What is the error in using fopen instead of fopen_s as suggested by Visual Studio?

Question

I started working on the OpenGL code for Amusement Park. but I'm getting the following error:

"error C4996: 'fopen': This function or variable may be unsafe. Consider using fopen_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS. See online help for details."

even if I try to change it frm fopen to fopen_s, there more errors.

This is the code part:

GLuint LoadBMP(const char *fileName)
{
    FILE *file;
    unsigned char header[54], *data;
    unsigned int dataPos, size, width, height;
    file = fopen(fileName, "rb");
    fread(header, 1, 54, file);             //Windows BMP begin with 54 byte header
    dataPos = *(int*)&(header[0x0A]);   //dec10, Actual BMP data
    size = *(int*)&(header[0x22]);  //dec34, BMP Size
    width = *(int*)&(header[0x12]); //dec18, Image Width
    height = *(int*)&(header[0x16]);    //dec22, Image Height
    if (size == NULL)
        size = width * height * 3;
    if (dataPos == NULL)
        dataPos = 54;
    data = new unsigned char[size];
    fread(data, 1, size, file);
    fclose(file);
    GLuint texture;
    glGenTextures(1, &texture);             //Generate (allocate) 1 texture name
    glBindTexture(GL_TEXTURE_2D, texture);  //Bind the 2D texture

    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);  //MAG filter
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);  //MIN filter

    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_BGR_EXT, GL_UNSIGNED_BYTE, data); //target, level, internalFormat, width, height,border, format, type, data 
    return texture;
}

I'm getting error in the file = fopen statement.

Help me to find the error in this.

There's nothing wrong with that line of code. Apparently you're using some compiler setting that turns warnings into errors, which in turn lets Microsoft's paranoia control how you write code. — Pete Becker, Apr 01 '17 at 15:19
2 choices: (1) define the macro as show in the error message; or (2) show us the error you get with `fopen_s` (note it takes different parameters and returns an error code). — Richard Critten, Apr 01 '17 at 15:19
Before starting to use the `*_s` functions in C++ you might want to consider [C document N1967](http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1967.htm) proposing its removal from the next C standard. — Bo Persson, Apr 01 '17 at 19:39
*`fopen_s` is C11* No, `fopen_s` is from the **optional** Annex K of the C11 standard. Effectively that has only been implemented by Microsoft - but their implementation doesn't comply with the standards set in Annex K. So using Microsoft's "safer" functions is doubly non-portable: no one else implemented them, and Microsoft didn't meet the standard anyway. — Andrew Henle, Oct 23 '19 at 16:00

HDJEMAI · Answer 1 · 2017-04-01T15:31:06.703

1

fopen_s is the secure version of fopen so if you don't want to use fopen_s consider using _CRT_SECURE_NO_WARNINGS to get rid of that error, since you are using Visual Studio.

Now if you want to use fopen_s to correct the error, you have to look at the documentation of fopen_s

Example of use:

errno_t returnValue = fopen_s(&file, fileName, "r");

edited Apr 01 '17 at 15:31

answered Apr 01 '17 at 15:23

HDJEMAI

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It's probably more accurate to say `fopen_s()` is a part of Microsoft's attempt to [embrace, extend, and extinguish](https://en.wikipedia.org/wiki/Embrace,_extend,_and_extinguish) portable C code (those are Microsoft's own terms for how to take over a market...). Using `fopen_s()` does not make your code more secure, but it does make your code less portable. See [**N1967 - Field Experience With Annex K — Bounds Checking Interfaces**](http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1967.htm) – Andrew Henle Mar 22 '21 at 18:35

What is the error in using fopen instead of fopen_s as suggested by Visual Studio?

1 Answers1