CWE Rule 910

This issue occurs when a function operates on a stream that you closed earlier in your code.

The standard states that the value of a FILE* pointer is indeterminate after you close the stream associated with it. Operations using the FILE* pointer can produce unintended results.

One possible fix is to close the stream only at the end of operations. Another fix is to reopen the stream before using it again.

#include <stdio.h>

void func(void) {
    FILE *fp;
    void *ptr;

    fp = fopen("tmp","w");
    if(fp != NULL) {
        fclose(fp);
        fprintf(fp,"text");  //Noncompliant
    }
}

In this example, fclose closes the stream associated with fp. When you use fprintf on fp after fclose, the Use of previously closed resource defect appears.

One possible correction is to reverse the order of the fprintf and fclose operations.

#include <stdio.h>

void func(void) {
    FILE *fp;
    void *ptr;

    fp = fopen("tmp","w");
    if(fp != NULL) {
        fprintf(fp,"text");
        fclose(fp);
    }
}