CERT C: Rule SIG35-C

Do not return from a computational exception signal handler

expand all in page

Description

Rule Definition

Do not return from a computational exception signal handler.¹

Polyspace Implementation

The rule checker checks for Return from computational exception signal handler.

Examples

expand all

Return from computational exception signal handler

Issue

Return from computational exception signal handler occurs when a signal handler returns after catching a computational exception signal SIGFPE, SIGILL, or SIGSEGV.

Risk

A signal handler that returns normally from a computational exception is undefined behavior. Even if the handler attempts to fix the error that triggered the signal, the program can behave unexpectedly.

Fix

Check the validity of the values of your variables before the computation to avoid using a signal handler to catch exceptions. If you cannot avoid a handler to catch computation exception signals, call abort(), quick_exit(), or _Exit() in the handler to stop the program.

Example - Signal Handler Return from Division by Zero

#include <errno.h>
#include <limits.h>
#include <signal.h>
#include <stdlib.h>

static volatile sig_atomic_t denom;
/* Declare signal handler to catch division by zero 
computation error. */
void sig_handler(int s)
{
    int s0 = s;
    if (denom == 0)
    {
        denom = 1;
    }
	/* Normal return from computation exception
	signal */
    return;  //Noncompliant
}


long func(int v)
{
    denom = (sig_atomic_t)v;
       
        if (signal(SIGFPE, sig_handler) == SIG_ERR)
        {
            /* Handle error */
        }
		
	long result = 100 / (long)denom;
    return result;
}

In this example, sig_handler is declared to handle a division by zero computation error. The handler changes the value of denom if it is zero and returns, which is undefined behavior.

Correction — Call abort() to Terminate Program

After catching a computational exception, call abort() from sig_handler to exit the program without further error.

#include <errno.h>
#include <limits.h>
#include <signal.h>
#include <stdlib.h>

static volatile sig_atomic_t denom;
/* Declare signal handler to catch division by zero 
computation error. */

void sig_handler(int s)
{
    int s0 = s;
	/* call to abort() to exit the program */
    abort(); 
}

long func(int v)
{
    denom = (sig_atomic_t)v;
       
        if (signal(SIGFPE, sig_handler) == SIG_ERR)
        {
            /* Handle error */
        }
		
	long result = 100 / (long)denom;
    return result;
}

Check Information

Group: Rule 11. Signals (SIG)

Version History

Introduced in R2019a

¹ This software has been created by MathWorks incorporating portions of: the “SEI CERT-C Website,” © 2017 Carnegie Mellon University, the SEI CERT-C++ Web site © 2017 Carnegie Mellon University, ”SEI CERT C Coding Standard – Rules for Developing safe, Reliable and Secure systems – 2016 Edition,” © 2016 Carnegie Mellon University, and “SEI CERT C++ Coding Standard – Rules for Developing safe, Reliable and Secure systems in C++ – 2016 Edition” © 2016 Carnegie Mellon University, with special permission from its Software Engineering Institute.

ANY MATERIAL OF CARNEGIE MELLON UNIVERSITY AND/OR ITS SOFTWARE ENGINEERING INSTITUTE CONTAINED HEREIN IS FURNISHED ON AN "AS-IS" BASIS. CARNEGIE MELLON UNIVERSITY MAKES NO WARRANTIES OF ANY KIND, EITHER EXPRESSED OR IMPLIED, AS TO ANY MATTER INCLUDING, BUT NOT LIMITED TO, WARRANTY OF FITNESS FOR PURPOSE OR MERCHANTABILITY, EXCLUSIVITY, OR RESULTS OBTAINED FROM USE OF THE MATERIAL. CARNEGIE MELLON UNIVERSITY DOES NOT MAKE ANY WARRANTY OF ANY KIND WITH RESPECT TO FREEDOM FROM PATENT, TRADEMARK, OR COPYRIGHT INFRINGEMENT.

This software and associated documentation has not been reviewed nor is it endorsed by Carnegie Mellon University or its Software Engineering Institute.