library linking in a make file

[uma_iyer]

Hi All,

I am new to linux
I have created a library (mylib.a) in my own directory.
I want to link this library file to my test application. My test application resides in the same directory.
For this i am using make file which is giving some issues.
I would like to know how to do this.
Below is the snippet of my make file

#compiler
CC = gcc
#include files directory
INCLUDE = .
#options for development
CFLAGS = -g -Wall -ansi
mymain: main.o mylib.a
$(CC) -o -L mymain main.o -l mylib.a
main.o: main.c
$(CC) -I$(INCLUDE) $(CFLAGS) -c main.c

This make file is giving issues and not able to link and generate executable file.
help me in correcting make file

thanks

[tpl]

did you try something like this?

gcc -o mymain main.c -l./mylib.a

where that is an "el" as in "-lm"

[uma_iyer]

i tried the above option.
but it is not fine. still there are issues

[Lakshmipathi]

can you post the exact error messages ?

[Lakshmipathi]

Does this help ?

gcc -o mymain main.c -L /absolute/path/to/mylib_directory

or

gcc -o mymain main.c /absolute/path/to/mylib.a

[uma_iyer]

I am listing the make file of static library created
#compiler
CC = gcc
#Lib command
LIBCC = ar
#Lib flags
LIBFLAG = rv #rcs
#include files directory
INCLUDE = .
#options for development
CFLAGS = -g -Wall -ansi
libmylib.a: global.o
$(LIBCC) -$(LIBFLAG) libmylib.a
global.o: global.c global.h
$(CC) -I$(INCLUDE) $(CFLAGS) -c global.c

With the help of above make file i am able to generate libmylib.a
in the directory /root/user1/lib_ex
-------------------------------------------------------------------------------------
************************************************** ******************

I have sample test application (main.c in /root/user1/lib_ex) which will make use of functions defined in libmylib.a

At the command prompt, options tried are

Option 1: command at shell
gcc main.c -L /root/user1/lib_ex -lmylib -o main

Error
-------
/tmp/ccwKhJSz.o(.text+0x2f): In function `main':
: undefined reference to `add'
/tmp/ccwKhJSz.o(.text+0x59): In function `main':
: undefined reference to `sub'
/tmp/ccwKhJSz.o(.text+0x83): In function `main':
: undefined reference to `mul'
collect2: ld returned 1 exit status

Option 2:
I tried the above options and the error is same as above

Option 3:
With the make file for main

#compiler
CC = gcc
#include files directory
INCLUDE = .
#options for development
CFLAGS = -g -Wall -ansi
mymain: main.o
$(CC) -o mymain main.o -L/root/shobha/lib_ex -llibmylib
main.o: main.c
$(CC) -I$(INCLUDE) $(CFLAGS) -c main.c

Error
------------
gcc -o mymain main.o -L/root/shobha/lib_ex -llibmylib
/usr/bin/ld: cannot find -llibmylib
collect2: ld returned 1 exit status
make: *** [mymain] Error 1

Option 4:
With the little change in the above make file

#compiler
CC = gcc
#include files directory
INCLUDE = .
#options for development
CFLAGS = -g -Wall -ansi
mymain: main.o libmylib.a
$(CC) -o mymain main.o -L/root/shobha/lib_ex -llibmylib
main.o: main.c
$(CC) -I$(INCLUDE) $(CFLAGS) -c main.c

Error
------------
gcc -o mymain main.o -L/root/shobha/lib_ex -llibmylib
/usr/bin/ld: cannot find -llibmylib
collect2: ld returned 1 exit status
make: *** [mymain] Error 1

Option 5
The change in the make file includes,
mymain: main.o mylib.a
$(CC) -o mymain main.o -L/root/shobha/lib_ex -lmylib

Error is
--------------------
make: *** No rule to make target `mylib.a', needed by `mymain'. Stop.

[Lakshmipathi]

Hi uma_iyer,
hmm..from makefile i can't figure out the issue..it looks ok..Have you tested your source and library ,without using make file?
Doing so will help to check whether it's Makefile problem or problem with your custom library itself.

if you successfully created library then check its functions using nm command.

nm libmylib.a

Do you have all necessary functions from above output?

On main Makefile,what's

-llibmylib

[aram535]

I'm confused, are you trying to link it or build it statically?

If its linked the library, than your config has to tell the binary where to find it.

Add the custom lib to a dir where ld will look for it, or configure ld to look in your dir.

If you're not on a Linux system, LD_CONFIG the env variable controls where binary will look for the libraries it needs.

You can verify that the binary can find the library using ldd:

# ldd firefox-bin
linux-gate.so.1 => (0x0054a000)
libpthread.so.0 => /lib/libpthread.so.0 (0x006b9000)
libxul.so => not found
libmozjs.so => not found
libxpcom.so => not found
libplds4.so => /usr/lib/libplds4.so (0x0323f000)
libplc4.so => /usr/lib/libplc4.so (0x030bc000)
libnspr4.so => /usr/lib/libnspr4.so (0x030c2000)
libdl.so.2 => /lib/libdl.so.2 (0x006b3000)

vs.

# ldd firefox-bin
linux-gate.so.1 => (0x0051c000)
libpthread.so.0 => /lib/libpthread.so.0 (0x006b9000)
libxul.so => /opt/firefox-3.0b5/libxul.so (0x006d0000)
libmozjs.so => /opt/firefox-3.0b5/libmozjs.so (0x00110000)
libxpcom.so => /opt/firefox-3.0b5/libxpcom.so (0x001a3000)
libplds4.so => /opt/firefox-3.0b5/libplds4.so (0x001a7000)
libplc4.so => /opt/firefox-3.0b5/libplc4.so (0x001aa000)
libnspr4.so => /opt/firefox-3.0b5/libnspr4.so (0x001f9000)
libdl.so.2 => /lib/libdl.so.2 (0x006b3000)