What is causing sprof to complain about “inconsist

问题:

I'm trying to use sprof to profile some software (ossim) where almost all the code is in a shared library. I've generated a profiling file, but when I run sprof, I get the following error:

> sprof /home/eca7215/usr/lib/libossim.so.1 libossim.so.1.profile -p > log
Inconsistency detected by ld.so: dl-open.c: 612: _dl_open: Assertion `_dl_debug_initialize (0, args.nsid)->r_state == RT_CONSISTENT' failed!

The instructions I was following said that I needed libc version at least 2.5-34, I have libc version 2.12.2 (Gentoo, kernel 2.6.36-r5).

I can't find any explanation as to what the error means or (more interestingly) how to fix it, the only half-relevant google results are for a bug in an old version of Skype.

回答1:

I got a bit curious since this is still broken in OpenSuse 12.x. I would have thought a bug originally reported in '09 or so would have been fixed by now. I guess nobody really uses sprof. (or maybe dl-open is so fragile that people are scared to touch it :-)

The issue boils down to the __RTLD_SPROF flag used as argument to dlopen. Take any simple program that calls dlopen, or that flag to the second arg and you get the same failed assertion. I used the sample program at the bottom of http://linux.die.net/man/3/dlopen as an example

handle = dlopen(argv[1], RTLD_LAZY | __RTLD_SPROF);

From what I can tell from a quick look at dl-open.c, this flags short circuits some of what dl_open does. So the r_flag specified in the assertion doesn't get set to RT_CONSISTENT.