dtrace discuss - Dec 2007 - DTrace & C++ name mangling, an RFC

Hello,

So, as part of the KDE project, I''d like to add dtrace probes to some
of the support libraries such as Qt & the version of the C++ standard
library we''re shipping ( apache/roguewave ).

Unfortunately to support templates, overloading & namespaces C++ requires
name mangling in order to work, so a templated function that takes two arguments
in the global namespace named ''swap'' will end up being called
something like _Z4swapIiEvRT_S1_ , which is utterly meaningless.

So, rather than demangling the function name in the USDT probes I want to add,
I''m considering exploiting the probe name to do this ( not an ideal
scenario, but I can''t think of a better way ).

my current idea is to create a probe name scheme that makes some sort of sense,
and what I came up with is to name the probe like this:
namespace-functionname-[class, if any-]<arg0 type, prefixed with T if
it''s a templated type>-<arg1, as before>...-probe

so a 2-templated argument function in the global namespace named swap would have
probes named global-swap-TT-TT-entry or global-swap-TT-TT-return

this unfortunately doesn''t allow you to do things like trace everything
in blah::function, but given the alternative ( figuring out the function name
that you may not even know because it''s private ) I think it''s
a fairly reasonable compromise

What I''d like to know is if there''s any other issues that I
should be aware of, or if this is just a foolhardy pursuit all over.

Thanks for any comments

-John


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This message posted from opensolaris.org

seems that the name of the probe was stripped by the website... 

namespace-functionname-[class, if any-]-...-probe 
should read
namespace-functionname-[class, if any-]-(arg0 type name, prefixed with T if
it''s templated)-(arg1 type name, similar)...-probe


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This message posted from opensolaris.org

On Tue, Dec 11, 2007 at 12:48:11PM -0800, John Sonnenschein
wrote:
> What I''d like to know is if there''s any other issues that
I should be aware of, or if this is just a foolhardy pursuit all over.
That seems like an entirely reasonable avenue to persue. You may quickly hit
the limit of 64 characters for the probe name. If you do, let us know -- we
can always raise the limit.

Adam

-- 
Adam Leventhal, FishWorks                        http://blogs.sun.com/ahl