Linking to bluetooth library - voluntarily moved from "quick answers" forum

Lost User

I am copying stuff from "quick answers" to here because it is no longer quick solution. I am doing voluntarily and will comment / post in FRONT and if I get discussion going here I will delete "quick answers". Last suggestion was to link to

libbluetooth-dev

Here is the SAME type of error - the library cannot be found. I am deleting most of the post - it is no longer needed.

k5054

You appear to be trying to cross compile a project for a Raspberry Pi from a regular PC. The two CPUS do not share machine language, so you will need to install an arm version of libbluetooth to link against. There was another fellow that was trying to do this with the user name "Vaclav_", who's posts you should be able to search for. I don't know if he ever managed to get the cross comipilation working. In the short term, it might be more productive to develop on the RPI. If you have a RPI-4, then you've got a moderately powerful system. If you convert it to boot from USB using an SSD, it should be powerful and fast enough to get you started, while you research how to get an ARM-compatible libbluetooth installed.

Keep Calm and Carry On

k5054

Part 2: You seem to be using Ubuntu, so you might be able to add packages via the multilib/foreign architecture options for apt. There's a discussion of it in the Debian Wiki here: [Multiarch/HOWTO - Debian Wiki](https://wiki.debian.org/Multiarch/HOWTO) I haven't tried this, so can't say for certain it will work, but if it does, it will be much easier than having to cross compile the libraries yourself.

Keep Calm and Carry On

Lost User

Sorry about the long post - I have one more problem. I installed libbluetooth-dev on my ARM /RPi OS , used csp to copy to my X86 PC verified it exist on PC added -L to my options Still getting same error BUT the linker error is coming from different path and it definitely looks as the linker is NOT looking to the path I added

-L/usr/lib/arm-linux-gnueabihf/arm-linux-gnueabihf' '-L/usr/lib/arm-linux-gnueabihf' '

, but it is in verbose output Still missing something...

OLLECT_GCC_OPTIONS='-L/usr/lib/x86_64-linux-gnu' '-L/usr/lib/arm-linux-gnueabihf/arm-linux-gnueabihf' '-L/usr/lib/arm-linux-gnueabihf' '-v' '-o' 'RPI_Bluetooth' '-shared-libgcc' '-march=armv6' '-mtune=arm1176jz-s' '-mfloat-abi=hard' '-mfpu=vfp' '-mtls-dialect=gnu'
/home/qw/tools/arm-bcm2708/gcc-linaro-arm-linux-gnueabihf-raspbian-x64/bin/../libexec/gcc/arm-linux-gnueabihf/4.8.3/collect2 --sysroot=/home/qw/tools/arm-bcm2708/gcc-linaro-arm-linux-gnueabihf-raspbian-x64/bin/../arm-linux-gnueabihf/libc --build-id --eh-frame-hdr -dynamic-linker /lib/ld-linux-armhf.so.3 -X -m armelf_linux_eabi -o RPI_Bluetooth /home/qw/tools/arm-bcm2708/gcc-linaro-arm-linux-gnueabihf-raspbian-x64/bin/../arm-linux-gnueabihf/libc/usr/lib/arm-linux-gnueabihf/crt1.o /home/qw/tools/arm-bcm2708/gcc-linaro-arm-linux-gnueabihf-raspbian-x64/bin/../arm-linux-gnueabihf/libc/usr/lib/arm-linux-gnueabihf/crti.o /home/qw/tools/arm-bcm2708/gcc-linaro-arm-linux-gnueabihf-raspbian-x64/bin/../lib/gcc/arm-linux-gnueabihf/4.8.3/crtbegin.o -L/usr/lib/x86_64-linux-gnu -L/usr/lib/arm-linux-gnueabihf/arm-linux-gnueabihf -L/usr/lib/arm-linux-gnueabihf -L/home/qw/tools/arm-bcm2708/gcc-linaro-arm-linux-gnueabihf-raspbian-x64/bin/../lib/gcc/arm-linux-gnueabihf/4.8.3 -L/home/qw/tools/arm-bcm2708/gcc-linaro-arm-linux-gnueabihf-raspbian-x64/bin/../lib/gcc/arm-linux-gnueabihf -L/home/qw/tools/arm-bcm2708/gcc-linaro-arm-linux-gnueabihf-raspbian-x64/bin/../lib/gcc -L/home/qw/tools/arm-bcm2708/gcc-linaro-arm-linux-gnueabihf-raspbian-x64/bin/../lib/gcc/arm-linux-gnueabihf -L/home/qw/tools/arm-bcm2708/gcc-linaro-arm-linux-gnueabihf-raspbian-x64/bin/../lib/gcc/arm-linux-gnueabihf/4.8.3/../../../../arm-linux-gnueabihf/lib -L/home/qw/tools/arm-bcm2708/gcc-linaro-arm-linux-gnueabihf-raspbian-x64/bin/../arm-linux-gnueabihf/libc/lib/arm-linux-gnueabihf -L/home/qw/tools/arm-bcm2708/gcc-linaro-arm-linux-gnueabihf-raspbian-x64/bin/../arm-linux-gnueabihf/libc/lib -L/home/qw/tools/arm-bcm2708/gcc-linaro-arm-linux-gnueabihf-raspbian-x64/bin/../arm-linux-gnueabihf/libc/lib

k5054

Firstly:

OLLECT_GCC_OPTIONS='-L/usr/lib/x86_64-linux-gnu'

That's a bit odd. If you are compiling for arm, you should not be including anything from the x86_64 lib tree. Secondly you seem to be confusing the difference between a software package, and its contents. The package is libbluetooh-dev. It has headers, documentation and other files that are needed to compile a program that uses libbluetooth. The package libbluetooth3 contains the shared library: /usr/lib/arm-linux-gnueabihf/libbluetooth.so.3.xx.yy, so you should ask to link only with -lbluetooth Thirdly: if you've installed the gcc cross-copmiler tools correctly, it should know how to find libm without any additional help from you. Consider the following very simple program

#include
#include

int main()
{
printf("%f\n", lgamma(2.0));

return 0;

}

In order to compile it, we need to include libm. On my X86-64 computer I do

gcc example.c -o example -lm

to create an x86-64 executable program. To create an ARM version I do

gcc-arm7 example.c -o example-arm -lm

I now have 2 versions of the example program, one for X86-64 and one for ARM e.g.

k5054@loaclhost $ file example example-arm
example: ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, BuildID[sha1]=c5d319f4b896ad825b708ff73a248ed23f64489f, for GNU/Linux 3.2.0, not stripped
example-arm: ELF 32-bit LSB shared object, ARM, EABI5 version 1 (SYSV), dynamically linked, interpreter /lib/ld-linux-armhf.so.3, BuildID[sha1]=1bc8369c7de09a7510c93c0bcab5824c6342d688, for GNU/Linux 3.2.0, not stripped

Are you sure you've installed the cross compiler correctly and can produce simple programs (like example.c above or a basic hello world) that can run on the RPI?

Keep Calm and Carry On

Lost User

1. Being lazy I left the x86 links references in - it should not matter, but I'll take them out. 2. Yes I got puzzled by instruction to "install a library " when in essence I was installing a Linux package which contains the library and other stuff. I got better undertaking of thet now. 3. I have another app in works with no problem crosscompiling and actually running it on Raspberry. 3. No, I did not physically install the crosscomplier - just selected "cross compile" option in Eclipse. I am not sure if my -l and -L options are syntactically correct - but it looks OK in output I'll recheck that . Many thanks for your help, appreciate that very much.

Lost User

Update 1. installing libbluetooth-dev package installs libbluetooth.a and libbluetooth.so AKA there is NO libbluetooth-dev library 2. linker options are -l:libbluetooth.a -L/usr/lib/x86_64-linux-gnu build process links and application runs as local , no crosscompiler, on "host" PC pre lang="text"> Building target: TEST_BT Invoking: GCC C++ Linker g++ -L/usr/lib/x86_64-linux-gnu -v -o "TEST_BT" ./src/TEST_BT.o -l:libbluetooth.a Using built-in specs. COLLECT_GCC=g++ Can anybody educate me about the ":" in -l**:**libbluetooth.a. I ADDED it in Eclipse options. WHY ?

Lost User

Member 14968771 wrote:

Can anybody educate me about the ":" in -l:libbluetooth.a.

I cannot find any reference to that option in Using the GNU Compiler Collection (GCC): Link Options[^], where the normal option would be -lbluetooth. I can only assume it is an add-on from somewhere that allows yo to specify the full library name.

Lost User

It definitely looks as a linker "suggestion " when "libbluetooth" is set as an option When both ":" and ".a" are used linker does not complain. /usr/bin/ld: cannot find -llibbluetooth /usr/bin/ld: note to link with /usr/lib/x86_64-linux-gnu/libbluetooth.a use -l:libbluetooth.a or rename it to liblibbluetooth.a collect2: error: ld returned 1 exit status