CWE Rule 772

This issue occurs when you open a file stream by using a FILE pointer but do not close it before:

If you do not release file handles explicitly as soon as possible, a failure can occur due to exhaustion of resources.

Close a FILE pointer before the end of its scope, or before you assign the pointer to another stream.

#include <stdio.h>

void func1( void ) {
    FILE *fp1;
    fp1 = fopen ( "data1.txt", "w" );
    fprintf ( fp1, "*" );

    fp1 = fopen ( "data2.txt", "w" ); //Noncompliant: previous stream still open
    fprintf ( fp1, "!" );
    fclose ( fp1 );
}

In this example, the file pointer fp1 is pointing to a file data1.txt. Before fp1 is explicitly dissociated from the file stream of data1.txt, it is used to access another file data2.txt. This is noncompliant because you are overwriting fp1 without closing the previous stream.

One possible correction is to explicitly dissociate fp1 from the file stream of data1.txt.

#include <stdio.h>

void func1( void ) {
    FILE *fp1;
    fp1 = fopen ( "data1.txt", "w" );
    fprintf ( fp1, "*" );
    fclose(fp1);

    fp1 = fopen ( "data2.txt", "w" );                  
    fprintf ( fp1, "!" );
    fclose ( fp1 );
}