Does TApplication change argv?

ROOT
1

Hi,

I have a quite strange problem with this little program:

int main(int argc, char **argv)
{
TApplication theApp(“App”, &argc, argv);

std::cout << argc << std::endl;
for (unsigned int nfiles = 1 ; nfiles < argc ; nfiles++)
{
std::cout << nfiles << “\t” << argv[nfiles] << std::endl;
}
theApp.Run();
return 0;
}

If I leave the TApplication theApp(…) at the top then this call of TrackingAna.exe ignores the input argument:

./TrackingAna.exe
/home/wildauer/data/data10_7TeV.00165956.express_express.vtxmon.D3PD_TRK.x44_c331._0001.1

and the print out is just
1
(which is num arguments and the first on is the program itself).

If I move TApplication past the print out then everything is fine. It prints
2
/home/wildauer/data/data10_7TeV.00165956.express_express.vtxmon.D3PD_TRK.x44_c331._0001.1

now the fun part is if I change the argument i.e. replace the .1 at the end with .2 then it works again …
any other string but the one above seems to work.

When I give 2 arguments in the “non working” case and the first one is
/home/wildauer/data/data10_7TeV.00165956.express_express.vtxmon.D3PD_TRK.x44_c331._0001.1

and the second one is
blabla

then it prints:
2
blabla

meaning it ignores the first string again. I am very confused about what is going on here!

My root version is root_v5.26.00.Linux-slc5_amd64-gcc3.4

Cheers
Andi

2

Hi,

quick addendum. When I run the same on e.g. lxplus215 then this does not happen …

On my local machine it does. Both are SLC5 64bit, but on my local machine
I downloaded root and I am not using the afs version.

My version is:
v5.26.00.Linux-slc5_amd64-gcc3.4

on lxplus215 I use:
5.26.00/x86_64-slc5-gcc34-opt

which seems pretty similar to me …

I’ll change to use the afs version also on my machine, maybe it helps.

Cheers
Andi

3

Hi,

the problem is sort of solved. In the constructor of TApplication the content of argc and argv is indeed
"fiddled around" with which results (maybe a bug?) that it removes an argument like this:

/home/wildauer/data/data10_7TeV.00165956.express_express.vtxmon.D3PD_TRK.x44_c331._0001.1

The solution is to use the Argc() and Argv() methods of TApplication which give back the unchanged input argument list. A cout of argc and theApp.Argc() gives:
3
4
showing that in argv one argument is missing.

Cheers
Andi