[Crash-utility] Speed up list/tree '-s' output.

[Dave Anderson]

Hi Alexandr,

I'm still testing and sanity-checking the symtab.c patch given that it's
modifying such a commonly-called function.  Interestingly enough, it's
actually uncovered a bug with the current determination of the page.list 
members, which I found by saving the output of "help -o" into a file, 
both without and then with your patch, into /tmp/old and /tmp/new, and 
then diff'ed the two files:

  # diff /tmp/old /tmp/new
  221,223c221,223
  <                      page_list: -1
  <                 page_list_next: -1
  <                 page_list_prev: -1
  ---
  >                      page_list: 32
  >                 page_list_next: 32
  >                 page_list_prev: 40
  #

Fortunately those fields aren't used by the crash code for more recent
kernels, which have gone crazy with the anonymous structures in the page
structure.  But anyway, that was a good catch by your patch.

On the other hand, I don't like the use of the deep and offset static
variables, because there's always the remote possibility that a
CTRL-C or other function failure may happen while they are set, and
then leave them in a bogus state.  So I would rather they get passed as
arguments.

Thanks,
  Dave



----- Original Message -----
> Hi Dave,
> 
> here is updated patch for gdb/symtab.c:
> 
> --- gdb-7.6.orig/gdb/symtab.c	2016-08-18 09:06:33.000000000 +0300
> +++ gdb-7.6/gdb/symtab.c	2016-08-23 14:28:45.456510348 +0300
> @@ -5486,13 +5486,15 @@
>  	struct field *nextfield;
>  	short nfields;
>  	struct type *typedef_type;
> +	static int deep = 0;
> +	static long offset = 0;
>  
>  	req->member_offset = -1;
>  
>  	nfields = TYPE_MAIN_TYPE(type)->nfields;
>  	nextfield = TYPE_MAIN_TYPE(type)->flds_bnds.fields;
>  
> -        if (nfields == 0) {
> +	if (nfields == 0 && deep == 0 /* The first call */) {
>  		struct type *newtype;
>                  newtype = lookup_transparent_type(req->name);
>                  if (newtype) {
> @@ -5505,13 +5507,21 @@
>  
>  	for (i = 0; i < nfields; i++) {
>  		if (STREQ(req->member, nextfield->name)) {
> -			req->member_offset = nextfield->loc.bitpos;
> +			req->member_offset = offset + nextfield->loc.bitpos;
>  			req->member_length = TYPE_LENGTH(nextfield->type);
>  			req->member_typecode = TYPE_CODE(nextfield->type);
>  			if ((req->member_typecode == TYPE_CODE_TYPEDEF) &&
>  			    (typedef_type = check_typedef(nextfield->type)))
>          			req->member_length = TYPE_LENGTH(typedef_type);
>  			return;
> +		} else if (*nextfield->name == 0) { /* Anonymous struct/union */
> +			deep++;
> +			offset += nextfield->loc.bitpos;
> +			get_member_data(req, nextfield->type);
> +			offset -= nextfield->loc.bitpos;
> +			deep--;
> +			if (req->member_offset != -1)
> +				return;
>  		}
>  		nextfield++;
>  	}
> @@ -5705,7 +5715,7 @@
>  		req->target_length = target_type->length;
>  	}
>  
> -	if (req->member)
> +	if (req->member)
>  		get_member_data(req, type);
>  
>          do_cleanups (old_chain);
> 
> The patch for crash tool can be found on github:
> https://raw.githubusercontent.com/hziSot/crash-patches/41abc6f9c91c2a602973ff9564234395deadb80e/crash_speed_up_tree_list.patch
> 
> Thanks,
> Alexandr
> 
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