Re: CINT crashes when reading 2 objects with identical key from 2 different files

Hi Thiemo,

Ha, interesting idea :-)

I'd recommend something different (more stable and faster), though. You can put your histograms into a struct inside your selector:

class MySelector ... {
...
struct Hists {
  TH1* fHist1;
  TH2* fHist2;
  ...
} fHists;
...
};

Now all you need to do in your selector's constructor is to (value) initialize that struct:

MySelector::MySelector(...): ..., fHists(), ... {...}

The empty set of parentheses after fHists tell the compiler to value initialize fHists. See the standard (8.5 [dcl.init]).

Cheers, Axel.

Thiemo Nagel wrote on 12/14/2011 11:40 AM:
> Dear Axel,
>
> great many thanks for taking the time to look into the matter! I'll be
> good and keep in mind to initialize all pointers. Now I know the source
> of the problem, I understand that the stacktrace is pointing in this
> direction:
>
> #13 0xb71e9c90 in TClass::Destructor(void*, bool) ()
> #14 0xb626a2d9 in TBufferFile::ReadFastArray()
> #15 0xb632b687 in int TStreamerInfo::ReadBuffer<char**>()
>
> Please allow me another question: To avoid this problem once and for
> all, I've tried to hack together an automatic initialisation like that:
>
> void
> GenericSelector::InitializeDataMembers() {
> TClass *cl = IsA();
> TList *l = cl->GetListOfDataMembers();
> TIter next( l );
> TObject *obj;
> while ( (obj = next()) ) {
> const TDataMember *member = dynamic_cast<TDataMember*>( obj );
> if ( member && member->IsaPointer() ) {
> TString type( member->GetFullTypeName() );
> if ( type.BeginsWith( "TH1" ) ) {
> char *ptr = (char*)this + member->GetOffset();
> *ptr = NULL;
> }
> }
> }
> }
>
> But it fails miserably. (Interestingly, the point of failure seems to
> be at the GetOffset() call, not at the access to *ptr.) Do I really
> need to create an accessor for every member or is there an easier way?
>
> Thank you and kind regards,
> Thiemo
>
>
>
> On 12/09/2011 02:58 PM, Axel Naumann wrote:

>> Some members were uninitialized. As you know, you can read data from a
>> TFile into an existing object (think "Event" in a TTree). And you can
>> re-read, into the same object. Reading the old object, ROOT might have
>> initialized the member TH2D* fBeamPdY_nocut by creating a histogram, and
>> having fBeamPdY_nocut point to it. Which means when reading the next
>> object it first needs to delete the histogram fBeamPdY_nocut points to.
>>
>> You happen to not initialize fBeamPdY_nocut in the constructor, which
>> means ROOT has no way of knowing that this was in fact not allocated.
>> Simply add initializers for the missing members.
>>
>> This is what I used to scan through your list of members:
>> $ grep -E '\*f[[:alnum:]_]+;' /build/tmp/Selector.h | sed -E
>> 's,^.*\*(f[[:alnum:]_]+);.*$,\1,' |sort>  Thiemo_vars.txt
>> $ grep -E '^ *f[[:alnum:]_]+ *\(' /build/tmp/Selector.h | sed -E 's,^
>> *(f[[:alnum:]_]+) *\(.*$,\1,' |sort>  Thiemo_init.txt
>> $ diff -u0 Thiemo_vars.txt Thiemo_init.txt |less
>>
>> "+" will be initializers for variables that are non-pointers (because
>> Thiemo_vars.txt only contains pointer vars). "-" will be the ones you
>> still need to initialize.
>>
>> Let us know if that didn't fix it.
>>
>> Cheers, Axel.
>>
>>
>> Thiemo Nagel wrote on 11/30/2011 06:18 PM:
>>> Dear ROOTers,
>>>
>>> I'd kindly ask for your help with some crashes that I'm observing with
>>> some of my code running with ROOT 5.30.03.  I guess that the problem is
>>> on my side, but I can't figure out what is wrong.
>>>
>>> Starting point:  I'm storing the output of my analysis in a customized
>>> "Selector" class which inherits from "MySelector" which inherits from
>>> TSelector.  To determine some physical quantities, I'd like to divide
>>> the output of two analysis runs, which means that I'm trying to read two
>>> Selector objects from two different .root files.  But this is already
>>> causing crashes.  (I've tested that both selectors work well, when the
>>> files are opened individually.  It's just when both are accessed in the
>>> same script that the problem occurs.)
>>>
>>> testpol.C is a minimal script which triggers my problem.
>>> prepareSelectors.C must be called beforehand in order to load all
>>> classes into CINT.  (For some reason, interpreting the class fails.)
>>> I've also attached MySelector.h and Selector.h, in case that might be
>>> useful for diagnosis.
>>>
>>> Any help would be greatly appreciated!
>>>
>>> Cheers,
>>> Thiemo
>>>
>>> P.S.:  Below is the output of one of the crashes:
>>>
>>> [0] mnemosyne:~/analysis/selector>  root -n prepareSelectors.C testpol.C
>>> root [0]
>>> Processing prepareSelectors.C...
>>> 0.177548 s
>>> 0.215103 s
>>> 0.243131 s
>>> 0.269481 s
>>> 0.295701 s
>>> 0.323266 s
>>> 0.35179 s
>>> 0.379835 s
>>> 0.408063 s
>>> 0.449982 s
>>> Processing testpol.C...
>>> TFile**         murd.root
>>>   TFile*         murd.root
>>>    KEY: Selector Selector;1
>>> got Selector: 'murd'
>>> TFile**         mumc.root
>>>   TFile*         mumc.root
>>>    KEY: Selector Selector;1
>>>
>>>   *** Break *** segmentation violation
>>>
>>>
>>>
>>> ===========================================================
>>> There was a crash.
>>> This is the entire stack trace of all threads:
>>> ===========================================================
>>> #0  0xb7779424 in __kernel_vsyscall ()
>>> #1  0xb65c9003 in __waitpid_nocancel ()
>>>      at ../sysdeps/unix/syscall-template.S:82
>>> #2  0xb656ae63 in do_system (line=<value optimized out>)
>>>      at ../sysdeps/posix/system.c:149
>>> #3  0xb66863bd in system (
>>>      line=0xb909630 "/usr/local/root/root_v5.30.03/etc/gdb-backtrace.sh
>>> 3137 1>&2") at pt-system.c:29
>>> #4  0xb72203cd in TUnixSystem::Exec(char const*) ()
>>>     from /usr/local/root/root_v5.30.03/lib/libCore.so.5.30
>>> #5  0xb722716b in TUnixSystem::StackTrace() ()
>>>     from /usr/local/root/root_v5.30.03/lib/libCore.so.5.30
>>> #6  0xb72259af in TUnixSystem::DispatchSignals(ESignals) ()
>>>     from /usr/local/root/root_v5.30.03/lib/libCore.so.5.30
>>> #7  0xb7225abd in ?? () from
>>> /usr/local/root/root_v5.30.03/lib/libCore.so.5.30
>>> #8  0xb721cdc2 in ?? () from
>>> /usr/local/root/root_v5.30.03/lib/libCore.so.5.30
>>> #9  0xb724bffd in textinput::TerminalConfigUnix::HandleSignal(int) ()
>>>     from /usr/local/root/root_v5.30.03/lib/libCore.so.5.30
>>> #10 0xb724c3d6 in ?? () from
>>> /usr/local/root/root_v5.30.03/lib/libCore.so.5.30
>>> #11<signal handler called>
>>> #12 0xb5a46c1d in ?? () from
>>> /usr/local/root/root_v5.30.03/lib/libHist.so.5.30
>>> #13 0xb71e9c90 in TClass::Destructor(void*, bool) ()
>>>     from /usr/local/root/root_v5.30.03/lib/libCore.so.5.30
>>> #14 0xb626a2d9 in TBufferFile::ReadFastArray(void**, TClass const*, int,
>>> bool, TMemberStreamer*, TClass const*) ()
>>>     from /usr/local/root/root_v5.30.03/lib/libRIO.so.5.30
>>> #15 0xb632b687 in int TStreamerInfo::ReadBuffer<char**>(TBuffer&, char**
>>> const&, int, int, int, int) () from
>>> /usr/local/root/root_v5.30.03/lib/libRIO.so.5.30
>>> #16 0xb62ae1a9 in TStreamerInfoActions::GenericAction(TBuffer&, void*,
>>> TStreamerInfoActions::TConfiguration const*) ()
>>>     from /usr/local/root/root_v5.30.03/lib/libRIO.so.5.30
>>> #17 0xb626439c in
>>> TBufferFile::ReadSequence(TStreamerInfoActions::TActionSequence const&,
>>> void*) () from /usr/local/root/root_v5.30.03/lib/libRIO.so.5.30
>>> #18 0xb626486b in TBufferFile::ReadClassBuffer(TClass const*, void*,
>>> TClass const*) () from /usr/local/root/root_v5.30.03/lib/libRIO.so.5.30
>>> #19 0xb44d674e in Selector::Streamer(TBuffer&) ()
>>>     from /tmp/tnagel/aclic_builddir/Selector_cc.so
>>> #20 0xb62a1afb in TKey::ReadObj() ()
>>>     from /usr/local/root/root_v5.30.03/lib/libRIO.so.5.30
>>> #21 0xb62751f1 in TDirectoryFile::Get(char const*) ()
>>>     from /usr/local/root/root_v5.30.03/lib/libRIO.so.5.30
>>> #22 0xb727159e in ?? () from
>>> /usr/local/root/root_v5.30.03/lib/libCore.so.5.30
>>> #23 0xb6a7f0f7 in Cint::G__ExceptionWrapper(int (*)(G__value*, char
>>> const*, G__param*, int), G__value*, char*, G__param*, int) ()
>>>     from /usr/local/root/root_v5.30.03/lib/libCint.so.5.30
>>> #24 0xb6b2e4cf in G__execute_call ()
>>>     from /usr/local/root/root_v5.30.03/lib/libCint.so.5.30
>>> #25 0xb6b2f36a in G__call_cppfunc ()
>>>     from /usr/local/root/root_v5.30.03/lib/libCint.so.5.30
>>> #26 0xb6b09991 in G__interpret_func ()
>>>     from /usr/local/root/root_v5.30.03/lib/libCint.so.5.30
>>> #27 0xb6af61ec in G__getfunction ()
>>>     from /usr/local/root/root_v5.30.03/lib/libCint.so.5.30
>>> #28 0xb6bf6524 in G__getstructmem(int, G__FastAllocString&, char*, int,
>>> char*, int*, G__var_array*, int) ()
>>>     from /usr/local/root/root_v5.30.03/lib/libCint.so.5.30
>>> #29 0xb6beafc5 in G__getvariable ()
>>>     from /usr/local/root/root_v5.30.03/lib/libCint.so.5.30
>>> #30 0xb6acfc18 in G__getitem ()
>>>     from /usr/local/root/root_v5.30.03/lib/libCint.so.5.30
>>> #31 0xb6ad51ac in G__getexpr ()
>>>     from /usr/local/root/root_v5.30.03/lib/libCint.so.5.30
>>> #32 0xb6af5694 in G__getfunction ()
>>>     from /usr/local/root/root_v5.30.03/lib/libCint.so.5.30
>>> #33 0xb6ad028b in G__getitem ()
>>>     from /usr/local/root/root_v5.30.03/lib/libCint.so.5.30
>>> #34 0xb6ad51ac in G__getexpr ()
>>>     from /usr/local/root/root_v5.30.03/lib/libCint.so.5.30
>>> #35 0xb6af6a6f in G__getfunction ()
>>>     from /usr/local/root/root_v5.30.03/lib/libCint.so.5.30
>>> #36 0xb6ad028b in G__getitem ()
>>>     from /usr/local/root/root_v5.30.03/lib/libCint.so.5.30
>>> #37 0xb6ad51ac in G__getexpr ()
>>>     from /usr/local/root/root_v5.30.03/lib/libCint.so.5.30
>>> #38 0xb6abf235 in G__define_var ()
>>>     from /usr/local/root/root_v5.30.03/lib/libCint.so.5.30
>>> #39 0xb6b5bc9c in G__exec_statement ()
>>>     from /usr/local/root/root_v5.30.03/lib/libCint.so.5.30
>>> #40 0xb6b0ac7e in G__interpret_func ()
>>>     from /usr/local/root/root_v5.30.03/lib/libCint.so.5.30
>>> #41 0xb6af6251 in G__getfunction ()
>>>     from /usr/local/root/root_v5.30.03/lib/libCint.so.5.30
>>> #42 0xb6ad028b in G__getitem ()
>>>     from /usr/local/root/root_v5.30.03/lib/libCint.so.5.30
>>> #43 0xb6ad51ac in G__getexpr ()
>>>     from /usr/local/root/root_v5.30.03/lib/libCint.so.5.30
>>> #44 0xb6adfe28 in G__calc_internal ()
>>>     from /usr/local/root/root_v5.30.03/lib/libCint.so.5.30
>>> #45 0xb6b6e629 in G__process_cmd ()
>>>     from /usr/local/root/root_v5.30.03/lib/libCint.so.5.30
>>> #46 0xb71de75b in TCint::ProcessLine(char const*,
>>> TInterpreter::EErrorCode*) ()
>>>     from /usr/local/root/root_v5.30.03/lib/libCore.so.5.30
>>> #47 0xb71dc111 in TCint::ProcessLineSynch(char const*,
>>> TInterpreter::EErrorCode*) () from
>>> /usr/local/root/root_v5.30.03/lib/libCore.so.5.30
>>> #48 0xb71253bc in TApplication::ExecuteFile(char const*, int*, bool) ()
>>>     from /usr/local/root/root_v5.30.03/lib/libCore.so.5.30
>>> #49 0xb71256dc in TApplication::ProcessFile(char const*, int*, bool) ()
>>>     from /usr/local/root/root_v5.30.03/lib/libCore.so.5.30
>>> #50 0xb7122ae8 in TApplication::ProcessLine(char const*, bool, int*) ()
>>>     from /usr/local/root/root_v5.30.03/lib/libCore.so.5.30
>>> #51 0xb68069ca in TRint::Run(bool) ()
>>>     from /usr/local/root/root_v5.30.03/lib/libRint.so.5.30
>>> #52 0x08048ebf in main ()
>>> ===========================================================
>>>
>>>
>>> The lines below might hint at the cause of the crash.
>>> If they do not help you then please submit a bug report at
>>> http://root.cern.ch/bugs. Please post the ENTIRE stack trace
>>> from above as an attachment in addition to anything else
>>> that might help us fixing this issue.
>>> ===========================================================
>>> #12 0xb5a46c1d in ?? () from
>>> /usr/local/root/root_v5.30.03/lib/libHist.so.5.30
>>> #13 0xb71e9c90 in TClass::Destructor(void*, bool) ()
>>>     from /usr/local/root/root_v5.30.03/lib/libCore.so.5.30
>>> #14 0xb626a2d9 in TBufferFile::ReadFastArray(void**, TClass const*, int,
>>> bool, TMemberStreamer*, TClass const*) ()
>>>     from /usr/local/root/root_v5.30.03/lib/libRIO.so.5.30
>>> #15 0xb632b687 in int TStreamerInfo::ReadBuffer<char**>(TBuffer&, char**
>>> const&, int, int, int, int) () from
>>> /usr/local/root/root_v5.30.03/lib/libRIO.so.5.30
>>> #16 0xb62ae1a9 in TStreamerInfoActions::GenericAction(TBuffer&, void*,
>>> TStreamerInfoActions::TConfiguration const*) ()
>>>     from /usr/local/root/root_v5.30.03/lib/libRIO.so.5.30
>>> #17 0xb626439c in
>>> TBufferFile::ReadSequence(TStreamerInfoActions::TActionSequence const&,
>>> void*) () from /usr/local/root/root_v5.30.03/lib/libRIO.so.5.30
>>> #18 0xb626486b in TBufferFile::ReadClassBuffer(TClass const*, void*,
>>> TClass const*) () from /usr/local/root/root_v5.30.03/lib/libRIO.so.5.30
>>> #19 0xb44d674e in Selector::Streamer(TBuffer&) ()
>>>     from /tmp/tnagel/aclic_builddir/Selector_cc.so
>>> #20 0xb62a1afb in TKey::ReadObj() ()
>>>     from /usr/local/root/root_v5.30.03/lib/libRIO.so.5.30
>>> #21 0xb62751f1 in TDirectoryFile::Get(char const*) ()
>>>     from /usr/local/root/root_v5.30.03/lib/libRIO.so.5.30
>>> #22 0xb727159e in ?? () from
>>> /usr/local/root/root_v5.30.03/lib/libCore.so.5.30
>>> ===========================================================
>>>
>>>
>>> Root>  Function testpol() busy flag cleared
>>>
>>>