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Re: [pcp] Multi-archive Contexts: Some PCP Tools Lost in Time

To: pcp@xxxxxxxxxxx
Subject: Re: [pcp] Multi-archive Contexts: Some PCP Tools Lost in Time
From: Marko Myllynen <myllynen@xxxxxxxxxx>
Date: Wed, 17 Feb 2016 08:49:13 +0200
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In-reply-to: <y0mio1o9s7y.fsf@xxxxxxxx>
Organization: Red Hat
References: <56C3608E.9090404@xxxxxxxxxx> <y0mvb5oa323.fsf@xxxxxxxx> <56C37828.10007@xxxxxxxxxx> <20160216194348.GC2398@xxxxxxxxxx> <56C395AF.1030306@xxxxxxxxxxxxxxxx> <y0mio1o9s7y.fsf@xxxxxxxx>
Reply-to: Marko Myllynen <myllynen@xxxxxxxxxx>
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.5.0
Hi,

On 2016-02-17 00:59, Frank Ch. Eigler wrote:
> kenj wrote:
>> [...]
>> I think all of
>> - pmlogdump
>> - pmlogcheck
>> - pmlogrewrite
>> should / could be constrained to operate on a single archive at a time.
>> [...]
> 
> (Yeah, maybe.)
> 
>> Would that make life easier?
> 
> Not sure; I'll defer to brolley for the more definitive word.  But
> from first principles, one problem here is that the libpcp ABI
> includes -some- data structure definitions, like _pmContext and its
> connected bits.  Old binaries that traverse those data structures were
> compiled against a previous <impl.h>, and could crash or whatever if
> run against libpcp.so that has the changes -- whether or not they
> happen to be operating on a multi-archive.
> 
> It sounds likely that the apps that rely on impl.h internals (why is
> that file installed anyway?) may be the same ones that that we can
> detect & disable with a symbol-versioning hack such as a dummy 
> __pmHandleToPtr() { return 0; } function.

Is symbol versioning available on all supported platforms?

Thanks,

-- 
Marko Myllynen

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