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List:       fedora-devel-list
Subject:    Re: Fedora 32 System-Wide Change proposal: Build Python 3 to statically link with libpython3.8.a for
From:       Florian Weimer <fweimer () redhat ! com>
Date:       2019-11-17 16:29:39
Message-ID: 87k17y79fw.fsf () oldenburg2 ! str ! redhat ! com
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* John Reiser:

> On 2019-11-15 at 14:51 UTC, David Malcolm wrote:
>
>> Thinking aloud: does anyone ever use symbol overriding for anything
>> other than glibc?
>
> Yes.  It is particularly useful for "spear fishing" debugging of lower-level
> interfaces in large, complex multi-process applications.  By some means
> you determine that [part of] the bug involves a bad parameter to
> a particular API, but a conditional breakpoint in gdb has too much overhead
> (if you can figure out at all how to invoke gdb in the cloud of processes.)
> So: LD_PRELOAD a .so which overrides the API and checks the parameter.
> If no problem then pass control to the original implementation via RTLD_NEXT.
> If bad, then raise an alarm, prepare a backtrace, pause or spin until
> rescued by manual attach of gdb, etc.

That only seems to need shallow interposition, though.  In most cases, I
doubt you are interested in API calls from the library self because
those are probably unproblematic.

Thanks,
Florian
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