assert
| Defined in header <cassert>
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| #ifdef NDEBUG #define assert(condition) ((void)0) |
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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__.
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The expression
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(since C++17) |
Contents |
[edit] Parameters
| condition | - | expression of scalar type |
[edit] Return value
(none)
[edit] Notes
Because assert is a function-like macro, commas anywhere in condition that are not protected by parentheses are interpreted as macro argument separators. Such commas are often found in template argument lists:
assert(std::is_same_v<int, int>); // error: assert does not take two arguments assert((std::is_same_v<int, int>)); // OK: one argument static_assert(std::is_same_v<int, int>); // OK: not a macro
[edit] Example
Possible output:
Execution continues past the first assert test: test.cc:10: int main(): Assertion `2+2==5' failed. Aborted
[edit] See also
| static assertion | performs compile-time assertion checking (since C++11) |
| causes abnormal program termination (without cleaning up) (function) | |
| C documentation for assert
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