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 an error is thrown while handling a target event (within
fetch_inferior_event), and, the interpreter is not async (but the
target is), then GDB prints the prompt twice.
One way to see that in action is throw a QUIT while in a pagination
prompt issued from within fetch_inferior_event (or one of its
callees). E.g. from the test:
---Type <return> to continue, or q <return> to quit---
^CQuit
(gdb) (gdb) p 1
^^^^^^^^^^^
$1 = 1
(gdb)
The issue is that inferior_event_handler swallows errors and notifies
the observers (the interpreters) about the command error, even if the
interpreter is forced sync while we're handling a nested event loop
(for execute_command). The observers print a prompt, and then when we
get back to the top event loop, we print another (in
start_event_loop).
I see no reason the error should be swallowed here. Just cancel the
execution related bits and let the error propagate to the top level
(start_event_loop), which re-enables stdin and notifies observers.
gdb/
2014-07-14 Pedro Alves <palves@redhat.com>
* inf-loop.c (inferior_event_handler): Use TRY_CATCH instead of
catch_errors. Don't re-enable stdin or notify observers where,
and rethrow error.
(fetch_inferior_event_wrapper): Delete.
gdb/testsuite/
2014-07-14 Pedro Alves <palves@redhat.com>
* gdb.base/double-prompt-target-event-error.c: New file.
* gdb.base/double-prompt-target-event-error.exp: New file.
Luis Machado
Joel Brobecker
Sandra Loosemore
Pedro Alves