Barry Smith <[email protected]> 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.