[Bug c++/44855] New: Static members not initialised in explicit template instances of library

[Bug c++/44855] New: Static members not initialised in explicit template instances of library

[hlprasu at gmail dot com]

Consider the following C++ source code files

=========> testLib.h <===========
#include <stdexcept>
#include <iostream>

#define DEBUG1(X) std::cout<<X;

typedef int IndexType;

namespace Upagraha
{

template<typename X,int Size>
class CompileTimeFixedSizeData
{

protected:
        X _data[Size];          //!< The storage of the data
        static IndexType _size; //!< The size of the data.
public:
        CompileTimeFixedSizeData()
        {
          DEBUG1("Template value = "<< Size << std::endl);
          DEBUG1("Static variable value = "<< _size<< std::endl);
        }

        virtual ~CompileTimeFixedSizeData()
        {}
};


//setting the value of _size, which is static
template<typename X,int Size>
IndexType CompileTimeFixedSizeData<X,Size>::_size=Size;

/** Create an instance of CompileTimeFixedSizeData and associated functions. 
 */
#define COMPILE_TIME_FIXED_SIZE_DATA_INSTANCE(TYPE,SIZE) \
        template class CompileTimeFixedSizeData<TYPE,SIZE>;

}

=========> testLib.cpp <===========
#include "testLib.h"
namespace Upagraha
{
        COMPILE_TIME_FIXED_SIZE_DATA_INSTANCE(double,3)
}

=========> main.cpp <===========
#include "testLib.h"

namespace Upagraha {
//extern template class CompileTimeFixedSizeData<double,3>;
// FIXME: Uncomment to see a change in behavior
}

int main()
{
        Upagraha::CompileTimeFixedSizeData<double,3> a;
}


=========> makefile <===========

#OPTIONS=-rdynamic -fno-implicit-templates -fPIC
OPTIONS=-rdynamic -fno-implicit-templates
# FIXME: Uncomment the top one to see change in behaviour

test:libtestLib.so testLib.h main.cpp
        g++ $(OPTIONS) $(TOPTIONS) main.cpp -L"${PWD}" -ltestLib -o main 

libtestLib.so: testLib.cpp testLib.h
        g++ $(OPTIONS) $(TOPTIONS) -shared testLib.cpp -o libtestLib.so

clean:
        rm main libtestLib.so *~

====================================

Put the above four files in same the directory and do the following
*) make
*) export LD_LIBRARY_PATH="$PWD"
*) ./main

You'll see the output as 
=====================
Template value = 3
Static variable value = 0
=====================

Now, follow either of the two "FIXME"s and build the program and run to get
=====================
Template value = 3
Static variable value = 3
=====================

Why this difference in behaviour in initialisation of static variable
Upagraha::CompileTimeFixedSizeData<X,Size>::_size? Could somebody please
explain this?


-- 
           Summary: Static members not initialised in explicit template
                    instances of library
           Product: gcc
           Version: 4.4.4
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: hlprasu at gmail dot com
 GCC build triplet: i686-redhat-linux
  GCC host triplet: i686-redhat-linux
GCC target triplet: i686-redhat-linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44855

[Bug c++/44855] Static members not initialised in explicit template instances of library

[hlprasu at gmail dot com]

------- Comment #1 from hlprasu at gmail dot com  2010-07-07 07:22 -------
Created an attachment (id=21120)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=21120&action=view)
The test case attached

To simplify the task of whomsoever who wants to see the behaviour, all the
files mentioned in my previous post is packaged in a tar.bz2 file attached
here.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44855

[Bug c++/44855] Static members not initialised in explicit template instances of library

[redi at gcc dot gnu dot org]

------- Comment #2 from redi at gcc dot gnu dot org  2010-07-07 09:18 -------
You need to use -fPIC for a shared object, so the version without that is not
valid.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44855

[Bug c++/44855] Static members not initialised in explicit template instances of library

[hlprasu at gmail dot com]

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------- Comment #3 from hlprasu at gmail dot com  2010-07-07 09:30 -------
Subject: Re:  Static members not initialised in explicit 
        template instances of library

But, as I know, no where is it mentioned to be necessary for static
member initialisation. Why should the compiler allow for such a subtle
error? Or is this documented somewhere?

Besides this issue, I've not faced any other problem in using shared
library by not using -fPIC. Could you please point out the necessary
implications that I am missing here?


On 7 July 2010 14:48, redi at gcc dot gnu dot org
<gcc-bugzilla@gcc.gnu.org> wrote:
>
>
> ------- Comment #2 from redi at gcc dot gnu dot org  2010-07-07 09:18 -------
> You need to use -fPIC for a shared object, so the version without that is not
> valid.
>
>


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44855

[Bug c++/44855] Static members not initialised in explicit template instances of library

[pinskia at gcc dot gnu dot org]

------- Comment #4 from pinskia at gcc dot gnu dot org  2010-07-25 02:04 -------
Well for x86_64 we get an error:
/usr/bin/ld: testLib.o: relocation R_X86_64_32 against `a local symbol' can not
be used when making a shared object; recompile with -fPIC


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44855

[Bug c++/44855] Static members not initialised in explicit template instances of library

[pinskia at gcc dot gnu dot org]

------- Comment #5 from pinskia at gcc dot gnu dot org  2010-07-25 02:13 -------
Works for me on the trunk and in 4.3.2.

Can you give the output of "gcc -v"?


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |WAITING


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44855

[Bug c++/44855] Static members not initialised in explicit template instances of library

[hlprasu at gmail dot com]

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------- Comment #6 from hlprasu at gmail dot com  2010-07-25 06:35 -------
Subject: Re:  Static members not initialised in explicit 
        template instances of library

Output of "gcc -v" is given below. I'm using Fedora 13 (with updates
till July 24, 2010). The error still persists.
===================
Using built-in specs.
Target: i686-redhat-linux
Configured with: ../configure --prefix=/usr --mandir=/usr/share/man
--infodir=/usr/share/info
--with-bugurl=http://bugzilla.redhat.com/bugzilla --enable-bootstrap
--enable-shared --enable-threads=posix --enable-checking=release
--with-system-zlib --enable-__cxa_atexit
--disable-libunwind-exceptions --enable-gnu-unique-object
--enable-languages=c,c++,objc,obj-c++,java,fortran,ada
--enable-java-awt=gtk --disable-dssi
--with-java-home=/usr/lib/jvm/java-1.5.0-gcj-1.5.0.0/jre
--enable-libgcj-multifile --enable-java-maintainer-mode
--with-ecj-jar=/usr/share/java/eclipse-ecj.jar
--disable-libjava-multilib --with-ppl --with-cloog --with-tune=generic
--with-arch=i686 --build=i686-redhat-linux
Thread model: posix
gcc version 4.4.4 20100630 (Red Hat 4.4.4-10) (GCC)
===================

On 25 July 2010 07:43, pinskia at gcc dot gnu dot org
<gcc-bugzilla@gcc.gnu.org> wrote:
> ------- Comment #5 from pinskia at gcc dot gnu dot org  2010-07-25 02:13 -------
> Works for me on the trunk and in 4.3.2.
>
> Can you give the output of "gcc -v"?
>


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44855

[Bug c++/44855] Static members not initialised in explicit template instances of library

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44855

Paolo Carlini <paolo.carlini at oracle dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|WAITING                     |RESOLVED
                 CC|gcc-bugs at gcc dot gnu.org |
         Resolution|                            |INVALID

--- Comment #9 from Paolo Carlini <paolo.carlini at oracle dot com> 2011-10-02 10:19:01 UTC ---
Closing.

[Bug c++/44855] Static members not initialised in explicit template instances of library

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44855

--- Comment #8 from Jonathan Wakely <redi at gcc dot gnu.org> 2011-03-29 19:51:15 UTC ---
I should have read the code properly ... if you've suppressed implicit
instantiation in main.cpp and you want the explicit instantiation in a shared
object to be used I would expect that you need to *either* use -fpic so the
instantiation in the .so is used *or* declare the explicit instantiation by
uncommenting the "extern template" declaration.

So I think the behaviour you're seeing is normal

[Bug c++/44855] Static members not initialised in explicit template instances of library

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44855

--- Comment #7 from Jonathan Wakely <redi at gcc dot gnu.org> 2011-03-29 19:05:32 UTC ---
I can reproduce this on Fedora 13

using -fpic or -fPIC fixes it (as well as avoiding SELinux "permission denied"
errors when loading the shared object)