[PATCH] gdb: Only paginate for filtered output in fputs_maybe_filtered

[PATCH] gdb: Only paginate for filtered output in fputs_maybe_filtered

[Lancelot SIX]

A have had situation where a unfiltered output (done using
fputs_unfiltered) ended up triggering pagination.  The backtrace for this was:

    ...
    #24 0x000055839377ee4e in check_async_event_handlers () at ../../gdb/async-event.c:335
    #25 0x0000558394b67b57 in gdb_do_one_event () at ../../gdbsupport/event-loop.cc:216
    #26 0x0000558394587454 in gdb_readline_wrapper (prompt=0x7ffd907712d0 "--Type <RET> for more, q to quit, c to continue without paging--") at ../../gdb/top.c:1148
    #27 0x0000558394707270 in prompt_for_continue () at ../../gdb/utils.c:1438
    #28 0x00005583947088b3 in fputs_maybe_filtered (linebuffer=0x60c0000f4000 "   [...quite big message...]", stream=0x60300028e9d0, filter=0) at ../../gdb/utils.c:1752
    #29 0x0000558394708e57 in fputs_unfiltered (linebuffer=0x60c0000f4000 "   [...quite big message...]", stream=0x60300028e9d0) at ../../gdb/utils.c:1811
    ...

This comes from what appears to be a oversight in fputs_maybe_filtered.  This
function has a FILTER parameter which if true makes the function pause after
every screenful (i.e. triggers pagination).

The filter parameter is correctly used to guard the first place where
prompt_for_continue.  There is a second place in the function which can call
prompt_for_continue, but is currently unguarded.  I believe that this is an
oversight, this patch fixes that.

Tested on Linux-x86_64, no regression observed.

Change-Id: Iad8ffd50a87cf20077500878e2564b5a7dc81ece
---
 gdb/utils.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/gdb/utils.c b/gdb/utils.c
index dcb42138d39..505a88aa1cd 100644
--- a/gdb/utils.c
+++ b/gdb/utils.c
@@ -1744,7 +1744,8 @@ fputs_maybe_filtered (const char *linebuffer, struct ui_file *stream,
 	      /* Possible new page.  Note that
 		 PAGINATION_DISABLED_FOR_COMMAND might be set during
 		 this loop, so we must continue to check it here.  */
-	      if (lines_printed >= lines_per_page - 1
+	      if (filter
+		  && lines_printed >= lines_per_page - 1
 		  && !pagination_disabled_for_command)
 		{
 		  prompt_for_continue ();

base-commit: fb583cfc0936554a1f8d86ef2b6649bf511d6df8
-- 
2.25.1

Re: [PATCH] gdb: Only paginate for filtered output in fputs_maybe_filtered

[Tom Tromey]

>>>>> ">" == Lancelot SIX via Gdb-patches <gdb-patches@sourceware.org> writes:

>> The filter parameter is correctly used to guard the first place where
>> prompt_for_continue.  There is a second place in the function which can call
>> prompt_for_continue, but is currently unguarded.  I believe that this is an
>> oversight, this patch fixes that.

Thanks, this is ok.

It's perhaps worth noting that I believe this is also fixed by my series
to change the filter to be a more ordinary ui_file.

Tom

Re: [PATCH] gdb: Only paginate for filtered output in fputs_maybe_filtered

[Lancelot SIX]

On 17/02/2022 23:59, Tom Tromey wrote:
> [CAUTION: External Email]
> 
>>>>>> ">" == Lancelot SIX via Gdb-patches <gdb-patches@sourceware.org> writes:
> 
>>> The filter parameter is correctly used to guard the first place where
>>> prompt_for_continue.  There is a second place in the function which can call
>>> prompt_for_continue, but is currently unguarded.  I believe that this is an
>>> oversight, this patch fixes that.
> 
> Thanks, this is ok.
> 
> It's perhaps worth noting that I believe this is also fixed by my series
> to change the filter to be a more ordinary ui_file.
> 

Hi,

Thanks.  I have to admit that when I hit into that that ringed a bell 
about this series I did see.  I did not really got back to it (shame on 
me).  I'll have a look to see if your series fixes that as well, and I 
am happy not getting this in and wait for your series if you prefer / it 
simplifies your life when rebasing.

Lancelot.

> Tom

Re: [PATCH] gdb: Only paginate for filtered output in fputs_maybe_filtered

[Lancelot SIX]

> Thanks, this is ok.
> 
> Tom

Thanks,

I just pushed this.

Best,
Lancelot.