[petsc-dev] clang --analyze messages on PETSc

[Matthew Knepley]

On Tue, Apr 14, 2015 at 5:11 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:

>
>   Jed suggested just passing requests for zero length malloc to malloc()
> and free() (claim is standards require them to behave properly  now a days)
> and remove all zero length checking from the macros. Will this resolve
> everything? Note that we need to pass a flag to --analyze telling it that
> zero length mallocs are ok otherwise it will generate some messages about
> them.
>

I really do not want that. I am especially unwilling to do that just to
appease static analysis.

  Matt


>   Barry
>
> > On Apr 14, 2015, at 3:33 AM, Lisandro Dalcin <dalcinl at gmail.com> wrote:
> >
> > On 14 April 2015 at 02:46, Matthew Knepley <knepley at gmail.com> wrote:
> >> On Mon, Apr 13, 2015 at 5:48 PM, Barry Smith <bsmith at mcs.anl.gov>
> wrote:
> >>>
> >>>
> >>> When I run clang --analyze on PETSc on getting warnings of the type
> below,
> >>> any idea how to deal with them? Clearly these things are usually not
> null
> >>> pointers or PETSc would crash everywhere.
> >>
> >>
> >> Lisandro brought this up.
> >>
> >> This is a problem with the analyzer. Anything that uses PetscMallocK()
> will
> >> be wrong since it can
> >> possibly be NULL. The limitations of static analysis are stark.
> >>
> >
> > There is a way to silent many of these false positives:
> >
> > 1) First we need to solve the differences between PetscMalloc() and
> > PetscMallocK() regarding zero-size allocations.
> > 2) PetscMalloc1() is by far the most used of all the PetscMallocK()
> > routines. So we should make PetscMalloc1() a direct call to
> > PetscMalloc() (no checks for zero-sized allocs) and modify
> > PetscMalloc() to handle zero-sized allocations by setting the pointer
> > to NULL.
> >
> > These simple changes will remove tons of "null pointer dereference"
> > false positives, and also fix the inconsistent behavior between
> > PetscMalloc() and PetscMallocK().
> >
> >
> > --
> > Lisandro Dalcin
> > ============
> > Research Scientist
> > Computer, Electrical and Mathematical Sciences & Engineering (CEMSE)
> > Numerical Porous Media Center (NumPor)
> > King Abdullah University of Science and Technology (KAUST)
> > http://numpor.kaust.edu.sa/
> >
> > 4700 King Abdullah University of Science and Technology
> > al-Khawarizmi Bldg (Bldg 1), Office # 4332
> > Thuwal 23955-6900, Kingdom of Saudi Arabia
> > http://www.kaust.edu.sa
> >
> > Office Phone: +966 12 808-0459
>
>


-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener
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