[SOLVED] Unsuccessful debug using Makefile during integration of cpp code to c code

eryn · 05-12-2010, 09:50 PM

Hello everyone,

We have codes written in C language and C++ language.

We have successfully wrote wrapper code and debug using manual command and the code runs good.
Now, we need to eliminate this manual debug step by inserting them into Makefile.

Before that, let me explain the flow.

Our main running code is called core.c. In core.c, we called a function named ARMWashCycle(). This function is written and saved as arm.c. In function ARMWashCycle(), we called functions from cpp code and we did a wrapper code for this.

Here is our arm.c

Code:

#include <stdio.h>
#include <unistd.h>
#include "wrapper.h"
#include "arm.h"

int ARMWashCycle ( )
{
        int arm=0;

        libInit();
        libClose();

        return 0;
}

In core.c, we did include the arm.h header. This code is debugging fine when we do manual debug using the following command.

Step 1:

Code:

g++ -I<include path needed to compile cpp code> -c -DNUM_DRIVES=6 wrapper.cpp

Step 2:

Code:

gcc <CFLAGS> <PKG_CONFIG> -c core.c motor.c <all sub-code needed....>

Step 3:

Code:

g++ -o core <all object files needed> -lusb <Linker Flags> /home/user/rwc/Source/cmdapi/lib/libRWCCommanderApi.so.1.0.0 /home/user/rwc/Source/lib/lib/libBRBTeam.so.1.0.0

These will debug our code successfully and we can run the code.

Now, when we try to do the Makefile for this,

Makefile:

Code:

#------------------------------------------------------------------------------
# Linker Flags
#------------------------------------------------------------------------------
LDFLAGS := -L../lib
ifeq ($(OS),Linux)
        LDFLAGS += -L/usr/local/lib -lusb-1.0 -lm -lm /home/user/Source/cmdapi/lib/libRWCCommanderApi.so.1.0.0 -lm /home/user/Source/lib/lib/libBRBTeam.so.1.0.0

else
        LDFLAGS += -L../libusb/libusb-win32-src -lusb
endif

#------------------------------------------------------------------------------
# Common rules
#------------------------------------------------------------------------------
%.o:    %.c
        $(CC) -c $(CFLAGS) -o $@ $<


#------------------------------------------------------------------------------
# Target Builds
#
#------------------------------------------------------------------------------
wrapper.o : wrapper.cpp
        g++ -I/usr/share/qt4/mkspecs/linux-g++ -I. -I/usr/include/qt4/QtCore -I/usr/include/qt4/QtCore -I/usr/include/qt4/QtNetwork -I/usr/include/qt4/QtNetwork -I/usr/include/qt4/QtGui -I/usr/include/qt4/QtGui -I/usr/include/qt4 -I. -I../lib/include -I.moc -I. -c -DNUM_DRIVES=6 wrapper.cpp

arm.o : arm.c
        g++ -Wall -c arm.c

core : core.o motor.o switch.o analog.o echoclnt.o helper.o mapping.o wrapper.o arm.o
        $(CC) -o $@ $^ -lsub $(LDFLAGS)


clean:
        rm -f *.o *.out *.err *.exe *.a *.so core

Then, it will give us the following error:

Code:

core.c: In function ‘main’:
core.c:160: warning: implicit declaration of function ‘ARMWashCycle’

core.o: In function `main':
/home/user/rwc/core/core.c:160: undefined reference to `ARMWashCycle'
collect2: ld returned 1 exit status
make: *** [core] Error 1

Anyone knows how can we solve this?
We have tried include the library path in /etc/ld.so.conf and run "ldconfig". It returns the same result.

When we close the function call of ARMWashCycle() in core.c, the debug will be successful.

JohnGraham · 05-13-2010, 01:56 AM

Quote:

Originally Posted by eryn

Code:

core.c: In function ‘main’:
core.c:160: warning: implicit declaration of function ‘ARMWashCycle’

core.o: In function `main':
/home/user/rwc/core/core.c:160: undefined reference to `ARMWashCycle'
collect2: ld returned 1 exit status
make: *** [core] Error 1

First, /etc/ld.so.conf and ldconfig are to do with run-time linking - what you have here is a link-time problem, so fiddling with them won't help one bit.

Secondly, case matters in C - your code defines ArmWashCycle but then later references ARMWashCycle.

But what you REALLY want to do is to have used -Werror so the first error stops you in your tracks and you're forced to fix it, meaning you'll never get distracted by the second error.

eryn · 05-13-2010, 02:51 AM

About the case matter, we have checked in the program, it is 100% identical. Just typo error when tried to post a new thread.

The first is not really an error, it is just a warning. Code can still be debug successfully with warning, right?

JohnGraham · 05-13-2010, 12:12 PM

Quote:

Originally Posted by eryn

The first is not really an error, it is just a warning. Code can still be debug successfully with warning, right?

That's correct - but I wouldn't advise it. You'll thank yourself later. -Werror is your friend, as is -Wall.

Anyway, in that case your problem is that you use g++ to compile arm.o, but $(CC) to compile core, and the name mangling is what messes things up. Switch to using only a C compiler or a C++ compiler, or use extern "C" if you want to mix.

eryn · 05-13-2010, 09:36 PM

Thank you, John.
We solved the problem with extern "C"
Here is what we have modified.

In arm.h

Code:

#ifdef __cplusplus
extern "C"
{
#endif

#include<stdio.h>
#include<unistd.h>
#include "wrapper.h"

int ARMWashCycle ( );
#ifdef __cplusplus
}
#endif