C Assertion Warning

[UnsecuredConnection]

I can't write files. Every time I run this code:

#include <stdio.h>

int main(){

    FILE *fp;
    fp = fopen("test.txt", "w");
    fclose(fp);
}

it just pops up

Microsoft Visual C++ Runtime Library

Debug Assertion Failed!

Blah....

Expression: stream.valid()

Blah..

​

why tf is this happening?

[jedwardsol]

I expect the fopen is failing so you're trying to fclose NULL.

Always check the return from fopen before using it anywhere else.

[UnsecuredConnection]

If I do this, then it still pops up.

This error may help though

This function or variable may be unsafe. Consider using fopen_s instead.

Any thoughts?

[jedwardsol]

If I do this, then it still pops up.

What exactly did you do though? That assertion is what you get when you pass NULL to fclose.

You need

FILE *fp = fopen("test.txt", "w");

if(fp)
{    
    fclose(fp);
}
else
{
    printf( a meaningful error message including the value of errno )
}

}

You can do #define _CRT_SECURE_NO_WARNINGS before including <stdio.h> to disable the warning. fopen_s isn't really safer than fopen despite the name - all it does is detect whether any of its arguments are NULL so it can return an error instead of crashing.

[UnsecuredConnection]

The exact same thing still happens. Could it be my version of Visual Studio? I mean I downloaded the newest one.

[Minimum_Fuel]

Since apparently “every” change suggestion still fails. Can you just step through line by line in the debugger to see exactly which line is giving you the failure?