[Bug c++/11652] New: incorrect template instantiation in some circumstances

[yangg2 at rpi dot edu]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11652

           Summary: incorrect template instantiation in some circumstances
           Product: gcc
           Version: 3.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: yangg2 at rpi dot edu
                CC: gcc-bugs at gcc dot gnu dot org

---------------- temp.cxx ---------------------------------
#include <vector>
#include <iostream>

// a template class definition
// but it cannot be instantiated without 
// the definition of function by_val()
template<class T>
class container {
  T a; 
  T* b;
public:
  T* by_addr() const { return b; }
  T  by_val()  const;
  int size() const { return 100; }
};

class trace_pt {
  int i;
};

// with template class definition
// we can define varibles in template type
// note that this variable definition would not
// trigger template instantiation because it still
// lacks of one member function
class trace {
  container<trace_pt> a_;
public:
  int size() const { return a_.size(); }
};

// supply member function definition here
template<class T>
T container<T>::by_val() const 
{
  return a;
}


// do explicit template instantiation
// At this point, it should be able to
// compile the template code
template class container<trace_pt>;
------------------------ END -------------------------------

Symtom: GCC3.3 would not generate (extern) symbol and code for 
container<trace_pt>::size() function. But some other previous versions of GCC 
do NOT have this problem (including GCC 2.95, 3.04, and 3.2).

Here are the nm results from object files of different GCC versions:
pre yangg2 $ g++295 -o temp.o -c temp.cxx 
pre yangg2 $ nm -Cg temp.o | grep size
00000000 W container<trace_pt>::size(void) const

pre yangg2 $ g++304  -o temp.o -c temp.cxx 
pre yangg2 $ nm -Cg | grep size                                  
00000000 W container<trace_pt>::size() const

pre yangg2 $ g++33 -o temp.o -c temp.cxx 
pre yangg2 $ nm -Cg temp.o | grep size
pre yangg2 $
pre yangg2 $ nm -C temp.o | grep by_addr
00000000 W container<trace_pt>::by_addr() const


As we can see, only GCC3.3 does not generate the code for function 
container<trace_pt>::size() and this function only. 



----------- My GCC configurations -----------------
pre yangg2 $ g++295 -v
Using builtin specs.
gcc version 2.95.4 20020320 [FreeBSD]

pre yangg2 $ g++33 -v
Reading specs from /usr/local/bin/../lib/gcc-lib/i386-unknown-
freebsd4.8/3.3/specs
Configured with: ../gcc-3.3/configure --prefix=/software/gcc-3.3-0/pkg --
localstatedir=/var --disable-nls --program-suffix=33 --enable-shared --enable-
version-specific-runtime-libs
Thread model: posix
gcc version 3.3

pre yangg2 $ gcc304 -v
Reading specs from /usr/local/bin/../lib/gcc-lib/i386-unknown-
freebsd4.5/3.0.4/specs
Configured with: ../gcc-3.0.4/configure --prefix=/servers/sys/packages/gcc-
3.0.4-1 --enable-version-specific-runtime-libs
Thread model: posix
gcc version 3.0.4

-------------------- end -------------------------------