How to check existence of gDirectory

[mauroroot]

I used to use :

if (gDirectory != nullptr)

and it was working.
Now I get the following error:

/home/testbeam/eudaq-v1/monitors/onlinemon/src/EUDAQMonitorCollection.cc: In member function ‘virtual void EUDAQMonitorCollection::Write(TFile*)’:
/home/testbeam/eudaq-v1/monitors/onlinemon/src/EUDAQMonitorCollection.cc:36:18: error: ambiguous overload for ‘operator!=’ (operand types are ‘ROOT::Internal::TDirectoryAtomicAdapter’ and ‘std::nullptr_t’)
   if (gDirectory != nullptr) // check if this pointer exists
                  ^
/home/testbeam/eudaq-v1/monitors/onlinemon/src/EUDAQMonitorCollection.cc:36:18: note: candidates are:
/home/testbeam/eudaq-v1/monitors/onlinemon/src/EUDAQMonitorCollection.cc:36:18: note: operator!=(TDirectory*, TDirectory*) <built-in>
In file included from /home/testbeam/root/myBuild/include/TDirectoryFile.h:25:0,
                 from /home/testbeam/root/myBuild/include/TFile.h:28,
                 from /home/testbeam/eudaq-v1/monitors/onlinemon/src/../include/EUDAQMonitorCollection.hh:13,
                 from /home/testbeam/eudaq-v1/monitors/onlinemon/src/EUDAQMonitorCollection.cc:8:
/home/testbeam/root/myBuild/include/TDirectory.h:266:12: note: bool ROOT::Internal::TDirectoryAtomicAdapter::operator!=(const TDirectory*) const
       bool operator!=(const TDirectory *other) const {
            ^
/home/testbeam/root/myBuild/include/TDirectory.h:274:12: note: bool ROOT::Internal::TDirectoryAtomicAdapter::operator!=(TDirectory*) const
       bool operator!=(TDirectory *other) const {
            ^
/home/testbeam/eudaq-v1/monitors/onlinemon/src/HitmapCollection.cc: In member function ‘virtual void HitmapCollection::Write(TFile*)’:

Is there a way to check the existence of gDirectory?

_ROOT Version: 2.24.06
_Platform: CENTOS7
_Compiler: GCC 4.8.5

---

[Wile_E_Coyote]

Try: if (gDirectory)

[pcanal]

Did you try

if (!gDirectory)

[mauroroot]

Many thanks Wile and pcanal
It’s working indeed
The simplest solution indeed is the one that most likely fixes the problem

Cheers,

• Mauro.