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Using the value of a pointer to a FILE object after the associated file is closed is undefined behavior. (See undefined behavior 148.) Programs that close the standard streams (especially stdout but also stderr and stdin) must be careful not to use these streams in subsequent function calls, particularly those that implicitly operate on them (such as printf(), perror(), and getc()).

This rule can be generalized to other file representations.

Noncompliant Code Example

In this noncompliant code example, the stdout stream is used after it is closed:

#include <stdio.h>
 
int close_stdout(void) {
  if (fclose(stdout) == EOF) {
    return -1;
  }
 
  printf("stdout successfully closed.\n");
  return 0;
}

Compliant Solution

In this compliant solution, stdout is not used again after it is closed. This must remain true for the remainder of the program, or stdout must be assigned the address of an open file object. 

#include <stdio.h>
 
int close_stdout(void) {
  if (fclose(stdout) == EOF) {
    return -1;
  }

  fputs("stdout successfully closed.", stderr);
  return 0;
}

Risk Assessment

Using the value of a pointer to a FILE object after the associated file is closed is undefined behavior.

Rule

Severity

Likelihood

Remediation Cost

Priority

Level

FIO46-C

Medium

Unlikely

Medium

P4

L3

Automated Detection

Tool

Version

Checker

Description

CodeSonar
5.1p0
IO.UACUse after close
Compass/ROSE


Coverity
2017.07

USE_AFTER_FREE

Implemented
Klocwork
2018

SV.INCORRECT_RESOURCE_HANDLING.URH


LDRA tool suite
9.7.1

48 D

Partially implemented
Parasoft C/C++test
10.4.2
CERT_C-FIO46-a

Do not use resources that have been freed

Polyspace Bug Finder

R2019b

CERT C: Rule FIO46-C


Checks for use of previously closed resource (rule partially covered)

PRQA QA-C

9.5

2696, 2697, 2698
SonarQube C/C++ Plugin
3.11
S3588

Related Vulnerabilities

Search for vulnerabilities resulting from the violation of this rule on the CERT website.

Bibliography

[IEEE Std 1003.1:2013]XSH, System Interfaces, open
[ISO/IEC 9899:2011

Subclause 7.21.3, "Files"
Subclause 7.21.5.1, "The fclose Function"