catalogue

• 1, Introduction to assert function
• 2, The assert function uses
• 3, Usage Summary and precautions of assert function
• 4, Guess you like it

Zero foundation C/C + + learning route recommendation: C/C + + Learning directory >> Introduction to basic C language

1, Introduction to assert function

Assertions are familiar to everyone, and most programming languages also have the feature of assertions. Simply put, an assertion is a check on a hypothetical condition. assert macro prototype definition:

//Need to include header file < assert. H >
#include <assert.h>

/*
 Description: terminates program execution if its condition returns an error

 Parameters:
    expression : Conditional judgment or expression
 */

void assert( int expression );

assert The value of the expression will be checked to determine whether the executor needs to be terminated. That is, if the value of expression is false (i.e. 0), it will first print an error message to the standard error stream stderr, and then call abort Function to terminate program operation; Otherwise, assert has no effect.

2, The assert function uses

/******************************************************************************************/
//@Author: ape programming
//@Blog (personal blog address): www.codersrc.com
//@File:C language tutorial - C language assert function
//@Time:2021/07/18 07:30
//@Motto: no small steps can lead to thousands of miles. No small streams can lead to rivers and seas. The highlights of program life need to be accumulated unremittingly!
/******************************************************************************************/


#include <stdio.h>
#include <assert.h>
#include <stdlib.h>
int main( void )
{
    FILE *fp;

    fp = fopen( "456.txt", "w" );//Open a file in a writable manner. If it does not exist, create a file with the same name
    assert( fp );                           //So there will be no mistakes here
    fclose( fp );

    fp = fopen( "123.txt", "r" );//Open a file as read-only. If it does not exist, opening the file fails
    assert( fp );                           //So there's a mistake here
    fclose( fp );                           //The program will never run here
    return 0;
}

By default, assert Macros work only in the Debug version (internal Debug version) and will be ignored in the Release version (Release version).

3, Usage Summary and precautions of assert function

1. Use assert to verify the validity of the passed parameters at the beginning of the function

/******************************************************************************************/
//@Author: ape programming
//@Blog (personal blog address): www.codersrc.com
//@File:C language tutorial - C language assert function
//@Time:2021/07/18 07:30
//@Motto: no small steps can lead to thousands of miles. No small streams can lead to rivers and seas. The highlights of program life need to be accumulated unremittingly!
/******************************************************************************************/


int resetBufferSize(int nNewSize)
{
　　//Function: change buffer size,
　　//Parameter: nNewSize buffer length
　　//Return value: current length of buffer
　　//Note: keep the original information content unchanged. Nnewsize < = 0 means to clear the buffer
　　assert(nNewSize >= 0);
　　assert(nNewSize <= MAX_BUFFER_SIZE);
　　...
}

2. Each assert only checks one condition, because when multiple conditions are checked at the same time, if the assertion fails, it is impossible to intuitively judge which condition fails

/******************************************************************************************/
//@Author: ape programming
//@Blog (personal blog address): www.codersrc.com
//@File:C language tutorial - C language assert function
//@Time:2021/07/18 07:30
//@Motto: no small steps can lead to thousands of miles. No small streams can lead to rivers and seas. The highlights of program life need to be accumulated unremittingly!
/******************************************************************************************/


//Wrong writing
assert(a>=0 && b<=0 && c>0);

//Correct writing
assert(a>=0);
assert(b<=0);
assert(c>0);

3. assert The disadvantage is that frequent calls will greatly affect the performance of the program and increase additional overhead.

4, Guess you like it

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29. C language assert function

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