list.exp: Catch "set listsize" failures (and "set listsize -1/0"'s history).

Before the changes starting at
http://sourceware.org/ml/gdb-patches/2012-08/msg00020.html, the 'set
listsize' command only accepted "0" as special value, meaning
"unlimited".  The testsuite actually tried "set listsize -1" and
expected that to mean unlimited too.

If you tried testing list.exp at the time of that patch above,
you'd get:

  (gdb) PASS: gdb.base/list.exp: list line 10 with listsize 100
  set listsize 0
  (gdb) PASS: gdb.base/list.exp: setting listsize to 0 #6
  show listsize
  Number of source lines gdb will list by default is unlimited.
  (gdb) PASS: gdb.base/list.exp: show listsize unlimited #6
  list 1
  1       #include "list0.h"
  2
  ...
  42          /* Not used for anything */
  43      }
  (gdb) PASS: gdb.base/list.exp: listsize of 0 suppresses output
  set listsize -1
  integer 4294967295 out of range
  (gdb) PASS: gdb.base/list.exp: setting listsize to -1 #7
  show listsize
  Number of source lines gdb will list by default is unlimited.
  (gdb) PASS: gdb.base/list.exp: show listsize unlimited #7
  list 1
  1       #include "list0.h"

Notice that "set listsize -1" actually failed with "integer 4294967295
out of range", but we issued a PASS anyway.

(and notice how the "listsize of 0 suppresses output" test passes bogusly too.)

This patch fixes that testsuite problem in the obvious way.

gdb/testsuite/
2013-03-28  Pedro Alves  <palves@redhat.com>

	* gdb.base/list.exp (set_listsize): Use gdb_test_no_output for
	"set listsize".
list.exp: Adjust "set listsize -1" to current test source's real line count.

The "set listsize -1" test in list.exp can't work correct anymore
nowadays, because the test's source files grew over time, and this
particular test was never updated.

This fixes it in the obvious way.

gdb/testsuite/
2013-03-28  Pedro Alves  <palves@redhat.com>

	* gdb.base/list.exp (test_listsize): Adjust test to make sure we
	list the whole file.
list.exp: Avoid hardcoding line numbers.

The previous patch actually wasn't the first time I had to update line
numbers in this file.

This avoids hard coding line numbers, hopefully making the next time a
little easier.

Tested on x86_64 Fedora 17.

gdb/testsuite/
2013-03-28  Pedro Alves  <palves@redhat.com>

	* gdb.base/list.exp (last_line): New global.
	(last_line_re): New global.
	(test_listsize, test_list_function, test_list_forward)
	(test_repeat_list_command, test_list_range)
	(test_list_filename_and_function): Use them.
	* gdb.base/list0.c: Comment the last line of the file with "last
	line".
Fix PR gdb/15294: list with unlimited listsize broken

Currently, "set listsize -1" is supposed to mean "unlimited" source
lines, but, alas, it doesn't actually work:

 (gdb) set listsize -1
 (gdb) show listsize
 Number of source lines gdb will list by default is unlimited.
 (gdb) list 1
 (gdb) list 1
 (gdb) list 1
 (gdb) set listsize 10
 (gdb) list 1
 1       /* Main function for CLI gdb.
 2          Copyright (C) 2002-2013 Free Software Foundation, Inc.
 3
 4          This file is part of GDB.
 5
 6          This program is free software; you can redistribute it and/or modify
 7          it under the terms of the GNU General Public License as published by
 8          the Free Software Foundation; either version 3 of the License, or
 9          (at your option) any later version.
 10

Before this patch:

     http://sourceware.org/ml/gdb-patches/2012-08/msg00367.html

was applied, the "set listsize" command was a var_integer command, and
"unlimited" was set with 0.  Internally, var_integer maps 0 to INT_MAX

   case var_integer:
      {
      ...
	if (val == 0 && c->var_type == var_integer)
	  val = INT_MAX;

The change in that patch to zuinteger_unlimited command, meant that -1
is left as -1 in the command's control variable (lines_to_list), and
the code in source.c isn't expecting that -- it only expects positive
numbers.

I previously suggested fixing the code and keeping the new behavior,
but I found that "set listsize 0" is currently used in the wild, and
we do have a bunch of other commands where "0" means unlimited, so I'm
thinking that changing this command alone in isolation is not a good
idea.

So I now strongly prefer reverting back the behavior in 7.6 to the
same behavior the command has had since 2006 (0==unlimited, -1=error).
Before that, set listsize -1 would be accepted as unlimited as well.

After 7.6 is out, in mainline, we can get back to reconsidering
changing this command's behavior, if there's a real need for being
able to suppress output.  For now, let's play it safe.

The "list line 1 with unlimited listsize" test in list.exp was
originally written years and years ago expecting 0 to mean "no
output", but GDB never actually worked that way, even when the tests
were written, so the tests had been xfailed then.  This patch now
adjusts the test to the new behavior, so that the test actually
passes, and the xfail is removed.

gdb/
2013-03-28  Pedro Alves  <palves@redhat.com>

	PR gdb/15294

	* source.c (_initialize_source): Change back "set listsize" to an
	integer command.

gdb/testsuite/
2013-03-28  Pedro Alves  <palves@redhat.com>

	PR gdb/15294

	* gdb.base/list.exp (set_listsize): Adjust to accept $arg == 0 to
	mean unlimited instead of $arg < 0.
	(test_listsize): Remove "listsize of 0 suppresses output" test.
	Test that "set listsize 0" ends up with an unlimited listsize.

gdb/doc/
2013-03-28  Pedro Alves  <palves@redhat.com>

	PR gdb/15294

	* gdb.texinfo (List) <set listsize>: Adjust to document that
	listsize 0 means no limit, and remove mention of -1.
	* python/python.c (finish_python_initialization): Provide suggestion
	for how to tell gdb to find its python files.
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