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 <dalc...@gmail.com> wrote: > > On 14 April 2015 at 02:46, Matthew Knepley <knep...@gmail.com> wrote: >> On Mon, Apr 13, 2015 at 5:48 PM, Barry Smith <bsm...@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
