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

[Barry Smith]

  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.

  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
> ============
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