[PATCH 04/30] Don't set immediate_quit in prompt_for_continue

Pedro Alves
2016-03-18T19:25:35Z

immediate_quit used to be necessary back when prompt_for_continue used
blocking fread, but nowadays it uses gdb_readline_wrapper, which is
implemented in terms of a nested event loop, which already knows how
to react to SIGINT:

#0 throw_it (reason=RETURN_QUIT, error=GDB_NO_ERROR, fmt=0x9d6d7e "Quit", ap=0x7fffffffcb88)
at /home/pedro/gdb/mygit/cxx-convertion/src/gdb/common/common-exceptions.c:324
#1 0x00000000007bab5d in throw_vquit (fmt=0x9d6d7e "Quit", ap=0x7fffffffcb88) at /home/pedro/gdb/mygit/cxx-convertion/src/gdb/common/common-exceptions.c:366
#2 0x00000000007bac9f in throw_quit (fmt=0x9d6d7e "Quit") at /home/pedro/gdb/mygit/cxx-convertion/src/gdb/common/common-exceptions.c:385
#3 0x0000000000773a2d in quit () at /home/pedro/gdb/mygit/cxx-convertion/src/gdb/utils.c:1039
#4 0x000000000065d81b in async_request_quit (arg=0x0) at /home/pedro/gdb/mygit/cxx-convertion/src/gdb/event-top.c:893
#5 0x000000000065c27b in invoke_async_signal_handlers () at /home/pedro/gdb/mygit/cxx-convertion/src/gdb/event-loop.c:949
#6 0x000000000065aeef in gdb_do_one_event () at /home/pedro/gdb/mygit/cxx-convertion/src/gdb/event-loop.c:280
#7 0x0000000000770838 in gdb_readline_wrapper (prompt=0x7fffffffcd40 "---Type <return> to continue, or q <return> to quit---")
at /home/pedro/gdb/mygit/cxx-convertion/src/gdb/top.c:873

The need for the QUIT in stdin_event_handler is then exposed by the
gdb.base/double-prompt-target-event-error.exp test, which has:

# 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"

Without that change we'd get:

Continuing.
---Type <return> to continue, or q <return> to quit---PASS: gdb.base/double-prompt-target-event-error.exp: ctrlc target event: continue: continue to pagination
^CpQuit
(gdb) 1
Undefined command: "1". Try "help".
(gdb) PASS: gdb.base/double-prompt-target-event-error.exp: ctrlc target event: continue: first prompt
ERROR: Undefined command "".
UNRESOLVED: gdb.base/double-prompt-target-event-error.exp: ctrlc target event: continue: no double prompt

Vs:

Continuing.
---Type <return> to continue, or q <return> to quit---PASS: gdb.base/double-prompt-target-event-error.exp: ctrlc target event: continue: continue to pagination
^CQuit
(gdb) p 1
$1 = 1
(gdb) PASS: gdb.base/double-prompt-target-event-error.exp: ctrlc target event: continue: first prompt
PASS: gdb.base/double-prompt-target-event-error.exp: ctrlc target event: continue: no double prompt

gdb/ChangeLog:
yyyy-mm-dd Pedro Alves <palves@redhat.com>

* event-top.c (stdin_event_handler): Call QUIT;
(prompt_for_continue): Don't run with immediate_quit set.
---
gdb/event-top.c | 8 ++++++++
gdb/utils.c | 4 ----
2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/gdb/event-top.c b/gdb/event-top.c
index eb4f0b9..769485f 100644
--- a/gdb/event-top.c
+++ b/gdb/event-top.c
@@ -403,6 +403,14 @@ stdin_event_handler (int error, gdb_client_data client_data)
}
else
{
+ /* This makes sure a ^C immediately followed by further input is
+ always processed in that order. E.g,. with input like "^Cprint
+ 1\n", the SIGINT handler runs, marks the async signal handler,
+ and then select/poll may return with stdin ready, instead of
+ -1/EINTR. The gdb.base/double-prompt-target-event-error.exp
+ test exercises this. */
+ QUIT;
+
do
{
call_stdin_event_handler_again_p = 0;
diff --git a/gdb/utils.c b/gdb/utils.c
index 97e5133..a909b38 100644
--- a/gdb/utils.c
+++ b/gdb/utils.c
@@ -1836,9 +1836,6 @@ prompt_for_continue (void)
beyond the end of the screen. */
reinitialize_more_filter ();

- immediate_quit++;
- QUIT;
-
/* We'll need to handle input. */
target_terminal_ours ();

@@ -1866,7 +1863,6 @@ prompt_for_continue (void)
throw_quit ("Quit");
xfree (ignore);
}
- immediate_quit--;

/* Now we have to do this again, so that GDB will know that it doesn't
need to save the ---Type <return>--- line at the top of the screen. */
--
2.5.0