Hi ROOT'ers et al,
I'm experiencing a very strange error when I compile a class for
handling a ROOT file with a TTree in it. Basically the class opens a
TFile and creates a TTree in it.
On a single processor i386, running GNU/Linux (Redhat 6.2), using 2nd
level optimisation (-O2), ROOT 3.01/06, everything works fine.
On a dual processor i386, runnning GNU/Linux (Redhat 6.1), using the
same optimisation and ROOT version, the class crashed with SIGSEGV
after lines like:
fTree = new TTree("T","BRAT Event Tree");
fTree->SetAutoSave(5000000); // autosave when 5 Mbyte written
Running the program in the debugger says that the SIGSEGV comes from
0x413f509f in TTreePlayer::Scan ()
and a trace gives
#0 0x413f509f in TTreePlayer::Scan ()
from /afs/rhic/opt/brahms/new/lib/libTreePlayer.so
#1 0x40a20a91 in TTree::Scan ()
from /afs/rhic/opt/brahms/new/lib/libTree.so.3.01
#2 0x40dc86bf in BrEventIO::InitializeRootTreeFile ()
(BrEventIO is the class in question). Now, looking through the code,
I see absolutly no where where the message TTree::Scan is send. The
code continues like
BrEvent *dummy = new BrEvent("ev",0,0);
fBranch = fTree->Branch("event","BrEvent", &dummy,fBufsize,fSplit);
delete dummy;
Then I tried to compile the class in question on the SMP GNU/Linux
machine with only first level optimisation (-O1) and no optimisation,
and everything works smoothly.
I know the compiler on Redhat 6.1 is really old
gcc version egcs-2.91.66 19990314/Linux (egcs-1.1.2 release)
and probably a newer compiler will do the trick. However, that is not
an option in our case. Also, when I compiled ROOT I used the
linuxegcs configuration which also only has 1st level optimisation.
I searched ROOT talk for anything pertaining to the GCC optimisation,
but only found
http://root.cern.ch/cgi-bin/print_hit_bold.pl/root/roottalk/roottalk00/2581.html?Optimization#first_hit
which seems to be the same problem, but Rene's answer that didn't
really help much (quite understandable, since this is probably a very
compiler/os/machine specific thing).
So the question is: Has anyone else seen this? Does anyone know what
could be wrong?
And also: Heads up to those using Redhat 6.1 on an SMP machine!
Yours,
Christian -----------------------------------------------------------
Holm Christensen Phone: (+45) 35 35 96 91
Sankt Hansgade 23, 1. th. Office: (+45) 353 25 305
DK-2200 Copenhagen N Web: www.nbi.dk/~cholm
Denmark Email: cholm@nbi.dk
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