explicit instaniation vs std::vector template how

[icegood]

#include <iostream>
#include <vector>
//using namespace std;

struct TCbDoubleBridgeBase_Candidates
{
public:
  int I;
  int J;
  //
  TCbDoubleBridgeBase_Candidates(int AI, int AJ)
  {
    I=AI;
    J=AJ;
  };
  inline bool operator < (const TCbDoubleBridgeBase_Candidates &other) const
  {
    int i=I-other.I;
    //
    if (i<0)
      return true;
    else if (i==0)
      return J<other.J;
    else 
      return false;
  }
};

template <typename T>
class CMain
{
public:
  CMain()
  {
    data.reserve(100);
  }
  std::vector<T> data;
};


int main()
{
  CMain<TCbDoubleBridgeBase_Candidates> cs;
  //
  
}

How to compile this code with option of gcc -fno-implicit-templates?

[icegood]

As i googled everything is worse than i expected:
http://gcc.gnu.org/ml/libstdc++/2006-09/msg00244.html
http://bytes.com/topic/c/answers/572842-explicit-instantiation-templates-any-experience

So, has someone worked code for all that stuff to share with?

[Catfish2]

Add this somewhere.
template class std::vector<TCbDoubleBridgeBase_Candidates>;

http://www.network-theory.co.uk/docs/gccintro/gccintro_60.html

God help you.

[icegood]

Nope...
Compiling is realy OK (http://ideone.com/NSFHtw),
but not linking. As i said, it's rather difficult issue

[guestgulkan]

To get that code to link a with the -fno-implicit-templates there are
two explicit instantiation that you need to do (although, I think one of then is not necessary. see below...)
The following compiles, links and runs..

#include <iostream>
#include <vector>
//using namespace std;

struct TCbDoubleBridgeBase_Candidates
{
public:
  int I;
  int J;
  //
  TCbDoubleBridgeBase_Candidates(int AI, int AJ)
  {
    I=AI;
    J=AJ;
  };
  inline bool operator < (const TCbDoubleBridgeBase_Candidates &other) const
  {
    int i=I-other.I;
    //
    if (i<0)
      return true;
    else if (i==0)
      return J<other.J;
    else 
      return false;
  }
};




template <typename T>
class CMain
{
public:
  CMain()
  {
    data.reserve(100);
  }
  std::vector<T> data;
};

//explicit instantiations
template class CMain<TCbDoubleBridgeBase_Candidates>; //the straightforward one - I'm not sure you need this one to be explicit
template class std::vector<TCbDoubleBridgeBase_Candidates>; //you will need this one though..


int main()
{
  
   CMain<TCbDoubleBridgeBase_Candidates> cs;
  
  
}

//You could put the explicit instantiations  here instead of before main if you prefer

[icegood]

Does it work on your computer?
In my one refuses int both cases (4.5.3 under cygwin and 4.7.2 under kubuntu)

output for cygwin:

$ gcc -fno-implicit-templates ex.cpp
/tmp/ccm9LSKx.o:ex.cpp:(.text+0x4a): undefined reference to `std::ios_base::Init::Init()'
/tmp/ccm9LSKx.o:ex.cpp:(.text+0x65): undefined reference to `std::ios_base::Init::~Init()'
/usr/lib/gcc/i686-pc-cygwin/4.5.3/../../../../i686-pc-cygwin/bin/ld: /tmp/ccm9LSKx.o: bad reloc address 0xd in section `.text$_ZN5CMainI30TCbDoubleBridgeBase_CandidatesED1Ev[CMain<TCbDoubleBridgeBase_Candidates>::~CMain()]'
/usr/lib/gcc/i686-pc-cygwin/4.5.3/../../../../i686-pc-cygwin/bin/ld: final link failed: Invalid operation
...

[Catfish2]

Please run g++ instead of gcc.

[icegood]

i do run g++ otherwise even stdc++ wouldn't linked at all

[JLBorges]

#include <iostream>
#include <vector>

struct TCbDoubleBridgeBase_Candidates { /* ... */ } ;

template < typename T > struct CMain
{
  CMain() { data.reserve(100) ; }
  private: std::vector<T> data;
};

// uncomment these if required (link errors)
// template struct std::allocator<TCbDoubleBridgeBase_Candidates> ;
// template struct std::char_traits<char> ;
// template struct std::basic_ios<char> ;

template struct std::vector< TCbDoubleBridgeBase_Candidates > ;
template struct CMain<TCbDoubleBridgeBase_Candidates> ;

template struct std::basic_ostream<char> ;
template struct std::basic_istream<char> ;

int main()
{
  CMain<TCbDoubleBridgeBase_Candidates> cs;

  // use standard stream objects (char)
}

[guestgulkan]

To be honest - the way I would figure out a situation like this would be to:

make sure the thing build completely without the -fno-implicit-templates option.

Then build with the -fno-implicit-templates option.

Any items that suddenly go MIA are the one that you need to
explicitly instantiate.


EDIT
((For the record I tried both G++ 3.4.5 and G++ 4.6.2 using codeblocks on windows
and although they gave sliglty different results, the issue of std::ios didn't come
up - it might well depends on what other baggage your ide/build system automatically includes ))

[icegood]

i probably did smth wrong. Everything works for me now.