RootUtils::PyROOTTypePatch Class Reference

Work around pyroot problem with __pair_base. More...

#include <PyROOTTypePatch.h>

Collaboration diagram for RootUtils::PyROOTTypePatch:

Static Public Member Functions
static void	initialize ()
	Initialize the workaround. More...
static void	scan_one (TClass *cls)
	Scan a single class. More...

Detailed Description

Work around pyroot problem with __pair_base.

In gcc8, std::pair derives from the (empty) base class std::__pair_base. When ROOT makes dictionaries, it likes to strip std:: qualifiers. When it then tries to look up cling information for a TClass, if the lookup fails, it tries again with the std:: reinserted for all STL classes (with TClassEdit::InsertStd()). However, that doesn't work for __pair_base, because it's not a class that ROOT knows about. The upshot is that we see errors like:

Error in <TClass::LoadClassInfo>: no interpreter information for class __pair_base<unsigned int,string> is available even though it has a TClass initialization routine.

We work around this by hooking into ROOT's TClass creation. If we see a std::pair class, we erase the base class information from its TClass.

Definition at line 42 of file PyROOTTypePatch.h.

Member Function Documentation

initialize()

void RootUtils::PyROOTTypePatch::initialize ( )

static

Initialize the workaround.

Scan all known classes, and also hook into class creation so that we'll scan all future classes.

Definition at line 134 of file PyROOTTypePatch.cxx.

{
  // Return if we've already initialized.
  static bool initialized = false;
  if (initialized) return;
  initialized = true;
 
  // Scan all classes.
  scan_for_pair();
 
  // Register ourselves as a hook,
  // to be called in the future on class creation.
  TypePatchInitBehavior::oldBehaviorPtr = &TypePatchInitBehavior::oldBehavior;
  TInitBehavior* ib =
    const_cast<TInitBehavior*>(DefineBehavior(0,0));
  assert (sizeof(TDefaultInitBehavior) == sizeof (TypePatchInitBehavior));
  memcpy ((char*)&TypePatchInitBehavior::oldBehavior, (char*)ib,
          sizeof(TDefaultInitBehavior));
  static TypePatchInitBehavior sfaib;
  memcpy ((char*)ib, (char*)&sfaib, sizeof(TDefaultInitBehavior));
 
  // Make sure the TClass's for these are built.
  // Otherwise, CreateClass can get called while global dtors are running.
  gROOT->GetClass("TObjString");
  gROOT->GetClass("TTreeCache");
}

scan_one()

void RootUtils::PyROOTTypePatch::scan_one ( TClass *  cls )

static

Scan a single class.

Parameters

cls	The class to scan.

Definition at line 166 of file PyROOTTypePatch.cxx.

{
  if (name_is_pair (cls->GetName())) {
    cls->GetListOfBases()->Clear();
  }
}

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The documentation for this class was generated from the following files:

• PyROOTTypePatch.h
• PyROOTTypePatch.cxx