Spurious(?) warnings persisting interpreted classes #9371
Description
In some cases when trying to persist classes from ACLIC or the interpreter, there are warnings about missing dictionaries, which apparently don't prevent correctly persisting the class.
Real use case is persisting boost histogram templates instantiated with PyROOT, but a standalone example is included below.
#include "TFile.h"
#include <atomic>
#include <iostream>
class Test {
public:
std::atomic<double> &data() { return data_; }
const std::atomic<double> &data() const { return data_; }
private:
std::atomic<double> data_;
};
class Test2 : public std::atomic<double> {
};
int testio() {
Test t;
t.data() = 5.;
Test2 t2;
t2.store(5.);
TFile *fout = TFile::Open("test.root", "RECREATE");
fout->WriteObject(&t, "t");
fout->WriteObject(&t2, "t2");
fout->Close();
TFile *fin = TFile::Open("test.root");
auto &tread = *fin->Get<Test>("t");
auto &tread2 = *fin->Get<Test2>("t2");
std::cout << tread.data() << std::endl;
std::cout << tread2 << std::endl;
return 0;
}
The output is:
[bendavid@docker@lxplus8s10 boostiotest]$ root -l testio.cpp+
root [0]
Processing testio.cpp+...
Info in <TUnixSystem::ACLiC>: creating shared library /home/b/bendavid/boostiotest/./testio_cpp.so
Warning in <TStreamerInfo::Build>: Test: atomic<double> has no streamer or dictionary, data member "data_" will not be saved
Warning in <TStreamerInfo::Build>: Test2: base class atomic<double> has no streamer or dictionary it will not be saved
5
5
(int) 0
So apparently both classes (and the std::atomic data member and/or base class) are persisted just fine.