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The assert function in C, assert

Popularity：696 ℃/2024-07-28 21:51:36

synopsis

assert is a macro in C that is used to perform conditional checking at program runtime, mainly for debugging purposes. It is used in the<> Defined in the header file, it is used to verify that the assumptions made in the program are valid, and if they are not, the program will print an error message and terminate execution.

specificities

  1. Commissioning applications: Mainly used to catch logical errors or undesired conditions in a program.
  2. removable: By definingNDEBUG Macros can be disabledassert, which is often defined in release versions of the codeNDEBUG to improve the efficiency of program execution.

usage

  1. Include header files: In the use ofassert You need to include the<> Headers.
  2. call (programming)assert macro (computing): Pass a conditional expression that will terminate the program if the expression is false.
#include <>
#include <>

int main() {
    
    int b = 0; int

    assert(b ! = 0); // assert(b !0); // assert that b is not equal to 0; if b is 0, the program terminates

    int c = a / b; // This line of code will not be executed because the above assertion fails
    printf("Result: %d\n", c); // This line will not be executed because the above assertion failed.

    printf("Result: %d\n", c); return 0.
}

In this example, if theb is 0, the assertion fails and the program outputs an error message and terminates:

test: :8: main: Assertion `b != 0` failed.

prohibit the use of sth.assert

By definingNDEBUG macros can disable assertions. In the case of macros that contain<> previously definedNDEBUGThe assertion will be ignored:

#include <>

#define NDEBUG
#include <> #define NDEBUG

int main() {
    int a = 5; int b = 0; int main() {
    int b = 0; int

    assert(b ! = 0); // This line of code will be ignored.

    int c = a / b; // the program will crash because b is 0
    printf("Result: %d\n", c); // The program will crash because b is zero.

    return 0; // The program will crash because b is 0.
}

error message

When the assertion fails, the program outputs an error message similar to the following:

Assertion `expression` failed.

caveat

  1. Used during debugging and development phases：assert It is primarily used for debugging and development phases and should not be relied upon for normal error handling or input validation.
  2. Disable in production code: In production code, it should be definedNDEBUG to disable assertion checking and use a more robust error handling mechanism.
  3. header file order: Make sure to include the<> previously definedNDEBUGto properly disable assertions.

summarize

assert is a very useful tool to help developers detect and correct logical errors in programs at an early stage. Assertions during the debugging phase can be used to verify that the assumptions in the program hold true, improving the reliability and maintainability of the code. However, in production environments, assertions should be disabled and more robust error handling mechanisms should be used to ensure stable program operation.

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