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I have a buildroot project in which I want to add a library compiled with pascal. The reason for this is that it is a custom library and porting it to C is too much work at this point. I am compiling it for a raspberry pi CM3. How it currently works:

  1. I have compiled the library libcustom.so on an raspberry pi (raspbian).
  2. In buildroot I download the library from a git repository.

Now the problem I have is that the program that used this library cannot find the library (although it is in the /usr/lib/ folder). Using the ldd command I got the following output:

$ ldd /usr/lib/libcustom.so
checking sub-depends for 'not found'
checking sub-depends for 'not found'
checking sub-depends for 'not found'
    ld-linux-armhf.so.3 => not found (0x00000000)
    libdl.so.2 => not found (0x00000000)
    libc.so.6 => not found (0x00000000)
    not a dynamic executable

By checking the output given by the same command on the system where I compiled the library helped me to resolve which sub-depends were missing. Since the architecture of both the systems is the same I figured that to test what is missing I could simply copy the libraries from the compilation system to the buildroot system. (libraries that were missing were libc.so.6,libdl.so.2 and lib-linux-armhf.so.3). Now ldd gives me the following:

$ ldd /usr/lib/libcustom.so
checking sub-depends for '/lib/ld-linux-armhf.so.3'
checking sub-depends for '/usr/lib/libdl.so.2'
checking sub-depends for '/usr/lib/libc.so.6'
    /lib/ld-linux-armhf.so.3 (0x76fc2000)
    linux-vdso.so.1 (0x7ef00000)
checking sub-depends for '/usr/lib/libc.so.6'
    /lib/ld-linux-armhf.so.3 (0x76ee8000)
    linux-vdso.so.1 (0x7efeb000)
    /lib/ld-linux-armhf.so.3 => /lib/ld-linux-armhf.so.3 (0x00000000)
    libc.so.6 => /usr/lib/libc.so.6 (0x00000000)
    /lib/ld-linux-armhf.so.3 => /lib/ld-linux-armhf.so.3 (0x00000000)

The custom library is still not working (and the ldd still points to empty (0x00000000) libraries.

I have been searching around a bit however there are still two things that I do not understand:

  1. Why is the above solution not working? The libraries are the same architecture but as ldd points out above, some libraries still cannot be properly found.
  2. How can I include libraries in buildroot? I have been searching for this and found how to add custom packages, but I am still clueless about how to add specific libraries (such as the one I have added by hand).
Steven
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2 Answers2

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You can't take a library built on system A (Raspbian) and automagically expect this library to work on system B (built with Buildroot). Indeed the C library may be different, and the ABI may be different. Compatibility at the binary level is not trivial.

You've got two options here:

  • Make sure the Buildroot configuration matches the libc/ABI used on Raspbian. In your case, it seems like building a glibc toolchain in Buildroot with the EABIhf ABI should do the trick.

  • Build your library with Buildroot. That will require creating a package for a Pascal cross-compiler, and then a package for your library.

Thomas Petazzoni
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  • Hmm, the second option that you provide seems to be the most robust option because that makes the final configuration independent of the Raspbian configuration. This means that I do have to implement the pacakage for the Pascal cross compiler . As far as I am aware this is not yet included in the buildroot as a package. Are you aware of some documentation that could help me on the way to implement this? – Steven Jul 02 '18 at 15:15
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Is the distribution of both systems the same? Otherwise attempt to build the library cross with libraries from target.

Marco van de Voort
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  • I don't know how to add specific libraries to buildroot. The ones I need are not included be default. – Steven Jun 26 '18 at 07:03