[Bug translator/11096] New: Getting global module vars in functions

[Bug translator/11096] New: Getting global module vars in functions

[mjw at redhat dot com]

It is often convenient to grab a global variable value in a function. But
currently you cannot do that, so you have to grab it in a probe handler and
store it globally or pass it to the function invocation (then you can use the
address of this variable and @cast(var "struct", "module") to extract the
information in the function).

Possible syntax: @global($var, "module")

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           Summary: Getting global module vars in functions
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: translator
        AssignedTo: systemtap at sources dot redhat dot com
        ReportedBy: mjw at redhat dot com


http://sourceware.org/bugzilla/show_bug.cgi?id=11096

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[Bug translator/11096] Getting global module vars in functions

[jistone at redhat dot com]

------- Additional Comments From jistone at redhat dot com  2009-12-16 19:48 -------
Global vars that are in scope should be usable already.  Are you talking about
globals that are only present in other CUs?

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http://sourceware.org/bugzilla/show_bug.cgi?id=11096

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[Bug translator/11096] Getting global module vars in functions

[mjw at redhat dot com]

------- Additional Comments From mjw at redhat dot com  2009-12-16 20:55 -------
(In reply to comment #1)
> Global vars that are in scope should be usable already.

But in a function there is no scope, so no variable is accessible.

The use case for me is the jstack() function, that would benefit from having
access to some of the globals in libjvm.so. Currently we have a probe on vm_init
to collect those globals and store them for later use in the function. But that
is somewhat limiting the use of the jstack() function (it can only be used after
some probe in the libjvm.so context has been fired first).

-- 


http://sourceware.org/bugzilla/show_bug.cgi?id=11096

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[Bug translator/11096] Getting global module vars in functions

[jistone at redhat dot com]

------- Additional Comments From jistone at redhat dot com  2009-12-16 22:54 -------
I clarified my confusion with mjw on IRC -- in my response I was thinking of
probes on a C function that access global variables, which should work fine.  He
is talking about a stap function (with no $ context) that wants to access a
module's global variables.

-- 


http://sourceware.org/bugzilla/show_bug.cgi?id=11096

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[Bug translator/11096] Getting global module vars in functions

[fche at redhat dot com]

------- Additional Comments From fche at redhat dot com  2010-05-21 19:43 -------
*** Bug 4906 has been marked as a duplicate of this bug. ***

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http://sourceware.org/bugzilla/show_bug.cgi?id=11096

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