Question

I want to replace libsqlite3 with the special version for Python.
I have a special version of libsqlite3.so.0 /path/to/libsqlite3.so.0 and configured LD_LIBRARY_PATH.
However, python’s internal will not load it.

I checked and noticed the following:

1. import sqlite3 loads python’s original /usr/lib/python2.7/sqlite/__init__.py and dbapi2.py.
2. dbapi2.py imports _sqlite, and this indicates /usr/lib/python2.7//lib-dynload/_sqlite3.so.
3. _sqlite3.so always loads /usr/lib/i386-linux-gnu/libsqlite3.so.0, in spite of setting LD_LIBRARY_PATH.
4. If I copy libpthread.so.0 to /path/to/libpthread.so.0, _sqlite3.so loads it. So, /path/to/libpthread.so.0 is loaded but /path/to/libsqlite3.so.0 is not loaded.

I want to know how to load /path/to/libsqlite3.so.0, a special version, without replacing /usr/lib/i386-linux-gnu/libsqlite3.so.0 (only with non-privileged permission).

Answer 1

You might try to force loading of the lib with:

LD_PRELOAD=/path/to/libsqlite3.so.0 python ...

The library will be loaded in memory when python will be executed. So normally when _sqlite3 module will be imported, it will not load libsqlite3.so.0, and use the version already preloaded in memory.

Edit

The LD_LIBRARY_PATH doesn’t work in that case cause libsqlite3.so.0 is loaded by _sqlite.so module, loaded by dlopen() within Python. In that case, the manpage of dlopen() said that the order is:

1. (ELF only) If the executable file for the calling program contains a DT_RPATH tag, and does not contain a DT_RUNPATH tag, then the directories listed in the DT_RPATH tag are searched.

2. If, at the time that the program was started, the environment variable LD_LIBRARY_PATH was defined to contain a colon-separated list of directories, then these are searched. (As a security measure this variable is ignored for set-user-ID and set-group-ID programs.)

3. …

So if an DT_RPATH is set on the binary, it will be taken prior to your LD_LIBRARY_PATH.