binutils-gdb/gdb/testsuite/gdb.base/double-prompt-target-event-error.exp
Pedro Alves c3f814a143 Fix paginate-*.exp races
Jan pointed out in
<https://sourceware.org/ml/gdb-patches/2014-07/msg00553.html> that
these testcases have racy results:

  gdb.base/double-prompt-target-event-error.exp
  gdb.base/paginate-after-ctrl-c-running.exp
  gdb.base/paginate-bg-execution.exp
  gdb.base/paginate-execution-startup.exp
  gdb.base/paginate-inferior-exit.exp

This is easily reproducible with "read1" from:

  [reproducer for races of expect incomplete reads]
  http://sourceware.org/bugzilla/show_bug.cgi?id=12649

The '-notransfer -re "<return>" { exp_continue }' trick in the current
tests doesn't actually work.

The issue that led to the -notransfer trick was that

  "---Type <return> to continue, or q <return> to quit---"

has two "<return>"s.  If one wants gdb_test_multiple to not hit the
built-in "<return>" match that results in FAIL, one has to expect the
pagination prompt in chunks, first up to the first "<return>", then
again, up to the second.  Something around these lines:

  gdb_test_multiple "" $test {
      -re "<return>" {
	  exp_continue
      }
      -re "to quit ---" {
	  pass $test
      }
  }

The intent was for -notransfer+exp_continue to make expect fetch more
input, and rerun the matches against the now potentially fuller
buffer, and then eventually the -re that includes the full pagination
prompt regex would match instead (because it's listed higher up, it
would match first).  But, once that "<return>" -notransfer -re
matches, it keeps re-matching forever.  It seems like with
exp_continue, expect immediately retries matching, instead of first
reading in more data into the buffer, if available.

Fix this like I should have done in the first place.  There's actually
no good reason for gdb_test_multiple to only match "<return>".  We can
make gdb_test_multiple expect the whole pagination prompt text
instead, which is store in the 'pagination_prompt' global (similar to
'gdb_prompt').  Then a gdb_test_multiple caller that doesn't want the
default match to trigger, because it wants to see one pagination
prompt, does simply:

  gdb_test_multiple "" $test {
      -re "$pagination_prompt$" {
	  pass $test
      }
  }

which is just like when we don't want the default $gdb_prompt match
within gdb_test_multiple to trigger, like:

  gdb_test_multiple "" $test {
      -re "$gdb_prompt $" {
	  pass $test
      }
  }

Tested on x86_64 Fedora 20.  In addition, I've let the racy tests run
all in parallel in a loop for 30 minutes, and they never failed.

gdb/testsuite/
2014-07-25  Pedro Alves  <palves@redhat.com>

	* gdb.base/double-prompt-target-event-error.exp
	(cancel_pagination_in_target_event): Remove '-notransfer <return>'
	match.
	(cancel_pagination_in_target_event): Rework double prompt
	detection.
	* gdb.base/paginate-after-ctrl-c-running.exp
	(test_ctrlc_while_target_running_paginates): Remove '-notransfer
	<return>' match.
	* gdb.base/paginate-bg-execution.exp
	(test_bg_execution_pagination_return)
	(test_bg_execution_pagination_cancel): Remove '-notransfer
	<return>' matches.
	* gdb.base/paginate-execution-startup.exp
	(test_fg_execution_pagination_return)
	(test_fg_execution_pagination_cancel): Remove '-notransfer
	<return>' matches.
	* gdb.base/paginate-inferior-exit.exp
	(test_paginate_inferior_exited): Remove '-notransfer <return>'
	match.
	* lib/gdb-utils.exp (string_to_regexp): Move here from lib/gdb.exp.
	* lib/gdb.exp (pagination_prompt): Run text through
	string_to_regexp.
	(gdb_test_multiple): Match $pagination_prompt instead of
	"<return>".
	(string_to_regexp): Move to lib/gdb-utils.exp.
2014-07-25 10:07:38 +01:00

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# Copyright (C) 2014 Free Software Foundation, Inc.
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
standard_testfile
if {[prepare_for_testing "failed to prepare" $testfile $srcfile debug] == -1} {
return -1
}
# Test throwing an error while GDB is handling a target event. We use
# a ctrl-c/quit in a pagination prompt to emulate an error. COMMAND
# is either "continue" or "wrapcont". The latter is a continue issued
# from a user-defined command. That exercises the case of the
# interpreter forced sync, which was the case that originally had a
# bug.
proc cancel_pagination_in_target_event { command } {
global binfile srcfile
global gdb_prompt pagination_prompt
set testline [gdb_get_line_number "after sleep"]
with_test_prefix "ctrlc target event: $command" {
clean_restart $binfile
if ![runto_main] then {
fail "Can't run to main"
return 0
}
gdb_test "b $srcfile:$testline" \
"Breakpoint .*$srcfile, line $testline.*" \
"set breakpoint"
gdb_test_no_output "set height 2"
if { $command == "wrapcont" } {
gdb_test_multiple "define wrapcont" "define user command: wrapcont" {
-re "Type commands for definition of \"wrapcont\".\r\nEnd with a line saying just \"end\".\r\n>$" {
# Note that "Continuing." is ommitted when
# "continue" is issued from a user-defined
# command. Issue it ourselves.
gdb_test "echo Continuing\.\ncontinue\nend" "" \
"define user command: wrapcont"
}
}
}
# Wait for pagination prompt after the "Continuing" line,
# indicating the program was running and then stopped.
set saw_continuing 0
set test "continue to pagination"
gdb_test_multiple "$command" $test {
-re "$pagination_prompt$" {
if {$saw_continuing} {
pass $test
} else {
send_gdb "\n"
exp_continue
}
}
-re "Continuing" {
set saw_continuing 1
exp_continue
}
}
# We're now stopped in a pagination query while handling a
# target event (printing where the program stopped). Quitting
# the pagination should result in only one prompt being
# output.
send_gdb "\003p 1\n"
# Note gdb_test_multiple has a default match for the prompt,
# which issues a FAIL. Consume the first prompt.
set test "first prompt"
gdb_test_multiple "" $test {
-re "$gdb_prompt" {
pass "first prompt"
}
}
# We should only see one prompt more, and it should be
# preceeded by print's output.
set test "no double prompt"
gdb_test_multiple "" $test {
-re "$gdb_prompt.*$gdb_prompt $" {
# The bug is present, and expect managed to read
# enough characters into the buffer to fill it with
# both prompts.
fail $test
}
-re " = 1\r\n$gdb_prompt $" {
pass $test
}
}
# In case the board file wants to send further commands.
gdb_test_no_output "set height unlimited"
}
}
foreach variant { "continue" "wrapcont" } {
cancel_pagination_in_target_event $variant
}