Re: [PATCH v2 3/3] gdb: introduce scoped debug prints

[tdevries <tdevries@suse.de>]

On 2021-01-05 18:02, Simon Marchi wrote:
> On 2021-01-05 10:33 a.m., Simon Marchi via Gdb-patches wrote:
>> Thanks for reporting.  The test passes here 90% of the time, but when 
>> I
>> run it in a loop it eventually fails like the others I fixed.
>> 
>> I'd rather add a -prompt flag to gdb_test_sequence, what do you think?

Yeah, that's not a bad idea.

The only bit that concerns me is that there's already a -prompt switch 
for gdb_test_multiple, which does not add on the terminating '$', while 
this version does.

It's probably a good idea to have the -prompt switch to behave the same 
in both cases.

Thanks,
- Tom


>> I'll start working on that and give it a try.
> 
> Here's what I propose:
> 
> From fac85012df91bc9b70e2d1d8df12de1dab2ab44c Mon Sep 17 00:00:00 2001
> From: Simon Marchi <simon.marchi@polymtl.ca>
> Date: Tue, 5 Jan 2021 11:02:07 -0500
> Subject: [PATCH] gdb/testsuite: fix race in
>  gdb.threads/signal-while-stepping-over-bp-other-thread.exp
> 
> Commit 3ec3145c5dd6 ("gdb: introduce scoped debug prints") updated some
> tests using "set debug infrun" to handle the fact that a debug print is
> now shown after the prompt, after an inferior stop.  The same issue
> happens in gdb.threads/signal-while-stepping-over-bp-other-thread.exp.
> If I run it in a loop, it eventually fails like these other tests.
> 
> The problem is that the testsuite expects to see $gdb_prompt followed 
> by
> the end of the buffer.  It happens that expect reads $gdb_prompt and 
> the
> debug print at the same time, in which case the regexp never matches 
> and
> we get a timeout.
> 
> The fix is the same as was done in 3ec3145c5dd6, make the testsuite
> believe that the prompt is the standard GDB prompt followed by that
> debug print.
> 
> Since that test uses gdb_test_sequence, and the expected prompt is in
> gdb_test_sequence, add a -prompt switch to gdb_test_sequence to 
> override
> the prompt used for that call.
> 
> gdb/testsuite/ChangeLog:
> 
> 	* lib/gdb.exp (gdb_test_sequence): Accept -prompt switch.
> 	* gdb.threads/signal-while-stepping-over-bp-other-thread.exp:
> 	Pass prompt containing debug print to gdb_test_sequence.
> 
> Change-Id: I33161c53ddab45cdfeadfd50b964f8dc3caa9729
> ---
>  ...al-while-stepping-over-bp-other-thread.exp |  2 +-
>  gdb/testsuite/lib/gdb.exp                     | 23 +++++++++++++++++--
>  2 files changed, 22 insertions(+), 3 deletions(-)
> 
> diff --git
> a/gdb/testsuite/gdb.threads/signal-while-stepping-over-bp-other-thread.exp
> b/gdb/testsuite/gdb.threads/signal-while-stepping-over-bp-other-thread.exp
> index fe8425319779..cc8b3200fbc2 100644
> --- 
> a/gdb/testsuite/gdb.threads/signal-while-stepping-over-bp-other-thread.exp
> +++ 
> b/gdb/testsuite/gdb.threads/signal-while-stepping-over-bp-other-thread.exp
> @@ -102,7 +102,7 @@ gdb_test "set scheduler-locking off"
>  gdb_test "set debug infrun 1"
> 
>  set test "step"
> -gdb_test_sequence $test $test {
> +gdb_test_sequence $test $test -prompt "$gdb_prompt \\\[infrun\\\]
> fetch_inferior_event: exit\r\n"  {
>      "need to step-over"
>      "resume_1: step=1,"
>      "signal arrived while stepping over breakpoint"
> diff --git a/gdb/testsuite/lib/gdb.exp b/gdb/testsuite/lib/gdb.exp
> index 3f61da8adf12..f3880ecf56bb 100644
> --- a/gdb/testsuite/lib/gdb.exp
> +++ b/gdb/testsuite/lib/gdb.exp
> @@ -1401,6 +1401,9 @@ proc gdb_test_no_output { args } {
>  # EXPECTED_OUTPUT_LIST is a list of regexps of expected output, which 
> are
>  # processed in order, and all must be present in the output.
>  #
> +# The -prompt switch can be used to override the prompt expected at 
> the end of
> +# the output sequence.
> +#
>  # It is unnecessary to specify ".*" at the beginning or end of any 
> regexp,
>  # there is an implicit ".*" between each element of 
> EXPECTED_OUTPUT_LIST.
>  # There is also an implicit ".*" between the last regexp and the gdb 
> prompt.
> @@ -1413,16 +1416,32 @@ proc gdb_test_no_output { args } {
>  #    0 if the test passes,
>  #   -1 if there was an internal error.
> 
> -proc gdb_test_sequence { command test_name expected_output_list } {
> +proc gdb_test_sequence { args } {
>      global gdb_prompt
> +
> +    parse_args {{prompt ""}}
> +
> +    if { $prompt == "" } {
> +	set prompt "$gdb_prompt "
> +    }
> +
> +    if { [llength $args] != 3 } {
> +	error "Unexpected # of arguments, expecting: COMMAND TEST_NAME
> EXPECTED_OUTPUT_LIST"
> +    }
> +
> +    lassign $args command test_name expected_output_list
> +
>      if { $test_name == "" } {
>  	set test_name $command
>      }
> +
>      lappend expected_output_list ""; # implicit ".*" before gdb prompt
> +
>      if { $command != "" } {
>  	send_gdb "$command\n"
>      }
> -    return [gdb_expect_list $test_name "$gdb_prompt $" 
> $expected_output_list]
> +
> +    return [gdb_expect_list $test_name "${prompt}$" 
> $expected_output_list]
>  }
> 
>  \f