dtrace discuss - Jul 2009 - Can't print stack traces if printa has a format string?

Hi all,

Is there a way to print stack traces as part of an aggregation key in 
dtrace? I''m trying to count occurrences of different stack traces, but 
my program has lots of indirect function calls and the output of stack() 
often doesn''t contain the current function. Aggregating on 
@who[caller,stack()] should fix this in theory, but I can''t get the 
printing to work right.

printa(@who) shows the stack but just an address for caller, and neither 
%a nor %s allows me to print a stack trace if I give printa a format
string:
> printa("%40a %40s %@d", @who)
> dtrace: failed to compile script who.d: line 30: printa( ) argument #3 
> is incompatible with conversion #2 prototype:
>         conversion: %s
>          prototype: char [] or string (or use stringof)
>           argument: stack
>
> printa("%40a %40a %@d", @who)
> dtrace: failed to compile script who.d: line 30: printa( ) argument #3 
> is incompatible with conversion #2 prototype:
>         conversion: %a
>          prototype: pointer or integer
>           argument: stack
On a related note, it seems that "%A" can translate user-level
addresses
to symbols in a printf/printa, which is not documented AFAICT and has 
caused me pain in the past (see 
http://kr.sun.com/developers/solaris/techdocs/dtrace_tips_public.pdf)

Ideas?
Ryan

Ryan Johnson wrote:
> Is there a way to print stack traces as part of an aggregation key in 
> dtrace? I''m trying to count occurrences of different stack traces,
but
> my program has lots of indirect function calls and the output of 
> stack() often doesn''t contain the current function. Aggregating on
> @who[caller,stack()] should fix this in theory, but I can''t get
the
> printing to work right.
Ah! Turns out this question was already asked in 2005, and the answer is 
"%k"
> On a related note, it seems that "%A" can translate user-level 
> addresses to symbols in a printf/printa, which is not documented 
> AFAICT and has caused me pain in the past (see 
> http://kr.sun.com/developers/solaris/techdocs/dtrace_tips_public.pdf)
I''ve updated the printf/printa wiki page to mention both %A and %k.

Ryan