Convert Static Lib to Dynamic

Question

I have a libsomething.a file which is a static library with all dependencies included.

I need to be able to import this in Python as it is a Python C library. According to this, it is not possible to use a static library as a CPython library.

How can I take my .a file and make it a .so, keeping all static dependencies baked in?

Background: I am using Crowbar to build a CPython shared library which can be called from Python in AWS Lambda. Until now, it has worked flawlessly, but as soon as I added in dependencies which require OpenSSL, I get linker problems when running the code in Lambda.

The issue here is that the Amazon Linux image that is used to execute code has an ancient OpenSSL version. I have recreated the runtime environment, but the issue is that the old version of OpenSSL no longer exists in Amazon's yum repository. This means that installing openssl-devel pulls down OpenSSL 1.0.2k, where in the runtime the version of OpenSSL provided is 1.0.1.

This results in linking failing at runtime in Lambda. Therefore, I need a way to build a (mostly) statically linked shared library. The only shared libraries I want my SO to link from are libc and the kernel, with everything else statically compiled in.

In the Lambda execution environment, LD_LIBRARY_PATH is set to /usr/lib64:/lib64:./lib, so anything in the lib folder will be loaded, but only as a last result, and if I link against OpenSSL, I get the wrong version every time.

In Rust, I have the option of producing liblambda.a or liblambda.so, a static or a shared library. I'm assuming that producing a *.a and then converting into a shared library only linking to glibc and kernel dependencies.

How have you got that library? What is it doing? – Basile Starynkevitch Mar 13 '18 at 18:12 — Basile Starynkevitch, Mar 13 '18 at 18:12

Basile Starynkevitch · Answer 1 · 2018-03-13T18:18:58.887

3

No, you cannot do that conversion from static library to shared one (at least not in practice). Read How To Write Shared Libraries by Drepper.

One of the main reason is that shared libraries want (that it nearly need) to have position independent code (which static libraries usually don't have).

However, on Linux most libraries are free software. So why don't you recompile your library from source code into a shared library?

^{(you might perhaps recompile that specific version of OpenSSL from source)}

edited Mar 13 '18 at 18:18

answered Mar 13 '18 at 18:09

Basile Starynkevitch

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I have updated my question with more info about my build environment and the specific case in which things are going wrong. – Naftuli Kay Mar 13 '18 at 18:14
I'm trying to [find a workaround within `rustc` and `cargo`](https://stackoverflow.com/questions/49263452/static-link-specific-library-to-shared-library). – Naftuli Kay Mar 13 '18 at 18:33
PIC is not a language issue. – Basile Starynkevitch Mar 13 '18 at 18:35

Convert Static Lib to Dynamic

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