On Tue, Apr 12, 2016 at 10:42:26PM -0500, Satish Balay wrote: > Ok - I see the bug in this code. > > static PetscErrorCode DMPlexReferenceTreeRestoreChildrenMatrices_Injection(DM > refTree, Mat inj, PetscScalar ****childrenMats) > > Since this funciton is defined as 'static' the compiler is doing > 'inter procedure analysis' across the calling function with -O [this > warning comes up only with -O build] > > 1. plextree.c:3506 has the following variable declared [uninitialized] > PetscScalar ***childrenMats; > > 2. the next usage of this variable is: plextree.c:3846 > ierr = > DMPlexReferenceTreeGetChildrenMatrices_Injection(refTree,injRef,&childrenMats);CHKERRQ(ierr); > > 3. Within this function - the first usage of this variable is plextree.c:L3453 > refPointFieldMats = *childrenMats; > > i.e access/use of uninitialized variable. > > The following supresses the warning - but there is clearly some lurking bug..
A bug in the code, or the analyzer? Like I said, there is a conditional-free path that leads to plextree.c:L3436 (was 3437)--- *childrenMats = refPointFieldMats; ---in the Get function before the line in the Restore function that's triggering the warning. Maybe the (shorter) Restore function is being inlined while the Get function isn't, I don't know, but I'm fairly confident this is a false positive. Furthermore, this code is covered by tests in next, but looking at the dashboard I don't see any warnings from the valgrind build. > > diff --git a/src/dm/impls/plex/plextree.c b/src/dm/impls/plex/plextree.c > index 2ee02d0..e51f704 100644 > --- a/src/dm/impls/plex/plextree.c > +++ b/src/dm/impls/plex/plextree.c > @@ -3503,7 +3503,7 @@ PetscErrorCode DMPlexComputeInjectorTree(DM coarse, DM > fine, PetscSF coarseToFin > PetscLayout rowMap, colMap; > PetscInt rowStart, rowEnd, colStart, colEnd, *nnzD, *nnzO; > PetscObject injRefObj; > - PetscScalar ***childrenMats; > + PetscScalar ***childrenMats=0; > PetscErrorCode ierr; > > PetscFunctionBegin; > > And this was introduced by http://bitbucket.org/petsc/petsc/commits/f30e825d > > Satish > > On Fri, 8 Apr 2016, Barry Smith wrote: > > > > > Toby, > > > > We'll be filtering out these false positives. It is just taking us a > > couple of days to determine that needs to be filtered. > > > > Barry > > > > > On Apr 8, 2016, at 2:36 PM, Tobin Isaac <[email protected]> wrote: > > > > > > > > > I spent a couple minutes verifying that there is no code path where > > > that variable is not initialized on line 3437. > > > > > > -Wmaybe-uninitialized seems to generate a lot of false positives. > > > Coupled with the blame digest's poor ability to assign blame, this > > > proactive approach seems to waste more time than a reactive > > > SEGV->valgrind->fix approach. > > > > > > Cheers, > > > Toby > > > > > > On Fri, Apr 08, 2016 at 02:12:22PM -0500, Satish Balay wrote: > > >> This should have been sent to Toby. > > >> > > >> I don't really understand the issue here. Its triggered by > > >> --with-debugging=0. I'm > > >> not sure why these compilers are pointing to petscsys.h. I get slightly > > >> different message > > >> on my laptop. > > >> > > >> mpicc -c -fPIC -Wall -Wwrite-strings -Wno-strict-aliasing > > >> -Wno-unknown-pragmas -fvisibility=hidden -g -O > > >> -I/home/balay/petsc/include > > >> -I/home/balay/petsc/arch-linux2-c-opt/include > > >> -I/home/balay/soft/mpich-3.1.4/include -MMD -MP > > >> /home/balay/petsc/src/dm/impls/plex/plextree.c -o > > >> arch-linux2-c-opt/obj/src/dm/impls/plex/plextree.o > > >> /home/balay/petsc/src/dm/impls/plex/plextree.c: In function > > >> ‘DMPlexComputeInjectorTree’: > > >> /home/balay/petsc/src/dm/impls/plex/plextree.c:3484:11: warning: > > >> ‘childrenMats’ may be used uninitialized in this function > > >> [-Wmaybe-uninitialized] > > >> ierr = PetscFree(refPointFieldMats);CHKERRQ(ierr); > > >> ^ > > >> /home/balay/petsc/src/dm/impls/plex/plextree.c:3507:18: note: > > >> ‘childrenMats’ was declared here > > >> PetscScalar ***childrenMats; > > >> ^ > > >> > > >> Satish > > >> > > >> On Fri, 8 Apr 2016, PETSc checkBuilds wrote: > > >> > > >>> > > >>> > > >>> Dear PETSc developer, > > >>> > > >>> This email contains listings of contributions attributed to you by > > >>> `git blame` that caused compiler errors or warnings in PETSc automated > > >>> testing. Follow the links to see the full log files. Please attempt to > > >>> fix > > >>> the issues promptly or let us know at [email protected] if you are > > >>> unable > > >>> to resolve the issues. > > >>> > > >>> Thanks, > > >>> The PETSc development team > > >>> > > >>> ---- > > >>> > > >>> warnings attributed to commit > > >>> https://bitbucket.org/petsc/petsc/commits/49d7da5 > > >>> PetscMalloc: allow ptr=malloc(0) and free(ptr) > > >>> > > >>> include/petscsys.h:1157 > > >>> > > >>> [http://ftp.mcs.anl.gov/pub/petsc/nightlylogs/archive/2016/04/08/build_next_arch-freebsd-cxx-pkgs-opt_wii.log] > > >>> /usr/home/balay/petsc.clone-2/include/petscsys.h:1157:88: warning: > > >>> 'childrenMats' may be used uninitialized in this function > > >>> [-Wmaybe-uninitialized] > > >>> > > >>> [http://ftp.mcs.anl.gov/pub/petsc/nightlylogs/archive/2016/04/08/build_next_arch-linux-opt-cxx-quad_grind.log] > > >>> /sandbox/petsc/petsc.clone-3/include/petscsys.h:1157:88: warning: > > >>> 'childrenMats' may be used uninitialized in this function > > >>> [-Wmaybe-uninitialized] > > >>> > > >>> [http://ftp.mcs.anl.gov/pub/petsc/nightlylogs/archive/2016/04/08/build_next_arch-freebsd-pkgs-opt_wii.log] > > >>> /usr/home/balay/petsc.clone/include/petscsys.h:1157:39: warning: > > >>> 'childrenMats' may be used uninitialized in this function > > >>> [-Wmaybe-uninitialized] > > >>> > > >>> [http://ftp.mcs.anl.gov/pub/petsc/nightlylogs/archive/2016/04/08/build_next_arch-linux-pkgs-latest_cg.log] > > >>> /sandbox/petsc/petsc.clone-4/include/petscsys.h:1157:25: warning: > > >>> 'childrenMats' may be used uninitialized in this function > > >>> [-Wmaybe-uninitialized] > > >>> > > >>> [http://ftp.mcs.anl.gov/pub/petsc/nightlylogs/archive/2016/04/08/build_next_arch-linux-pkgs-opt_crank.log] > > >>> /sandbox/petsc/petsc.clone/include/petscsys.h:1157:25: warning: > > >>> 'childrenMats' may be used uninitialized in this function > > >>> [-Wmaybe-uninitialized] > > >>> > > >>> ---- > > >>> To opt-out from receiving these messages - send a request to > > >>> [email protected]. > > >>> > > > > > > >
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