[previous] 2863 [next] Suspicious: Implementation-defined value resulting from left shift operation on expression of signed type.
Shift operations

Dataflow analysis has identified a code construct which is suspicious. The code may be entirely safe but further investigation is advisable.

A left shift operation is being performed on a signed integer expression and examination of the immediate context suggests that the result of this operation could sometimes be implementation-defined.

The result of a left shift operation will probably be meaningless when the value of the left hand operand is negative or when it is positive and of a magnitude such that the sign bit may be set by the shift operation.

This will happen in the example below unless the parameter 'n' is greater than 0. 


/*PRQA S 295,502,1253,1277,1279,2017,2982,2983,2984,2986,3120,3198,3199,3203,3227,3408,4131 ++*/

void foo(int n)
{
   long sl = 0x10000000L;
   long slr;
   int  i;

   for (i = 0; i < n; ++i)
   {
      sl = sl >> 1;
   }

   slr = sl << 2;              /*      */
   slr = sl << 3;              /* 2863 */
   slr = sl << 4;              /* 2863 */
}

No MISRA C:2012 Rules applicable to message 2863

See also:

QA·C Source Code Analyser 8.1
MISRA C:2012 Compliance Module 1.0
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