TCanvas::SaveAs() segfaults when histogram titles contain latex

DylanJW · January 16, 2019, 12:39pm

Hi all. I am having a problem where ROOT crashes when I try and save my TCanvas, provided that the histogram title uses any latex characters. This is especially strange for two reasons: it was working previously (I have tried running an old version of the code and found that it no longer works); and also my canvas is made up of two TPads, one for a TH1D and one for a TGraph, and the TGraph axis labels contain latex that draws just fine.

Some info: I have tried this both using ROOT 6.12/06 (on lxplus nodes) and 6.14/04 (on local machine, sourced from cvmfs).

Here is a pared-down version of the code for the function that is formatting & saving the figures:

void genProjectionHists_s::PlotProjection(TH1* hist_a, TH1* hist_b, const char* outputLocation, const char* figureTitle = "Title", const char* figureXLabel = "X-axis label") {
	// Sum weights
	hist_a->Sumw2();
	hist_b->Sumw2();
	
	// Scale histograms
	hist_a->Scale(1./hist_a->Integral());
	hist_b->Scale(1./hist_b->Integral());
	
	// Calculate residuals
	Double_t resVals[200];
	Double_t xVals[200];
	int numOfBins = hist_a->GetNbinsX();
	double Xmin = hist_a->GetXaxis()->GetXmin();
	double Xmax = hist_a->GetXaxis()->GetXmax();
	for (int i = 0; i < numOfBins; i++) {
		// calculate x position
		xVals[i] = Xmin + i*Xmax/numOfBins;
		// residuals: res[n] = (a[n] - b[n])/sqrt(err_a[n]^2 + err_b[n]^2)
		if (hist_a->GetBinContent(i+1) > 0 && hist_b->GetBinContent(i+1) > 0 && hist_a->GetBinError(i+1)+hist_b->GetBinError(i+1) > 0.) {
			resVals[i] = (hist_a->GetBinContent(i+1) - hist_b->GetBinContent(i+1))/sqrt(pow(hist_a->GetBinError(i+1),2) + pow(hist_b->GetBinError(i+1),2));
		}
	}
	
	// Create & format graph
	TGraph *gr = new TGraph(numOfBins, xVals, resVals);
	gr->SetTitle(""); // figure title goes to histogram, graph has no title
	gr->GetXaxis()->SetRangeUser(Xmin, Xmax);
	gr->GetXaxis()->SetTitle(figureXLabel);
	gr->GetXaxis()->SetTitleSize(.1);
	gr->GetXaxis()->SetLabelSize(.1);
	gr->GetYaxis()->SetTitle("Pulls");
	gr->GetYaxis()->SetTitleOffset(0.5);
	gr->GetYaxis()->SetTitleSize(.1);
	gr->GetYaxis()->SetLabelSize(.1);
	gr->SetFillColor(1);
	gr->SetMarkerStyle(21);
	
	// Format histograms
	hist_a->SetTitle(figureTitle);
	hist_a->GetXaxis()->SetLabelOffset(999);
	hist_a->GetXaxis()->SetLabelSize(0);
	hist_a->GetYaxis()->SetTitle("Events (normalised to 1)");
	hist_a->GetYaxis()->SetTitleOffset(1.4);
	hist_a->SetLineColor(kBlue);
	hist_b->SetLineColor(kRed);
	
	// Create canvas & pads
	TCanvas* canv = new TCanvas("canv", "", 1000, 1000);
	TPad *padh = new TPad("padh","",0.05,0.30,0.95,0.95,0); // histograms
	TPad *padr= new TPad("padr","",0.05,0.05,0.95,0.30,0); // residuals
	padh->SetBottomMargin(0.02);
	padr->SetTopMargin(0.);
	padr->SetBottomMargin(0.25);
	padr->SetTickx();
	padh->Draw();
	padr->Draw();
	
	// Draw to residuals pad
	padr->cd();
	gr->Draw("AB"); // draw residuals
	// Draw to histograms pad
	padh->cd();
	hist_a->Draw();
	hist_b->Draw("same");

	// Final formatting & output
	canv->SetLeftMargin(2.5); canv->SetRightMargin(2.5);
	std::string outputLocationStr(outputLocation);
	canv->SaveAs((outputLocationStr + ".pdf").c_str());
	canv->SaveAs((outputLocationStr + ".png").c_str());
	canv->SaveAs((outputLocationStr + ".C").c_str());
}

So it crashes whenever I pass it a figureTitle that contains latex (eg. “#pi”), although figureXLabel is able to handle latex just fine. Here is a copy of the error message produced:

 *** Break *** segmentation violation



===========================================================
There was a crash.
This is the entire stack trace of all threads:
===========================================================
#0  0x000000368b0ac89e in waitpid () from /lib64/libc.so.6
#1  0x000000368b03e4e9 in do_system () from /lib64/libc.so.6
#2  0x00007f6181f5febd in TUnixSystem::StackTrace() () from /cvmfs/sft.cern.ch/lcg/releases/ROOT/6.14.04-0d8dc/x86_64-slc6-gcc62-opt/lib/libCore.so
#3  0x00007f6181f62624 in TUnixSystem::DispatchSignals(ESignals) () from /cvmfs/sft.cern.ch/lcg/releases/ROOT/6.14.04-0d8dc/x86_64-slc6-gcc62-opt/lib/libCore.so
#4  <signal handler called>
#5  0x00007f6173e59ade in FT_Done_Glyph () from /cvmfs/sft.cern.ch/lcg/releases/LCG_94/freetype/2.6.3/x86_64-slc6-gcc62-opt/lib/libfreetype.so.6
#6  0x00007f61741c7191 in TTF::LayoutGlyphs() () from /cvmfs/sft.cern.ch/lcg/releases/ROOT/6.14.04-0d8dc/x86_64-slc6-gcc62-opt/lib/libGraf.so
#7  0x00007f61741c784f in TTF::GetTextExtent(unsigned int&, unsigned int&, char*) () from /cvmfs/sft.cern.ch/lcg/releases/ROOT/6.14.04-0d8dc/x86_64-slc6-gcc62-opt/lib/libGraf.so
#8  0x00007f61741916c4 in TLatex::Analyse(double, double, TLatex::TextSpec_t, char const*, int) () from /cvmfs/sft.cern.ch/lcg/releases/ROOT/6.14.04-0d8dc/x86_64-slc6-gcc62-opt/lib/libGraf.so
#9  0x00007f6174194271 in TLatex::Anal1(TLatex::TextSpec_t, char const*, int) () from /cvmfs/sft.cern.ch/lcg/releases/ROOT/6.14.04-0d8dc/x86_64-slc6-gcc62-opt/lib/libGraf.so
#10 0x00007f617418d1b7 in TLatex::Analyse(double, double, TLatex::TextSpec_t, char const*, int) () from /cvmfs/sft.cern.ch/lcg/releases/ROOT/6.14.04-0d8dc/x86_64-slc6-gcc62-opt/lib/libGraf.so
#11 0x00007f6174194271 in TLatex::Anal1(TLatex::TextSpec_t, char const*, int) () from /cvmfs/sft.cern.ch/lcg/releases/ROOT/6.14.04-0d8dc/x86_64-slc6-gcc62-opt/lib/libGraf.so
#12 0x00007f617418b5bf in TLatex::Analyse(double, double, TLatex::TextSpec_t, char const*, int) () from /cvmfs/sft.cern.ch/lcg/releases/ROOT/6.14.04-0d8dc/x86_64-slc6-gcc62-opt/lib/libGraf.so
#13 0x00007f6174194271 in TLatex::Anal1(TLatex::TextSpec_t, char const*, int) () from /cvmfs/sft.cern.ch/lcg/releases/ROOT/6.14.04-0d8dc/x86_64-slc6-gcc62-opt/lib/libGraf.so
#14 0x00007f617418b625 in TLatex::Analyse(double, double, TLatex::TextSpec_t, char const*, int) () from /cvmfs/sft.cern.ch/lcg/releases/ROOT/6.14.04-0d8dc/x86_64-slc6-gcc62-opt/lib/libGraf.so
#15 0x00007f6174194271 in TLatex::Anal1(TLatex::TextSpec_t, char const*, int) () from /cvmfs/sft.cern.ch/lcg/releases/ROOT/6.14.04-0d8dc/x86_64-slc6-gcc62-opt/lib/libGraf.so
#16 0x00007f61741943ff in TLatex::FirstParse(double, double, char const*) () from /cvmfs/sft.cern.ch/lcg/releases/ROOT/6.14.04-0d8dc/x86_64-slc6-gcc62-opt/lib/libGraf.so
#17 0x00007f6174196895 in TLatex::GetYsize() () from /cvmfs/sft.cern.ch/lcg/releases/ROOT/6.14.04-0d8dc/x86_64-slc6-gcc62-opt/lib/libGraf.so
#18 0x00007f6170e736e1 in THistPainter::PaintTitle() () from /cvmfs/sft.cern.ch/lcg/releases/ROOT/6.14.04-0d8dc/x86_64-slc6-gcc62-opt/lib/libHistPainter.so
#19 0x00007f6170e60b0a in THistPainter::Paint(char const*) () from /cvmfs/sft.cern.ch/lcg/releases/ROOT/6.14.04-0d8dc/x86_64-slc6-gcc62-opt/lib/libHistPainter.so
#20 0x00007f61744dba6c in TPad::Paint(char const*) () from /cvmfs/sft.cern.ch/lcg/releases/ROOT/6.14.04-0d8dc/x86_64-slc6-gcc62-opt/lib/libGpad.so
#21 0x00007f61744dba6c in TPad::Paint(char const*) () from /cvmfs/sft.cern.ch/lcg/releases/ROOT/6.14.04-0d8dc/x86_64-slc6-gcc62-opt/lib/libGpad.so
#22 0x00007f61744d850f in TPad::Print(char const*, char const*) () from /cvmfs/sft.cern.ch/lcg/releases/ROOT/6.14.04-0d8dc/x86_64-slc6-gcc62-opt/lib/libGpad.so
#23 0x00007f61744d91ce in TPad::SaveAs(char const*, char const*) const () from /cvmfs/sft.cern.ch/lcg/releases/ROOT/6.14.04-0d8dc/x86_64-slc6-gcc62-opt/lib/libGpad.so
#24 0x00007f618187a191 in ?? ()
#25 0x0000000000000000 in ?? ()
===========================================================


The lines below might hint at the cause of the crash.
You may get help by asking at the ROOT forum http://root.cern.ch/forum
Only if you are really convinced it is a bug in ROOT then please submit a
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.
===========================================================
#5  0x00007f6173e59ade in FT_Done_Glyph () from /cvmfs/sft.cern.ch/lcg/releases/LCG_94/freetype/2.6.3/x86_64-slc6-gcc62-opt/lib/libfreetype.so.6
#6  0x00007f61741c7191 in TTF::LayoutGlyphs() () from /cvmfs/sft.cern.ch/lcg/releases/ROOT/6.14.04-0d8dc/x86_64-slc6-gcc62-opt/lib/libGraf.so
#7  0x00007f61741c784f in TTF::GetTextExtent(unsigned int&, unsigned int&, char*) () from /cvmfs/sft.cern.ch/lcg/releases/ROOT/6.14.04-0d8dc/x86_64-slc6-gcc62-opt/lib/libGraf.so
#8  0x00007f61741916c4 in TLatex::Analyse(double, double, TLatex::TextSpec_t, char const*, int) () from /cvmfs/sft.cern.ch/lcg/releases/ROOT/6.14.04-0d8dc/x86_64-slc6-gcc62-opt/lib/libGraf.so
#9  0x00007f6174194271 in TLatex::Anal1(TLatex::TextSpec_t, char const*, int) () from /cvmfs/sft.cern.ch/lcg/releases/ROOT/6.14.04-0d8dc/x86_64-slc6-gcc62-opt/lib/libGraf.so
#10 0x00007f617418d1b7 in TLatex::Analyse(double, double, TLatex::TextSpec_t, char const*, int) () from /cvmfs/sft.cern.ch/lcg/releases/ROOT/6.14.04-0d8dc/x86_64-slc6-gcc62-opt/lib/libGraf.so
#11 0x00007f6174194271 in TLatex::Anal1(TLatex::TextSpec_t, char const*, int) () from /cvmfs/sft.cern.ch/lcg/releases/ROOT/6.14.04-0d8dc/x86_64-slc6-gcc62-opt/lib/libGraf.so
#12 0x00007f617418b5bf in TLatex::Analyse(double, double, TLatex::TextSpec_t, char const*, int) () from /cvmfs/sft.cern.ch/lcg/releases/ROOT/6.14.04-0d8dc/x86_64-slc6-gcc62-opt/lib/libGraf.so
#13 0x00007f6174194271 in TLatex::Anal1(TLatex::TextSpec_t, char const*, int) () from /cvmfs/sft.cern.ch/lcg/releases/ROOT/6.14.04-0d8dc/x86_64-slc6-gcc62-opt/lib/libGraf.so
#14 0x00007f617418b625 in TLatex::Analyse(double, double, TLatex::TextSpec_t, char const*, int) () from /cvmfs/sft.cern.ch/lcg/releases/ROOT/6.14.04-0d8dc/x86_64-slc6-gcc62-opt/lib/libGraf.so
#15 0x00007f6174194271 in TLatex::Anal1(TLatex::TextSpec_t, char const*, int) () from /cvmfs/sft.cern.ch/lcg/releases/ROOT/6.14.04-0d8dc/x86_64-slc6-gcc62-opt/lib/libGraf.so
#16 0x00007f61741943ff in TLatex::FirstParse(double, double, char const*) () from /cvmfs/sft.cern.ch/lcg/releases/ROOT/6.14.04-0d8dc/x86_64-slc6-gcc62-opt/lib/libGraf.so
#17 0x00007f6174196895 in TLatex::GetYsize() () from /cvmfs/sft.cern.ch/lcg/releases/ROOT/6.14.04-0d8dc/x86_64-slc6-gcc62-opt/lib/libGraf.so
#18 0x00007f6170e736e1 in THistPainter::PaintTitle() () from /cvmfs/sft.cern.ch/lcg/releases/ROOT/6.14.04-0d8dc/x86_64-slc6-gcc62-opt/lib/libHistPainter.so
#19 0x00007f6170e60b0a in THistPainter::Paint(char const*) () from /cvmfs/sft.cern.ch/lcg/releases/ROOT/6.14.04-0d8dc/x86_64-slc6-gcc62-opt/lib/libHistPainter.so
#20 0x00007f61744dba6c in TPad::Paint(char const*) () from /cvmfs/sft.cern.ch/lcg/releases/ROOT/6.14.04-0d8dc/x86_64-slc6-gcc62-opt/lib/libGpad.so
#21 0x00007f61744dba6c in TPad::Paint(char const*) () from /cvmfs/sft.cern.ch/lcg/releases/ROOT/6.14.04-0d8dc/x86_64-slc6-gcc62-opt/lib/libGpad.so
#22 0x00007f61744d850f in TPad::Print(char const*, char const*) () from /cvmfs/sft.cern.ch/lcg/releases/ROOT/6.14.04-0d8dc/x86_64-slc6-gcc62-opt/lib/libGpad.so
#23 0x00007f61744d91ce in TPad::SaveAs(char const*, char const*) const () from /cvmfs/sft.cern.ch/lcg/releases/ROOT/6.14.04-0d8dc/x86_64-slc6-gcc62-opt/lib/libGpad.so
#24 0x00007f618187a191 in ?? ()
#25 0x0000000000000000 in ?? ()
===========================================================

Thanks,
Dylan

couet · January 16, 2019, 3:06pm

I do not see any #pi in you code. I will try to make a reproducer.

couet · January 16, 2019, 3:09pm

it works for me:

root [0] auto h1 = new TH1D("h1","#pi",100,0,1); 
root [1] h1->Draw()
Info in <TCanvas::MakeDefCanvas>:  created default TCanvas with name c1
root [2] c1->SaveAs("h1.png");
Info in <TCanvas::Print>: file h1.png has been created
root [3]

DylanJW · January 16, 2019, 3:21pm

I am also able to get this simple example in the terminal to work. But when my script calls the function I showed above, that’s when it crashes.

There is no “#pi” hard-coded in to this function, it’s something to pass as an argument for ‘figureTitle’. However I tried editing the line “hist_a->SetTitle(figureTitle);” to “hist_a->SetTitle(”#pi");" and that still causes it to crash when it reaches the SaveAs line.

Upon further testing I seem to also be getting these errors when I try to draw the canvas:

 Fontconfig error: Cannot load default config file
Warning in <TPad::ResizePad>: Inf/NaN propagated to the pad. Check drawn objects.
Warning in <TPad::ResizePad>: padh height changed from 0 to 10

couet · January 16, 2019, 3:58pm

Cab you provide a small macro reproducing the problem ?

DylanJW · January 16, 2019, 4:20pm

I seem to have resolved the problem for all practical purposes. I was selecting only the first few thousand events from my NTuple, which was ordered, so the first plot had 0 entries. (This still doesn’t explain why it was happy to draw an empty figure only when I removed the latex script from the title however). Thank you for your help nonetheless!

system · January 30, 2019, 4:20pm

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