[petsc-dev] technical C question

[Jed Brown]

Barry Smith <bsmith at mcs.anl.gov> writes:
> the clang static code analyzer reports 
>
> In file included from /sandbox/petsc/petsc.clone/include/petsc/private/matimpl.h:1233:
> /sandbox/petsc/petsc.clone/include/petscbt.h:85:36: warning: The result of the '<<' expression is undefined
>           BT_mask       = (char)(1 << index%PETSC_BITS_PER_BYTE),
>                                  ~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> Is the code wrong/unnecessary or clang?

I would guess it is complaining about C99 §6.5.7.3:

  If the value of the right operand is negative or is greater than or
  equal to the width of the promoted left operand, the behavior is
  undefined.
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