[New-bugs-announce] [issue13979] Automatic *libc.so loading behaviour

[David Goulet]

New submission from David Goulet <dgoulet at efficios.com>:

I'm working with the LTTng (Linux Tracing) team and we came across a problem with our user-space tracer and Python default behaviour. We provide a libc wrapper that instrument free() and malloc() and is usable with a simple LD_PRELOAD.

This lib *was* named "liblttng-ust-libc.so" and we came across python software registering to our trace registry daemon (meaning that somehow the python binary is using our in-process library). We dig a bit and found this:

Lib/ctypes/utils.py:

def _findLib_ldconfig(name):
       # XXX assuming GLIBC's ldconfig (with option -p)
       expr = r'/[^\(\)\s]*lib%s\.[^\(\)\s]*' % re.escape(name)
       res = re.search(expr,
                       os.popen('/sbin/ldconfig -p 2>/dev/null').read())

and, at least, also found in _findLib_gcc(name) and _findSoname_ldconfig(name).

This cause Python to use any library ending with "libc.so" to be loaded....

I don't know the reasons behind this but we are concerned about "future issues" with this kind of behaviour.

Thanks

----------
components: ctypes
messages: 152988
nosy: dgoulet
priority: normal
severity: normal
status: open
title: Automatic *libc.so loading behaviour
type: behavior
versions: Python 2.6, Python 2.7

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue13979>
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