUG is defined as a macro name at the point in the source code where <cassert> is included, then assert does nothing.

If NDEBUG is not defined, then assert checks if its argument (which must have scalar type) compares equal to zero. If it does, assert outputs implementation-specific diagnostic information on the standard error output and calls std::abort. The diagnostic information is required to include the text of expression, as well as the values of the standard macros __FILE__, __LINE__, and the standard variable __func__.

Contents

Parameters

condition - expression of scalar type

Return value

(none)

Example

#include <iostream>
// uncomment to disable assert()
// #define NDEBUG
#include <cassert>
 
int main()
{
    assert(2+2==4);
    std::cout << "Execution continues past the first assert\n";
    assert(2+2==5);
    std::cout << "Execution continues past the second assert\n";
}

Possible output:

Execution continues past the first assert
test: test.cc:10: int main(): Assertion `2+2==5' failed.
Aborted

See also

static assertion performs compile-time assertion checking (since C++11) [edit]
causes abnormal program termination (without cleaning up)
(function) [edit]