97 lines
2.4 KiB
Plaintext
97 lines
2.4 KiB
Plaintext
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.
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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.
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This C++ 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`` :
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== Noncompliant Code Example
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----
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void f ( int32_t i )
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{
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if ( 10 == i )
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{
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goto Label_10; // Noncompliant; goto transfers control into try block
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}
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if ( 11 == i )
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{
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goto Label_11; // Noncompliant; goto transfers control into catch block
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}
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switch ( i )
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{
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case 1:
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try
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{
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Label_10:
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case 2: // Noncompliant; switch transfers control into try block
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// Action
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break;
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}
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catch ( ... )
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{
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Label_11:
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case 3: // Noncompliant; switch transfers control into catch block
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// Action
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break;
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}
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break;
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default:
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{
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// Default Action
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break;
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}
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}
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}
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----
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== Compliant Solution
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----
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void f ( int32_t i )
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{
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switch ( i )
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{
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case 1:
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case 2:
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// Action
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break;
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case 3:
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// Action
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break;
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case 10:
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default:
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{
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// Default Action
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break;
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}
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}
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try
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{
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if ( 2 == i || 10 == i)
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{
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// Action
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}
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}
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catch ( ... )
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{
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if (3 == i || 11 == i)
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{
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// Action
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}
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}
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}
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----
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== See
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* MISRA C++:2008, 15-0-3 - Control shall not be transferred into a try or catch block using goto or switch statement
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* https://wiki.sei.cmu.edu/confluence/x/zdYxBQ[CERT, MSC20-C.] - Do not use a switch statement to transfer control into a complex block
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