Re: [PATCH v2] gdb: split array and string limiting options

[Simon Sobisch <simonsobisch@web.de>]

 > From: Andrew Burgess <andrew.burgess@embecosm.com>
 >
 > This commit splits the set/show print elements options into two.  We
 > retain set/show print elements for controlling how many elements of an
 > array we print, but a new set/show print characters is added which is
 > used for controlling how many characters of a string are printed.
 > [...]
Reference to the full patch:
https://sourceware.org/pipermail/gdb-patches/2021-December/184467.html


I really like the general idea and would like to see this added, but I
think the patch goes too far and will break both old and new usage.

In my opinion there should be only 1 new test for the new setting and
the other should be left unchanged while still working, because then
existing usages will still work, too.

To do so the new parameter cannot be directly used as it is in the patch
but must be fowarded to a new function or duplicated.

As an example this would mean instead of :

--- src.orig/gdb/c-valprint.c
+++ src/gdb/c-valprint.c
@@ -271,7 +271,7 @@ c_value_print_array (struct value *val,

     for (temp_len = 0;
  	   (temp_len < len
-	    && temp_len < options->print_max
+	    && temp_len < options->print_max_chars
  	    && extract_unsigned_integer (valaddr + temp_len * eltlen,
  					 eltlen, byte_order) != 0);
  		   ++temp_len)

have the following


+   const int print_max_chars = (options->print_max_chars != -1) ?
options->print_max_chars : options->print_max;
     for (temp_len = 0;
  	   (temp_len < len
-	    && temp_len < options->print_max
+	    && temp_len < print_max_chars
  	    && extract_unsigned_integer (valaddr + temp_len * eltlen,
  					 eltlen, byte_order) != 0);
  		   ++temp_len)


This effectively means that until you explicit set the new "print
characters" the existing "print elements" setting will be used, and if
you "set print characters off" (or similar, that would internally
resolve to -1) you get the length depending on "print elements" again.

The parameter type in python for "print elements" is (guessed)
gdb.PARAM_UINTEGER, the type for "print characters" would be
gdb.PARAM_INTEGER with -1 meaning "take the other parameter".


If those changes are done there is no breakage whatever which could also
speedup the inclusion s it hopefully lands in GDB 11.2.

Simon