Trouble linking with extern

**amoskoh** · 03-21-2005

I have these files

Code:

//simgroup.h
#include <vector>
#include "simCmd.h"
vector<simCmd*> *cmdList1;

//driver.C
#include <vector>
extern vector<simCmd*> *cmdList1;


//Make command
INCLUDE = -I/usr/include
LIBRARYPATH = -L/usr/lib -L/usr/X11R6/lib/
LIBRARIES = $(LIBRARYPATH) -lGL -lGLU -lglut -lm -lXi -lXmu -lpthread

CC = g++
CFLAGS = -O2 $(INCLUDE)

SRCS = simGroup.C simCmd.C driver.C
OBJS = $(SRCS:.C=.o)
EXE = simStart

all: $(EXE)

clean:
        rm -rf core *~ *.o $(EXE)

$(EXE): $(OBJS) $(JLLIBS)
        $(CC) $(CFLAGS) -o $@ $(OBJS) $(LIBRARIES) $(FORMS_LIBS)

.C.o:
        $(CC) $(CFLAGS) $< -c -o $@

//error when calling make
g++ -O2 -I/usr/include driver.C -c -o driver.o
driver.C:12: syntax error before `*' token
make: *** [driver.o] Error 1

Line 12 is the "extern vector<simCmd*> *cmdList1;"

If I add this to driver.C #include "simgroup.C", it compiles driver.o but problem happens when linking . Error is..

Code:

g++ -O2 -I/usr/include driver.C -c -o driver.o
g++ -O2 -I/usr/include -o simStart simGroup.o simCmd.o driver.o -L/usr/lib -L/usr/X11R6/lib/ -lGL -lGLU -lglut -lm -lXi -lXmu -lpthread
driver.o(.text+0x52): In function `main':
: undefined reference to `cmdList1'
collect2: ld returned 1 exit status
make: *** [simStart] Error 1

I'm not too familiar with makefiles and this seems like a valid attempt of using extern to make cmdList1 a global variable.

**hk_mp5kpdw** · 03-21-2005

Maybe...

Code:

//simgroup.h
#include <vector>
#include "simCmd.h"
std::vector<simCmd*> *cmdList1;

//driver.C
#include <vector>
extern std::vector<simCmd*> *cmdList1;

**amoskoh** · 03-21-2005

I modified it to add 'using namespace std'

Code:

//simgroup.h
#include <vector>
#include "simCmd.h"
using namespace std;
vector<simCmd*> *cmdList1;

int main(){
  cmdList1[0] = bla bla //use of cmdList1 here
}

//driver.C
#include <vector>
using namespace std;
extern vector<simCmd*> *cmdList1;

I still get the error
driver.o(.text+0x52): In function `main':
: undefined reference to `cmdList1'
collect2: ld returned 1 exit status
make: *** [simStart] Error 1

somehow it wont recognize the cmdList1 inside main

If i add std::cmdList1 to all the parts whre cmdList1 appears I get the error

Code:

g++ -O2 -I/usr/include driver.C -c -o driver.o
driver.C: In function `int main(int, char**)':
driver.C:45: `cmdList1' undeclared in namespace `std'

**hk_mp5kpdw** · 03-21-2005

I just noticed something, you are compiling C source files and not C++ source files. You may need to change the extension of all your source files to whatever it needs to be (.CPP or .CC or whatever) so that the compiler understands to compile those files using C++ rules. Don't know for sure if that is part of the issue, I've never used g++.

[edit]Also, if cmdList1 is something you've developed on your own, then it won't be in the std namespace.[/edit]

**amoskoh** · 03-21-2005

simCmd is a class I created. Anyone with a fix yet? =(

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