C4996 c ошибка scanf

I have created a small application to find max number by using user-defined function with parameter. When I run it, it shows this message

Error 1 error C4996: ‘scanf’: This function or variable may be unsafe.
Consider using scanf_s instead. To disable deprecation, use
_CRT_SECURE_NO_WARNINGS. See online help for details.

What do I do to resolve this?

This is my code

#include<stdio.h>

void findtwonumber(void);
void findthreenumber(void);

int main() {
    int n;
    printf("Fine Maximum of two numbern");
    printf("Fine Maximum of three numbern");

    printf("Choose one:");
    scanf("%d", &n);
    if (n == 1)
    {
        findtwonumber();
    }
    else if (n == 2)
    {
        findthreenumber();
    }
    return 0;
}

void findtwonumber(void)
{
    int a, b, max;
    printf("Enter a:");
    scanf("%d", &a);
    printf("Enter b:");
    scanf("%d", &b);
    if (a>b)
        max = a;
    else
        max = b;
    printf("The max is=%d", max);
}

void findthreenumber(void)
{
    int a, b, c, max;
    printf("Enter a:");
    scanf("%d", &a);
    printf("Enter b:");
    scanf("%d", &b);
    printf("Enter c:");
    scanf("%d", &c);
    if (a>b)
        max = a;
    else if (b>c)
        max = b;
    else if (c>a)
        max = c;
    printf("The max is=%d", max);
}

2 Августа 2017

Время чтения: 5 минут

#include "stdafx.h"
#include <stdio.h>

int main() {
	int a, b;

	printf("Enter a: ");
	scanf("%d", &a);

	printf("Enter b: ");
	scanf("%d", &b);

	printf("a: %d, b: %dn", a, b);
	return 0;
}

Under the VS compiler, c4996 warning or error feedback information may appear when debugging and compiling C language programs written in the VS compiler. Here are a few based on my own practical experience. Can solve such problems. The following is described by a specific example.

Problem instance

The following shows a simple code `:

int main()
{
	int age = 0;
	printf("Please enter your age:>");
	scanf("%d",&age);
	printf("The age you entered is: %dn",age);
	return 0;
}

Error or warning prompt during debugging operation:

1>------  Build started:  project: test,  Configuration: Debug Win32 ------
1>  test.c
1>h:2020c c++Learnclasscodetesttesttest.c(24): error C4996: 'scanf': This function or variable may be unsafe. Consider using scanf_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS. See online help for details.
1>  c:program files (x86)windows kits10include10.0.10150.0ucrtstdio.h(1270): note:  See "scanf" statement
==========  generate:  Success 0  Failed 1  Newest 0  Skip 0  A ==========

The prompt said that replacing scanf with scanf_s can solve the problem, so according to the prompt, replace scanf in the code with scanf_s. The result after debugging is:

1>------ Build started:  project: test,  Configuration: Debug Win32 ------
1>  test.c
1>  test.vcxproj -> H:2020C C++LearnClassCodetestDebugtest.exe
==========  generate:  Success 1  Failed 0  Newest 0  Skip 0  A ==========

It can be seen that this method can indeed solve the problem.
However, in fact, scanf is a function provided by the C language to prevent the use of most compilers, and the scanf_s function is only a version provided by the VS compiler that it considers safe. It may not be applicable to other compilers and is not recommended.

Solution

method 1

Mentioned in the error message:

To disable deprecation, use _CRT_SECURE_NO_WARNINGS.

Therefore, add a line of code to the very beginning of the source program (before the header file):

#define _CRT_SECURE_NO_WARNINGS 1 

After debugging and compiling, the problem is solved:

1>------  Build started:  project: test,  Configuration: Debug Win32 ------
1>  test.c
1>  test.vcxproj -> H:2020C C++LearnClassCodetestDebugtest.exe
==========  generate:  Success 1  Failed 0  Newest 0  Skip 0  A ==========

In order to avoid adding the above-mentioned line of code every time you write a program, the following provides a method to automatically generate the above-mentioned line of code from the source file generated by the creation and addition:
The path of visual studio installed by yourself———>Find Microsoft Visual Studio 14.0 and click——->Click VC——- —>Click vcprojectitems————>Right-click new++file.cpp and open it with Notepad++———>Add #define _CRT_SECURE_NO_WARNINGS 1 to the file and save . In the future, the newly created **.c file can only show the above code, which can solve the problem of scanf, strcpy, strcat and other functions warnings or errors in c4996.

Method 2

Similar to method 1, adding the following line of code before the header file can also solve the problem:

#pragma warning(distable:4996) 

If you want the above line of code to appear automatically in the newly created .c file, please refer to the method procedure in Method 1.