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.
If pagination occurs as result of output sent as response to a target
event while the target is executing in the background, subsequent
input aborts readline/gdb:
$ gdb program
...
(gdb) continue&
Continuing.
(gdb)
---Type <return> to continue, or q <return> to quit---
*return*
---Type <return> to continue, or q <return> to quit---
Breakpoint 2, after_sleep () at paginate-bg-execution.c:21
---Type <return> to continue, or q <return> to quit---
21 return; /* after sleep */
p 1
readline: readline_callback_read_char() called with no handler!
*abort/SIGABRT*
$
gdb_readline_wrapper_line removes the handler after a line is
processed. Usually, we'll end up re-displaying the prompt, and that
reinstalls the handler. But if the output is coming out of handling
a stop event, we don't re-display the prompt, and nothing restores the
handler. So the next input wakes up the event loop and calls into
readline, which aborts.
We should do better with the prompt handling while the target is
running (I think we should coordinate with readline, and
hide/redisplay it around output), but that's a more invasive change
better done post 7.8, so this patch is conservative and just
reinstalls the handler as soon as we're out of the readline line
callback.
gdb/
2014-07-14 Pedro Alves <palves@redhat.com>
PR gdb/17072
* top.c (gdb_readline_wrapper_line): Tweak comment.
(gdb_readline_wrapper_cleanup): If readline is enabled, reinstall
the input handler callback.
gdb/testsuite/
2014-07-14 Pedro Alves <palves@redhat.com>
PR gdb/17072
* gdb.base/paginate-bg-execution.c: New file.
* gdb.base/paginate-bg-execution.exp: New file.
