CWE Rule 775

Missing Release of File Descriptor or Handle after Effective Lifetime

Since R2026a

Description

The product does not release a file descriptor or handle after its effective lifetime has ended, i.e., after the file descriptor/handle is no longer needed.

Polyspace Implementation

The rule checker checks for Resource leak.

Examples

Resource leak

Issue

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

• The end of the pointer's scope.

• Assigning the pointer to another stream.

Risk

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

Fix

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

Example — FILE Pointer Not Released Before End of Scope

#include <stdio.h>

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

    fp1 = fopen ( "data2.txt", "w" ); //Noncompliant
    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.

Correction — Release FILE Pointer

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 );
}

Check Information

Category: Others

PQL Name: std.cwe_native.R775

Version History

Introduced in R2026a