[SOLVED] Linking custom libraries with g++ and cross compilation

mr.simo · 11-04-2014, 03:46 AM

I know linking external custom libraries can be painfull and in fact it is..

I have sombe libraries wich I have to use in my next program, I am trying do link these libraries but nothing works fine.

First of all I am compiling from an x86 with arm-none-linux-gnueabi (installed into /opt/arm/) , so I will have to move the binaries to another machines. The standard process works always fine for Linux system binaries.

On my x86 system I have copied the custom library binaries into

Code:

/opt/arm/arm-none-linux-gnueabi/libc/lib/customLibs/

, and into **/usr/lib/**into the ARM system.

Then I copied the header files into

Code:

/opt/arm/arm-none-linux-gnueabi/libc/usr/include/customLibs/

on the x86 system and then into **/usr/inlcude** on the ARM system, as I did for the library binaries.

When I compile with make on the x86 machine, I execute:

Code:

arm-none-linux-gnueabi-g++ main.cc -o main -I /opt/arm/arm-none-linux-gnueabi/libc/usr/include/customLibs -L /opt/arm/arm-none-linux-gnueabi/libc/lib/customLibs -l /opt/arm/arm-none-linux-gnueabi/libc/lib/customLibs/customLib.so

and I got

Code:

/opt/arm/bin/../lib/gcc/arm-none-linux-gnueabi/4.8.3/../../../../arm-none-linux-gnueabi/bin/ld: cannot find -l/opt/arm/arm-none-linux-gnueabi/libc/lib/customLibs/customLib.so
collect2: error: ld returned 1 exit status
make: *** [main] Error 1

However the library is into the path...

What's wrong with my command line arguments ?
Thank you in advance.

norobro · 11-04-2014, 09:03 AM

From man ld:

Quote:

-l namespec
--library=namespec
Add the archive or object file specified by namespec to the list of files to link. This
option may be used any number of times. If namespec is of the form :filename, ld will search
the library path for a file called filename, otherwise it will search the library path for a
file called libnamespec.a.

If your library is named customLib.so use:

Code:

-l:customLib.so

If it is named libcustomLib.so you can use:

Code:

-lcustomLib

mr.simo · 11-05-2014, 07:10 AM

Hi norobro,

Thank you for your response.

I already done that, it works better, but it seems that when I try to compile, a lot of files are not encountered..
I will explain better the situation.

There are various binary files of this shared libraries, totally 10, but this is irrelevant I think, let's name them libcustom.so to libcustom10.so.

As I putted the binary .so files into

Code:

/usr/lib/customLib

and into

Code:

/usr/lib

with symbolic link from

Code:

/usr/lib/customLib

to its parent directory.

Now, when I try to execute:

Code:

arm-angstrom-linux-gnueabi-g++ file.cc -o file -L /usr/lib/customLibs -lcustom1 -lcustom2 -lcustom3 -lcustom4 -lcustom5 -lcustom6 -lcustom7 -lcustom8 -lcustom9 -lcustom10 -lpthread -ldl -lrt

linking the libs in order (because I have to respect a determine order) it compiles but the compiler warns about some of these libraries are missing others, i.e. libcustom3.so misses libcustom2.so etc. It seems the compiler cannot find the libs...

Then when I execute I get this error:

Code:

./file: error while loading shared libraries: libcustom3.so: cannot open shared object file: No such file or directory

libcustom3.so is the first lib the compiler cannot find during compilation process.

LD_LIBRARY_PATH is

Code:

echo $LD_LIBRARY_PATH
/usr/lib:/usr/lib/trimble:/lib

I am a little bit confused...

mr.simo · 11-05-2014, 09:50 AM

Problem solved.

The libraries were not linked in the properly order, because who gave me these libs did not specify the correct order...

I solved the order by "reverse engineering".