Re: Fwd: TFile::Open(): distinguish application level and filesystem level errors

No, the code quoted below does not work -- the errno it references does not change:

root [2] errno=0
Warning: Automatic variable errno is allocated (tmpfile):1: (const int)0
root [3] f1=new TFile("g4beamline.root") // file exists (class TFile*)0x254ede0
root [4] errno
(int)0
root [5] f1->Close()
root [6] f1=new TFile("does not exist")
Error in <TFile::TFile>: file does not exist does not exist (class TFile*)0x254f490
root [7] f1->IsZombie()
(const Bool_t)(1)
root [8] errno
(int)0

The clue is the warning "Automatic variable errno is allocated", indicating this variable errno is UNRELATED to the errno used by the stdio library.

Doing "#include <stdio.h>" beforehand does not help. Doing "extern int errno" beforehand does not help. Using std::errno does not warn about allocating an automatic variable, but also does not change from 0 when calling TFile("does not exist").

I suppose it is possible that the code quoted below works when compiled with "#include <stdio.h>", but relying on that in a Cint environment seems risky to me....

Comment: the error message following root[6] above should put the filename in quotes (filenames can contain spaces).

Comment: Are there really two different "roottalk" mailing lists? If not, why the different email addresses?

Tom Roberts

On 2/17/11 2/17/11 - 3:50 AM, Fons Rademakers wrote:
> Hi Thiemo,
>
> yes that's fine.
>
> Cheers, Fons.
>
>
> On 17/02/11 10:17, Thiemo Nagel wrote:
>> Dear Konstantin, Fons,
>>
>> On 02/16/2011 09:09 PM, Konstantin Olchanski wrote:
>>> You can also cheat:
>>>
>>> errno = 0;
>>> TFile *f = new TFile( argv[1] );
>>> if (errno != 0)
>>> printf("system error %d (%s) somewhere inside TFile::Open", errno,
>>> strerror(errno));
>>
>> very interesting! If it is ok with the ROOT guys, I'd use this for the hadd
>> -k option.
>>
>> Cheers,
>> Thiemo
>
Received on Thu Feb 17 2011 - 17:17:28 CET