Question

0

Makefile: how to change a specific rule

rated 0 times [ 0] [ 0] / answers: 1 / hits: 953 / 2 Years ago, wed, may 18, 2022, 8:31:37

this is my first question here, I hope to do everything in the right way.

I'm a quite new Ubuntu user and if possible I need some help with a specific Makefile. I downloaded QEMU 2.1.0 and I'm currently changing some source code files for a custom version. In particular I have an sd.c file like the following:

[...]

#include "hw/mydistribution.h"

[...]

Nac = poisson_distribution(Nac_mean);

and a mydistribution.h file where for example I define the poisson_distribution() using functions from GSL library:

#include <math.h>

#include <gsl/gsl_rng.h>

#include <gsl/gsl_randist.h>

[...]

unsigned int poisson_distribution(double expected_value) {



const gsl_rng_type * T;

gsl_rng * r;

unsigned int k;



gsl_rng_env_setup();

T = gsl_rng_default;

r = gsl_rng_alloc (T);

k = gsl_ran_poisson (r, expected_value);

gsl_rng_free (r);



return k;

}

Now, I know that if I had all the aforementioned parts in the same file [e.g. myfile.c] I could compile from terminal using:

gcc myfile.c -o myfile -lgsl -lgslcblas -lm

and it works because I tried. But how to ask to QEMU Makefile to do this? honestly this Makefile seems too complex for my entry level. I googled info about makefiles and after reading I thought to find in QEMU Makefile something like:

LDLIBS := -lgsl -lgslcblas -lm

[...]

$(CC) -o $@ $^ $(LDLIBS)

but searching for the real QEMU Makefile implementation I found the rules.mak file where:

%.o: %.c

    $(call quiet-command,$(CC) $(QEMU_INCLUDES) $(QEMU_CFLAGS) $(QEMU_DGFLAGS) $(CFLAGS) $($@-cflags) -c -o $@ $<,"  CC    $(TARGET_DIR)$@")

Maybe this is the line to tweak. The question is: how to tweak? I tried to edit this line as:

%.o: %.c

    $(call quiet-command,$(CC) $(QEMU_INCLUDES) $(QEMU_CFLAGS) $(QEMU_DGFLAGS) $(CFLAGS) $($@-cflags) -c -o $@ $< -lgsl -lgslcblas -lm,"  CC    $(TARGET_DIR)$@")

but it didn't work and I got the following errors

ubuntu@ubuntu:~/Desktop/qemu-2.1.0$ make

  GEN   config-host.h

  GEN   trace/generated-tracers.h

  GEN   trace/generated-tracers.c

  GEN   arm-softmmu/config-target.h

  LINK  arm-softmmu/qemu-system-arm

../hw/sd/sd.o: In function `poisson_distribution':

/home/ubuntu/Desktop/qemu-2.1.0/include/hw/mycard.h:1630: undefined reference to `gsl_rng_env_setup'

/home/ubuntu/Desktop/qemu-2.1.0/include/hw/mycard.h:1632: undefined reference to `gsl_rng_default'

/home/ubuntu/Desktop/qemu-2.1.0/include/hw/mycard.h:1633: undefined reference to `gsl_rng_alloc'

/home/ubuntu/Desktop/qemu-2.1.0/include/hw/mycard.h:1641: undefined reference to `gsl_ran_poisson'

/home/ubuntu/Desktop/qemu-2.1.0/include/hw/mycard.h:1646: undefined reference to `gsl_rng_free'

../hw/sd/sd.o: In function `weibull_distribution':

/home/ubuntu/Desktop/qemu-2.1.0/include/hw/mycard.h:1676: undefined reference to `gsl_rng_env_setup'

/home/ubuntu/Desktop/qemu-2.1.0/include/hw/mycard.h:1678: undefined reference to `gsl_rng_default'

/home/ubuntu/Desktop/qemu-2.1.0/include/hw/mycard.h:1679: undefined reference to `gsl_rng_alloc'

/home/ubuntu/Desktop/qemu-2.1.0/include/hw/mycard.h:1687: undefined reference to `gsl_ran_weibull'

/home/ubuntu/Desktop/qemu-2.1.0/include/hw/mycard.h:1692: undefined reference to `gsl_rng_free'

collect2: error: ld returned 1 exit status

make[1]: *** [qemu-system-arm] Error 1

make: *** [subdir-arm-softmmu] Error 2

And after all I think it would not be a perfect solution since the other files don't need GSL library and there's no need to apply -lgsl -lgslcblas -lm to every .c file. I would like to create a new Makefile where all the other files continue to be compiled like the original Makefile but when it comes to sd.c I would like it to be compiled as said before in order to avoid undefined references

Thanks in advance to the persons that will give me precise suggestions to help me fix this issue

Answers

Only authorized users can answer the question. Please sign in first, or register a free account.

arkcker

Add To Favorites

Follow

Total Points: 296

Total Questions: 111

Total Answers: 104

Location: Nepal

Member since Tue, Sep 8, 2020

4 Years ago

answered 2 Years ago kneducator · Accepted Answer

I think after days of doubts, researches, manuals and so on I finally solved my problem and I want to share my efforts with you

After steeldriver comment I began to watch more closely the linking phase. The solution I found was adding the following lines to configure file just before the analogue librt section:

##########################################

# Do we need libgsl0-dev

cat > $TMPC << EOF

#include <gsl/gsl_rng.h>

#include <gsl/gsl_randist.h>

int main(void) { return (int) gsl_ran_weibull_pdf (11, 10, 5); }

EOF

if compile_prog "" "" ; then

  :

elif compile_prog "" "-lgsl -lgslcblas" ; then

  LIBS="-lgsl -lgslcblas $LIBS"

  libs_qga="-lgsl -lgslcblas $libs_qga"

else

  error_exit "libgsl0-dev check failed"

fi

the purpose of gsl_ran_weibull_pdf (11, 10, 5) is verifying the presence of libgsl0-dev. If we have it than when we find -lgsl -lgslcblas we can correctly interpretate them, else the user will be informed about the absence of this library

Now when I type:
ubuntu@ubuntu:~/Desktop/qemu-2.1.0$ make

there are no more undefined references:

  GEN   config-host.h

  GEN   trace/generated-tracers.h

  GEN   trace/generated-tracers.c

  CC    hw/sd/sd.o

  GEN   arm-softmmu/config-target.h

  LINK  arm-softmmu/qemu-system-arm

  GEN   arm-linux-user/config-target.h

I'm sure this solution can be further refined and I'm open to new suggestions, if any. But I admit to be already extremely happy in finding this result

Special thanks to @muru and @steeldriver for their support