Problem linking object with extern "C"

[Andrew Hardy]

I am compiling some 'C' source code and some 'C++' source code.  The C++
source code has 'C' functions with C++ features in the function body.  The
C++ header, where C___plusplus is defined has the function declarations in
an extern "C" block.

It is my understanding that this will enable the linker to assosiate
function calls in the 'C' compiled object file with the 'C' functions in
the 'C++' compiled object file.  However although the C code and the C++
code both compile successfully I cannot get them to link.  Although I felt
I had got the syntax etc correct, I have tried several changes in a vain
attempt to get this working, including compiling the C++ with CC and with
gcc, moving the extern "C" around the header include instaed of in the
header file around the function declarations and also placing the function
definitions in an extern "C" block, and others, all to no avail.

If I remove any C++ features from the function definitions linking
succeeds, but as soon as I introduce any C++ feature to the function body,
then compile succeeds, but linking fails.  I undewrstood the idea of this
feature was to allow C++ code to provide a 'C' interface for C code to call
and pass agruments!

Any help would be grately appreciated.

Here is the header:

      #ifdef __cplusplus
      #include <string>
      #include <ostream>

      extern "C"
      {
      #endif


      void loadLookupData(void);
      void getValueName(char *ob,  char *val, char *valName);
      void getValueNameForRole(char *ob, char *val, char *rt, char *rv,
      char *valName);

      #ifdef __cplusplus
      }
      #endif

Here is the source code ( I plan to have much more in the functions, but am
trying to get the lnking to work.

      #include "import_lookup.h"

      void loadLookupData(void)
      {
      }

      void getValueName(char *ob,  char *val, char *valName)
      {
          char x[100] = "hi there";
          std::string rtString("0");
      }

      void getValueNameForRole(char *ob, char *val, char *rt, char *rv,
      char *valName)
      {
      }

Here is a fragment of the compile all with gcc:

      gcc -g -O2 -Wall -Wmissing-prototypes -Wstrict-prototypes
      -fexceptions -DHAVE_EXPAT_CONFIG_H -I../expat/lib -I. -static -o
      find_role_characteristics look_up_support_functions.o
      find_role_characteristics.o -L../expat/lib -lexpat
      gcc -g -O2 -Wall -Wmissing-prototypes -Wstrict-prototypes
      -fexceptions -DHAVE_EXPAT_CONFIG_H -I../expat/lib -I. -o
      import_lookup.o -c import_lookup.cpp
      import_lookup.cpp: In function `void getValueName(char *, char *,
      char *)':
      import_lookup.cpp:12: warning: unused variable `char x[100]'
      gcc -g -O2 -Wall -Wmissing-prototypes -Wstrict-prototypes
      -fexceptions -DHAVE_EXPAT_CONFIG_H -I../expat/lib -I. -o
      import_functions.o -c import_functions.c
      gcc -g -O2 -Wall -Wmissing-prototypes -Wstrict-prototypes
      -fexceptions -DHAVE_EXPAT_CONFIG_H -I../expat/lib -I. -o
      import_ideas.o -c import_ideas.c
      import_ideas.c: In function `end':
      import_ideas.c:140: warning: unused variable `i'
      gcc -g -O2 -Wall -Wmissing-prototypes -Wstrict-prototypes
      -fexceptions -DHAVE_EXPAT_CONFIG_H -I../expat/lib -I. -static -o
      import_ideas import_lookup.o import_functions.o import_ideas.o
      -L../expat/lib -lexpat -L/usr/lib/ -L../../../arch_lib
      -L/usr/informix/lib -L/usr/informix/lib/esql -L/usr/informix/lib/cli
      -lcurses  -lthsql -lthasf -lthgen -lthos -lifgls -lifglx  -lsocket
      -lnsl -lgen
      Undefined                       first referenced
       symbol                             in file
      ostream::operator<<(char const *)   import_lookup.o
      endl(ostream &)                     import_lookup.o
      __out_of_range(char const *)        import_lookup.o
      __length_error(char const *)        import_lookup.o
      cerr                                import_lookup.o
      ld: fatal: Symbol referencing errors. No output written to
      import_ideas
      collect2: ld returned 1 exit status
      *** Error code 1
      make: Fatal error: Command failed for target `import_ideas'

If I compile import_lookup.cpp with CC I get this:

      CC  -mt -O -I../../../../arch/source/library/include -DARCH_EPILOGUE
      -c -o import_lookup.o import_lookup.cpp
      gcc -g -O2 -Wall -Wmissing-prototypes -Wstrict-prototypes
      -fexceptions -DHAVE_EXPAT_CONFIG_H -I../expat/lib -I. -o
      import_functions.o -c import_functions.c
      gcc -g -O2 -Wall -Wmissing-prototypes -Wstrict-prototypes
      -fexceptions -DHAVE_EXPAT_CONFIG_H -I../expat/lib -I. -o
      import_ideas.o -c import_ideas.c
      import_ideas.c: In function `end':
      import_ideas.c:140: warning: unused variable `i'
      gcc -g -O2 -Wall -Wmissing-prototypes -Wstrict-prototypes
      -fexceptions -DHAVE_EXPAT_CONFIG_H -I../expat/lib -I. -static -o
      import_ideas import_lookup.o import_functions.o import_ideas.o
      -L../expat/lib -lexpat -L/usr/lib/ -L../../../arch_lib
      -L/usr/informix/lib -L/usr/informix/lib/esql -L/usr/informix/lib/cli
      -lcurses  -lthsql -lthasf -lthgen -lthos -lifgls -lifglx  -lsocket
      -lnsl -lgen
      Undefined                       first referenced
       symbol                             in file
      __1cDstdMbasic_string4Ccn0ALchar_traits4Cc__n0AJallocator4Cc___J__nullref_
 import_lookup.o
      __1c2k6Fpv_v_                       import_lookup.o
      __1cDstdMbasic_string4Ccn0ALchar_traits4Cc__n0AJallocator4Cc___2t6Mpkcrkn0C__v_
 import_lookup.o
      ld: fatal: Symbol referencing errors. No output written to
      import_ideas
      collect2: ld returned 1 exit status
      *** Error code 1
      make: Fatal error: Command failed for target `import_ideas'

Andrew H