Avoid having unreachable code

When having unreachable code it allows programs to be vulnerable to attacks and threat, as discovered by  [Watanabe, Akiyama, Kanei, Shioji, Takata, Sun, Ishi, Shibahara, Yagi, Mori, 2017].

Thus when creating new libraries or functions...

1. Be wary when using and placement of statements such as break, continue, and return, as they're indicators that segments of code are at risk of being unreachable; as stated by [Goel, Diaz-Agudo, Roth-Berghofer, 2016] .  
   1. Use Structured Programming, explained by [Joyner 2013], to help better the design of code therefore reducing the unnecessary use of break and continue; 
      
      
2. Modularize code as much as possible rather than combining methods/methods/classes/etc. into one.
   1.  [Chou, Chang, Kuo 2011]  explains why this is an issue in their paper; they state ...
      "In order to support design reuse, a circuit may have multiple modes and configurations so that it can be used in different applications. When verifying a specific configuration, a substantial amount of unused code may be discovered because the code may be written for other modes."
      
      
      
3. Avoiding putting in dead code, such as empty function or placeholders, an issue stated by [Chou, Chang, Kuo 2011]. If dead code is temporarily used as place holder, remove before release of app.

Noncompliant Code Example

This noncompliant code example shows an a line of code that is unreachable. 

int x = 1;
 
if (x == 1){
	return x;
	x += 1;  
}

The statement following the return statement will never get executed thus created errors and bugs in the program which rely on that statement.

Compliant Solution

In this compliant solution with reachable code.

int x = 1;

if (x == 1){
	x += 1;
	return x; 
}

Exceptions

Risk Assessment

Summary of risk assessment.

Automated Detection

Tools are available online, such as ProGuard, that help clean up code by removing unused statements that may have been a result of unreachable code.

Related Guidelines

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Bibliography