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

[Lisandro Dalcin]

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)
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