Strange behavior of global in a namespace

[MichaelR]

Hi all!

I want to access a global variable in a namespace I put in a shared library. What I observe is that this fails unless I also declare a variable outside any namespace. Consider these files:

test.h

#pragma once

extern double outside;

namespace test {
extern double inside;
}

test.cpp

#include “test.hpp”

double outside;
double test::inside;

test_LinkDef.hpp

#ifdef CINT
#pragma link off all globals;
#pragma link off all classes;
#pragma link off all functions;
#pragma link C++ nestedclasses;

#pragma link C++ global outside;

#pragma link C++ namespace test;
#pragma link C++ global test::inside;
#endif

build.sh

#!/bin/bash
. /opt/root/6.20.00/bin/thisroot.sh
rootcint -f test_dict.cpp test.hpp test_LinkDef.hpp

c++ -std=c++17 -fPIC -c test.cpp
c++ -std=c++17 -fPIC -I /opt/root/6.20.00/include -c test_dict.cpp
c++ -std=c++17 -fPIC -shared -o libTest.so test.o test_dict.o -rdynamic

I execute build.sh to compile libTest.so, and all is fine:

root [0] gSystem->Load(“libTest.so”);
root [1] outside
(double) 0.0000000
root [2] test::inside
(double) 0.0000000

Now I remove the
#pragma link C++ global outside;
line in test_LinkDef.hpp and try again:

root [0] gSystem->Load(“libTest.so”);
root [1] test::inside
ROOT_prompt_1:1:1: error: ‘test’ is not a class, namespace, or enumeration
test::inside
^
ROOT_prompt_1:1:1: note: ‘test’ declared here

If this is expected behaviror, it’s at least very strange…
For now, I just have a dummy variable and am fine with it. Still I’d like to know whether I’m doing something wrong, or if I found a bug.

Cheers,
Michael

ROOT Version: 6.20.00
Platform: Linux
Compiler: gcc version 9.2.1 20191008 (Ubuntu 9.2.1-9ubuntu2)

---

[MichaelR]

addendum:
The entry outside namespace need not only be preset, but I have to access it in the root session, before I can access any member in the namespace.
I.e.

root [0] gSystem->Load(“libTest.so”);
root [1] test::inside
ROOT_prompt_1:1:1: error: ‘test’ is not a class, namespace, or enumeration
test::inside
^
ROOT_prompt_1:1:1: note: ‘test’ declared here
root [2] outside
(double) 0.0000000
root [3] test::inside
(double) 0.0000000

[Axel]

That indeed looks like a bug; you’re welcome to submit this as a bug report. Either way I’ll have to debug it. Thanks for reporting and for the reproducer!

[MichaelR]

OK, I created a report: https://sft.its.cern.ch/jira/browse/ROOT-10604