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# assert

From cppreference.com
< cpp‎ | error

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__.

### [edit] Parameters

condition | - | expression of scalar type

### [edit] Return value

(none)

### [edit] Example

Run this code

    #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";
    }

Output:

    Execution continues past the first assert
    test: test.cc:8: int main(): Assertion `2+2==5' failed.
    Aborted

### [edit] See also

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

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