I am having a little problem with the following macro:
{
gROOT->Reset();
gSystem->Load("libMyClasses.so");
TH1F dull("dull","dullhisto",100, -5, 5);
for(Int_t i=0; i<1000; i++){
dull.Fill( (gRandom->Gaus(1.5, .5)) );
}
cout<<"dull.GetMean(): "<<dull.GetMean()<<endl;
TFile f("test.root", "RECREATE");
MyClass mc;
mc.SetType("tester");
mc.SetTube(2);
mc.SetPixel(5);
mc.SetHist(dull);
cout<<"mc.GetMean(): "<<mc.GetMean()<<endl;
f.ls();
mc.Write();
f.ls();
f.Close();
}
The macro outputs:
root [0] .x test.C
dull.GetMean(): 1.47894
mc.GetMean(): 1.47894
TFile** test.root
TFile* test.root
OBJ: TH1F dull dullhisto : 0
TFile** test.root
TFile* test.root
OBJ: TH1F dull dullhisto : 0
KEY: MyClass MyClass;1
root [1] f.Close();
Fatal in <operator delete>: storage area overwritten
aborting
*ROOT crashes out at this point*
This result suprised me in two ways:
(1) Why is the TH1F "dull" added to the test.root directory? I would not
have expected this behaviour, considering that dull was created prior to
opening the TFile.
(2) I suspect the crash is due to (1). When the file closes, it writes
out dull, which invalidates it.
{See for reference the User's Guide p168. They use heap objects and
pointers there though.}
Also:
If I open a browser and access the TFile, A MyClass object is indeed in
there. This is what I expected. If I double click the MyClass object, it
pulls up the Object Inspector (ok). It also then shows a TH1F within the
right browser window (ok, wasn't sure what would happen). Further double
clicks on the MyClass object produce more histograms though! Why is this.
It is perhaps not disaster, but rather confusing to look at! They seem to
be clones of each other (rather than references to one object), since if I
smooth one of them, the others do not reflect the change when drawn. How
can I understand/get rid of this behaviour?
Some time ago a collegue told me that she always wrote compiled code
because macros often did unexpected things. I tend to find myself in the
same boat. As an observation, I notice that tutorials and the users
manual examples tend to feature much more dynamic allocation than I would
normally write. I don't really appreciate why this is, perhaps
it's only stylistic, but maybe I need to change my coding practices when
writing macros?
Comments greatly appreciated!
Mike Kordosky
--
Graduate Research Assistant // High Energy Physics Lab
kordosky@hep.utexas.edu // University of Texas at Austin
ph: (512) 471-8426 (RLM Lab, Office)
(512) 475-8673 (ENS Lab)
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