[Crash-utility] Faster iteration on list of struct.field

[Dave Anderson]

----- Original Message -----
> 
> 
> ----- Original Message -----
> > Hi,
> > 
> > I often find myself dumping a bunch of addresses to files to iterate
> > with 'struct_name.field < file_with_addresses', but that is horribly
> > slow for large number of iterations.
> > 
> > `help list` comment for -S vs. -s made me try to use `rd` instead,
> > e.g. get offset manually from `struct -o` then use rd instead like
> > `rd -o xx < addr_list | awk '{ print $2 }' > value_list` -- and that is
> > infinitely better.
> > 
> > 
> > Would it make sense to add a similar option to 'struct' instead so one
> > could do e.g. `struct -S struct_name.field addr` instead of the dance I was
> > doing?
> > (That would require to cache field offset in crash and not query it
> > again everytime, from a quick look at the code, but we could only cache
> > one and still gain a lot for such iterations...)
> > 
> > 
> > Am I missing another more practical way of doing this?
> > (I guess it's not so bad now I came up with using 'rd', but that was
> > non-obvious to me. My use case here involved following a couple of
> > pointers from a list so I dumped the first pointer to follow from list
> > with -S struct1.field1, but then the following iteration just wouldn't
> > end naively)
> 
> Dominique,
> 
> What might make sense is to use the "struct -r" option, which does a raw
> memory dump of a data structure.  But for a reason I do not recall, it
> prevents that option from being used with a "struct_name.field" argument.
> (see line 6628 of symbols.c).  But I don't see why that couldn't be made
> to work, though, since the end result is simply a call to raw_data_dump().
> 
> Dave

...and then if you get "struct -r" to work with a "struct_name.field" 
argument, the next challenge would be the caching aspect of your request.

Currently there's no manner in which command-specific information is
cached beyond the execution of a single command.  With "< file", the
command gets executed from scratch each time. 

Dave