== Why is this an issue?

Having a ``++switch++`` and its cases wholly encompassed by a control structure such as a ``++try++``, ``++@try++``, ``++catch++``, ``++@catch++``, or a loop is perfectly acceptable. (``++try++`` and ``++catch++`` are used hereafter to refer to both variants.) It is also acceptable to have a ``++goto++`` and its target label wholly encompassed in a control structure. 


What is not acceptable is using a ``++goto++`` or ``++case++`` to suddenly jump into the body of a ``++try++``, ``++catch++``, Objective-C ``++@finally++``, or loop structure. Tangling labels or ``++switch++`` blocks with other control structures results in code that is difficult, if not impossible to understand. More importantly, when it compiles (some of these constructs won't compile under ISO-conformant compilers), it can lead to unexpected results. Therefore this usage should be strictly avoided.


This {cpp} code sample, which is also applicable to Objective-C if ``++try++`` and ``++catch++`` are converted to ``++@try++`` and ``++@catch++``, demonstrates jumping into a ``++switch++`` and into a ``++try++`` and ``++catch++`` :


=== Noncompliant code example

[source,cpp]
----
void f ( int32_t i ) 
{ 
  if ( 10 == i ) 
  { 
    goto Label_10; // Noncompliant; goto transfers control into try block 
  }

  if ( 11 == i ) 
  { 
    goto Label_11; // Noncompliant; goto transfers control into catch block
  }

  switch ( i ) 
  { 
    case 1: 
      try 
      { 
        Label_10: 
        case 2:  // Noncompliant; switch transfers control into try block
          // Action 
          break; 
      }
      catch ( ... ) 
      { 
        Label_11: 
        case 3: // Noncompliant; switch transfers control into catch block
          // Action 
          break; 
      } 
      break;
    default: 
    { 
      // Default Action 
      break; 
    } 
  } 
}
----


=== Compliant solution

[source,cpp]
----
void f ( int32_t i ) 
{ 
  switch ( i ) 
  { 
    case 1: 
    case 2:
      // Action 
      break; 
    case 3:
      // Action 
      break; 
    case 10:

    default: 
    { 
      // Default Action 
      break; 
    } 
  } 

  try 
  {
    if ( 2 == i || 10 == i)
    {
      // Action
    }
  }
  catch ( ... )
  {
    if (3 == i || 11 == i)
    {
      // Action
    }
  }
}
----


== Resources

* MISRA {cpp}:2008, 15-0-3 - Control shall not be transferred into a try or catch block using goto or switch statement
* https://wiki.sei.cmu.edu/confluence/x/zdYxBQ[CERT, MSC20-C.] - Do not use a switch statement to transfer control into a complex block

ifdef::env-github,rspecator-view[]

'''
== Implementation Specification
(visible only on this page)

=== Message

\[Remove this use of "goto" to jump to the "xxx" label, which is located in a "[try|catch]" |

Extract this case from the "[try|catch|loop]" block because its switch is outside the block].


endif::env-github,rspecator-view[]
