C4996 c ошибка fopen

Many of Microsoft’s secure functions, including fopen_s(), are part of C11, so they should be portable now. You should realize that the secure functions differ in exception behaviors and sometimes in return values. Additionally you need to be aware that while these functions are standardized, it’s an optional part of the standard (Annex K) that at least glibc (default on Linux) and FreeBSD’s libc don’t implement.

However, I fought this problem for a few years. I posted a larger set of conversion macros here., For your immediate problem, put the following code in an include file, and include it in your source code:

#pragma once
#if !defined(FCN_S_MACROS_H)
   #define   FCN_S_MACROS_H

   #include <cstdio>
   #include <string> // Need this for _stricmp
   using namespace std;

   // _MSC_VER = 1400 is MSVC 2005. _MSC_VER = 1600 (MSVC 2010) was the current
   // value when I wrote (some of) these macros.

   #if (defined(_MSC_VER) && (_MSC_VER >= 1400) )

      inline extern
      FILE*   fcnSMacro_fopen_s(char *fname, char *mode)
      {  FILE *fptr;
         fopen_s(&fptr, fname, mode);
         return fptr;
      }
      #define fopen(fname, mode)            fcnSMacro_fopen_s((fname), (mode))

   #else
      #define fopen_s(fp, fmt, mode)        *(fp)=fopen( (fmt), (mode))

   #endif //_MSC_VER

#endif // FCN_S_MACROS_H

Of course this approach does not implement the expected exception behavior.

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  • Fopen giving error

Fopen giving error

void In(void) //read the image
{
int i, j;
double el;
char buff[255];
stream = fopen(«test.txt», «r»); //skeltonize -> newedg.txt & normal myFile1
for (j = 0; j < ny; j++) //row
for (i = 0; i < nx; i++) //col
{
fscanf(stream, «%lf», &el);
I[i][j] = el;
}
fclose(stream);
}

This is the aspect of the code and this is the error i get:

Error C4996 ‘fopen’: This function or variable may be unsafe. Consider using fopen_s instead.

Error C4996 ‘fscanf’: This function or variable may be unsafe. Consider using fscanf_s instead.

If you are using Visual Studio you can #define _CRT_SECURE_NO_WARNINGS before your #include files.

Not recommended. It is using a bomb to swat a fly. And doesn’t fix the problems with the functions, you can still have buffer overruns.

OR

Use C11’s fopen_s() and fscanf_s() function that was created to prevent buffer overruns. As suggested in the error messages.

https://en.cppreference.com/w/c/io/fopen
https://en.cppreference.com/w/c/io/fopen

Still not working. Any other solution

Don’t use C code. Write C++ instead. Something like this should do it, assuming I is an array of some sensible type.

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ifstream inputFile("test.txt");
for (j = 0; j < ny; j++) //row
{
  for (i = 0; i < nx; i++) //col
  {
    inputFile >>  I[i][j];
  }
}

Last edited on

You should check if and why fopen fails.

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stream = fopen("test.txt", "r"); 
if (stream == NULL)
{
  perror(NULL); // #include <stdio.h>
  return;
}

Topic archived. No new replies allowed.

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Error C4996: ‘Fopen’: This Function Or Variable May Be Unsafe With Code Examples

In this lesson, we’ll use programming to attempt to solve the Error C4996: ‘Fopen’: This Function Or Variable May Be Unsafe puzzle. This is demonstrated by the code below.

Select your project and click "Properties".
then chose "Configuration Properties" -> "C/C++" -> "Preprocessor"
In the field "PreprocessorDefinitions" add ;_CRT_SECURE_NO_WARNINGS

As we have seen, the Error C4996: ‘Fopen’: This Function Or Variable May Be Unsafe problem was solved by using a number of different instances.

How do I fix C4244 warning?

If you get C4244, you should either change your program to use compatible types, or add some logic to your code, to ensure that the range of possible values will always be compatible with the types you are using.03-Aug-2021

How do I turn off errors in Visual Studio?

Suppress specific warnings for Visual C# or F# Or, select the project node and press Alt+Enter. Choose Build, and go to the Errors and warnings subsection. In the Suppress warnings or Suppress specific warnings box, specify the error codes of the warnings that you want to suppress, separated by semicolons.13-Jun-2022

What does #define _crt_secure_no_warnings do?

_CRT_SECURE_NO_WARNINGS means you don’t want the compiler to suggest the secure versions of the library functions, e.g. scanf_s when you use scanf .16-Jan-2020

How do you ignore warnings in C++?

To disable a set of warnings for a given piece of code, you have to start with a “push” pre-processor instruction, then with a disabling instruction for each of the warning you want to suppress, and finish with a “pop” pre-processor instruction.30-Aug-2019

How do I enable Errors in Visual Studio?

Simply, go to settings by using ctrl + comma . Search for Error squiggles . Enable it or select EnabledIfIncludesResolve . Then click on Modified on Workspace , if it is disabled, then enable it.13-Jun-2020

How do you ignore Errors in VS code?

To ignore all errors in the current file Press Alt+Enter.

How do you ignore a warning in VS code?

If you want to hide a particular warning code across your entire project, open the overall properties through the Project | Properties menu command, and when the properties appear, select the Build page. The Suppress Warnings box on that page accepts a semicolon-delimited list of codes.10-Sept-2017

How do I fix error C4996?

To fix a C4996 issue, we usually recommend you change your code.To turn off the warning for an entire project in the Visual Studio IDE:

  • Open the Property Pages dialog for your project.
  • Select the Configuration Properties > C/C++ > Advanced property page.
  • Edit the Disable Specific Warnings property to add 4996 .

How do I add CRT secure no warnings in Visual Studio?

Right Click ‘Project Properties->C/C+±>Preprocessor’ Add ‘_CRT_SECURE_NO_WARNINGS’ to preprocessor Definitions and click ok. In addition, if you have any other issue, please create a new feedback to us! Thanks&Regards.03-Sept-2019

What is an undefined reference unresolved external symbol error and how do I fix it?

So when we try to assign it a value in the main function, the linker doesn’t find the symbol and may result in an “unresolved external symbol” or “undefined reference”. The way to fix this error is to explicitly scope the variable using ‘::’ outside the main before using it.07-Aug-2022

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fopen deprecated warning
On Visual Studio 2015 C++ compiler, I get the following warning when my code uses the fopen and such calls.

foo.cpp(5) : warning C4996: ‘fopen’ was declared deprecated

        c:\program files\microsoft visual studio 8\vc\include\stdio.h(234) : see declaration of ‘fopen’

        Message: ‘This function or variable may be unsafe. Consider using fopen_s instead. To disable deprecation, use _CRT_SECURE_NO_DEPRECATE. See online help for details.’

Answer:

Well, you could add a:

#pragma warning (disable : 4996)

Before you are possible to use fopen but become you considered using fopen_s as the warning recommends? It returns an error code permitting you to check the result of the function call.

The problem with just disabling deprecated function warnings is that Microsoft may discard the role in question in a later version of the CRT, breaking your code. Now, this won’t happen in this instance with fopen because it’s part of the C & C++ ISO standards.

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See more:

error C4996: 'fopen': This function or variable may be unsafe. Consider using fopen_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS   
#include "stdafx.h"
#include<stdio.h>
#include<stdlib.h>
#include<string.h>

#include "IInvFile.h"
namespace SearchEngine_Project {
// Integrated Inverted Index (see lecture notes on Implementation)
IInvFile InvFile4;

int main3() {
        char tmp[10000];
        char str[1000];
        int docid;
        int loc;
        int cnt=0;
        FILE * fp = fopen("C:/Users/user/Documents/Visual Studio 2012/Projects/new4/const.txt", "rb");
        if (fp == NULL) {
                printf("Cannot open file \r\n");
                return 1;
                }

        // Initialize the Hash Table
        InvFile4.MakeHashTable(13023973);

        while(fgets(tmp,10000,fp) != NULL) {
                // Get the stem, the document identifier and the location
                sscanf(tmp,"%s %d %d", &(str[0]), &docid, &loc);

                // Add posting into the Integrated Inverted index
                // See lecture notes on Implementation
                InvFile4.Add(str, docid, 1);

                // Keep us informed about the progress
                cnt++;
                if ((cnt % 100000) == 0) printf("Added [%d]\r\n",cnt);
        }

        printf("Saving inverted file ...\r\n");
        InvFile4.Save("InvFile.txt");

        InvFile4.Clear();
        fclose(fp);
        return 0;
}
}

Updated 18-Dec-13 23:01pm

Comments

1 solution

Solution 1

The warning message is quite explicit:
«‘fopen’: This function or variable may be unsafe. Consider using fopen_s instead.»

See here: http://msdn.microsoft.com/en-us/library/ttcz0bys.aspx[^]

What it means is that fopen is not recommended for new code, as it may be removed from future version, having been superceeded by a newer, better version — in this case fopen_s

Either use the more modern equivalent as it suggests, or disable the warning (I’d go with the first option, myself)

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