[Python-Dev] ctypes/utils.py problem

[David Goulet]

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Hi everyone,

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

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"
that can occur with this kind of behavior.

For now, we renamed our lib so everything is fine.

Thanks a lot guys.
David
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