[Bug translator/7053] New: automatic global printing of statistic needs to check @count>0

[Bug translator/7053] New: automatic global printing of statistic needs to check @count>0

[fche at redhat dot com]

probe never {p <<< 1} global p
results in 
   ERROR: empty aggregate near identifier 'p' at <input>:1:28
but should result in
   p @count=0x0

-- 
           Summary: automatic global printing of statistic needs to check
                    @count>0
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: translator
        AssignedTo: systemtap at sources dot redhat dot com
        ReportedBy: fche at redhat dot com


http://sourceware.org/bugzilla/show_bug.cgi?id=7053

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[Bug translator/7053] automatic global printing of statistic needs to check @count>0

[wenji dot huang at oracle dot com]

------- Additional Comments From wenji dot huang at oracle dot com  2008-11-27 04:46 -------
The related code in tranlate.cxx

// PR 2142+2610: empty aggregates

3757       o->newline() << "if (unlikely (" << agg.value() << " == NULL)"

3758                    << " || " <<  agg.value() << "->count == 0) {";

3759       o->newline(1) << "c->last_error = \"empty aggregate\";";

3760       o->newline() << "goto out;";

I can't reproduce 2142 and 2610 when such code is commented. Then
sensible result will be printed in the test case. Maybe some 
improvements on global were added since that commit.

Guess we can weaken the checking of empty aggregrate.



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[Bug translator/7053] automatic global printing of statistic needs to check @count>0

[fche at redhat dot com]

------- Additional Comments From fche at redhat dot com  2008-11-27 16:32 -------
If we wish to keep the status quo that @operators on empty aggregates are
erroneous, then the code to change for this bug would be elaborate.cxx's
synthesis of the printf (" @count=....@avg=..."), to fork it into one
case where @count=0 and is printed alone, and another one where @count>1
and the other @values are printed.


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[Bug translator/7053] automatic global printing of statistic needs to check @count>0

[wenji dot huang at oracle dot com]

------- Additional Comments From wenji dot huang at oracle dot com  2008-12-02 03:35 -------
Created an attachment (id=3085)
 --> (http://sourceware.org/bugzilla/attachment.cgi?id=3085&action=view)
patch for checking empty aggregate and adding default print

Add checking empty aggregate and default print where @count==0. It's not
necessary to check empty aggregate in Array case. The generated foreach 
can eliminate the possibly of printing empty aggregate.

Sample script:
$ sudo stap -ve 'global var; probe never{ var<<<2}' -p2
Pass 1: parsed user script and 47 library script(s) in 540usr/60sys/603real ms.

# globals
var:stats
# probes
never /* <- never */
(var) <<< (2)
end /* <- end */
{
if ((@count(var)) > (0)) printf("var @count=%#x @min=%#x @max=%#x @sum=%#x
@avg=%#x\\n", @count(var), @min(var), @max(var), @sum(var), @avg(var))
else printf("var @count=0x0\\n")

}
Pass 2: analyzed script: 2 probe(s), 0 function(s), 0 embed(s), 1 global(s) in
10usr/20sys/26real ms.


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[Bug translator/7053] automatic global printing of statistic needs to check @count>0

[fche at redhat dot com]

------- Additional Comments From fche at redhat dot com  2008-12-02 19:17 -------
Nice work, plase commit with a test case.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|systemtap at sources dot    |wenji dot huang at oracle
                   |redhat dot com              |dot com
             Status|NEW                         |ASSIGNED


http://sourceware.org/bugzilla/show_bug.cgi?id=7053

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