Suggested improvement: TTree::GetEntry

ROOT
1

Hi,

I would like to suggest a small improvement in the documentation of TTree that could save some debugging time to users. Due to a bug in my program, I started to find only events with length 0. After a lot of cross-checks I discovered that all the branches were disabled ( SetBranchStatus( “name”, 0 ) ). Even if the behaviour of ROOT is perfectly consistent, I suggest to add in the documentation a caveat for a situation like this. In fact, in such a case TTree::GetEntry throws no error, but IMO this is still a symptom of something weird going on with branch statuses.

Regards,
Riccardo

2

Hi Riccardo,

The function GetEntry returns the number of bytes read. To detect your case and in any other error cases you ought to check the return value of GetEntry:[quote] // The function returns the number of bytes read from the input buffer.
// If entry does not exist the function returns 0.
// If an I/O error occurs, the function returns -1.[/quote.

Cheers,
Philippe.