RE: [PATCH 3/6] gdb: fix display of thread condition for multi-location breakpoints

["Aktemur, Tankut Baris" <tankut.baris.aktemur@intel.com>]

On Monday, November 28, 2022 12:26 PM, Andrew Burgess wrote:
> If a breakpoint with multiple locations has a thread condition, then
> the 'info breakpoints' output is a little messed up, here's an example
> of the current output:
> 
>   (gdb) break foo thread 1
>   Breakpoint 2 at 0x401114: foo. (3 locations)
>   (gdb) break bar thread 1
>   Breakpoint 3 at 0x40110a: file /tmp/src/gdb/testsuite/gdb.base/thread-bp-multi-loc.c, line
> 32.
>   (gdb) info breakpoints
>   Num     Type           Disp Enb Address            What
>   2       breakpoint     keep y   <MULTIPLE>          thread 1
>           stop only in thread 1
>   2.1                         y   0x0000000000401114 in foo at
> /tmp/src/gdb/testsuite/gdb.base/thread-bp-multi-loc.c:25
>   2.2                         y   0x0000000000401146 in foo at
> /tmp/src/gdb/testsuite/gdb.base/thread-bp-multi-loc.c:25
>   2.3                         y   0x0000000000401168 in foo at
> /tmp/src/gdb/testsuite/gdb.base/thread-bp-multi-loc.c:25
>   3       breakpoint     keep y   0x000000000040110a in bar at
> /tmp/src/gdb/testsuite/gdb.base/thread-bp-multi-loc.c:32 thread 1
>           stop only in thread 1
> 
> Notice that, at the end of the location for breakpoint 3, the 'thread
> 1' condition is printed.
> 
> In contrast, for breakpoint 2, the 'thread 1' appears randomly, in the
> "What" column, though slightly offset.
> 
> I believe this is a bug in GDB, in the function
> print_one_breakpoint_location, due to checking the local variable
> part_of_multiple, instead of header_of_multiple.
> 
> If I fix this oversight, then the output is now:
> 
>   (gdb) break foo thread 1
>   Breakpoint 2 at 0x401114: foo. (3 locations)
>   (gdb) break bar thread 1
>   Breakpoint 3 at 0x40110a: file /tmp/src/gdb/testsuite/gdb.base/thread-bp-multi-loc.c, line
> 32.
>   (gdb) info breakpoints
>   Num     Type           Disp Enb Address            What
>   2       breakpoint     keep y   <MULTIPLE>
>           stop only in thread 1
>   2.1                         y   0x0000000000401114 in foo at
> /tmp/src/gdb/testsuite/gdb.base/thread-bp-multi-loc.c:25 thread 1
>   2.2                         y   0x0000000000401146 in foo at
> /tmp/src/gdb/testsuite/gdb.base/thread-bp-multi-loc.c:25 thread 1
>   2.3                         y   0x0000000000401168 in foo at
> /tmp/src/gdb/testsuite/gdb.base/thread-bp-multi-loc.c:25 thread 1
>   3       breakpoint     keep y   0x000000000040110a in bar at
> /tmp/src/gdb/testsuite/gdb.base/thread-bp-multi-loc.c:32 thread 1
>           stop only in thread 1

We already state the condition in "stop only in thread 1".
Do we need to repeat it also as part of the location?

> The 'thread 1' condition is now displayed at the end of each location,
> which makes the output the same for single location breakpoints and
> multi-location breakpoints.
> ---
>  gdb/breakpoint.c                              |  2 +-
>  gdb/testsuite/gdb.base/thread-bp-multi-loc.c  | 44 ++++++++++
>  .../gdb.base/thread-bp-multi-loc.exp          | 88 +++++++++++++++++++
>  3 files changed, 133 insertions(+), 1 deletion(-)
>  create mode 100644 gdb/testsuite/gdb.base/thread-bp-multi-loc.c
>  create mode 100644 gdb/testsuite/gdb.base/thread-bp-multi-loc.exp
> 
> diff --git a/gdb/breakpoint.c b/gdb/breakpoint.c
> index f0276a963c0..2ec8ca364b6 100644
> --- a/gdb/breakpoint.c
> +++ b/gdb/breakpoint.c
> @@ -6467,7 +6467,7 @@ print_one_breakpoint_location (struct breakpoint *b,
>        output_thread_groups (uiout, "thread-groups", inf_nums, mi_only);
>      }
> 
> -  if (!part_of_multiple)
> +  if (!header_of_multiple)
>      {
>        if (b->thread != -1)
>  	{
> diff --git a/gdb/testsuite/gdb.base/thread-bp-multi-loc.c b/gdb/testsuite/gdb.base/thread-
> bp-multi-loc.c
> new file mode 100644
> index 00000000000..cab009c39ec
> --- /dev/null
> +++ b/gdb/testsuite/gdb.base/thread-bp-multi-loc.c
> @@ -0,0 +1,44 @@
> +/* This testcase is part of GDB, the GNU debugger.
> +
> +   Copyright 2022 Free Software Foundation, Inc.
> +
> +   This program is free software; you can redistribute it and/or modify
> +   it under the terms of the GNU General Public License as published by
> +   the Free Software Foundation; either version 3 of the License, or
> +   (at your option) any later version.
> +
> +   This program is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> +   GNU General Public License for more details.
> +
> +   You should have received a copy of the GNU General Public License
> +   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
> +
> +volatile int global_var = 0;
> +
> +__attribute__((__always_inline__)) static inline void
> +foo (void)
> +{
> +  int i;
> +
> +  for (i = 0; i < 10; ++i)
> +    global_var = i;
> +}
> +
> +static void
> +bar (void)
> +{
> +  global_var = 0;
> +  foo ();
> +}
> +
> +int
> +main (void)
> +{
> +  global_var = 0;
> +  foo ();
> +  bar ();
> +  foo ();
> +  return 0;
> +}
> diff --git a/gdb/testsuite/gdb.base/thread-bp-multi-loc.exp b/gdb/testsuite/gdb.base/thread-
> bp-multi-loc.exp
> new file mode 100644
> index 00000000000..9abff5866d9
> --- /dev/null
> +++ b/gdb/testsuite/gdb.base/thread-bp-multi-loc.exp
> @@ -0,0 +1,88 @@
> +# Copyright 2022 Free Software Foundation, Inc.
> +
> +# This program is free software; you can redistribute it and/or modify
> +# it under the terms of the GNU General Public License as published by
> +# the Free Software Foundation; either version 3 of the License, or
> +# (at your option) any later version.
> +#
> +# This program is distributed in the hope that it will be useful,
> +# but WITHOUT ANY WARRANTY; without even the implied warranty of
> +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> +# GNU General Public License for more details.
> +#
> +# You should have received a copy of the GNU General Public License
> +# along with this program.  If not, see <http://www.gnu.org/licenses/>.
> +
> +# Create a multi-location breakpoint with a thread condition, then check the
> +# output of 'info breakpoints' to ensure that the thread condition is
> +# displayed correctly.
> +
> +standard_testfile
> +
> +if { [prepare_for_testing "failed to prepare" $testfile $srcfile] } {
> +    return
> +}
> +
> +if ![runto_main] then {

Maybe use {} here, too, for consistency.

> +    return

The testsuite is unfortunately highly inconsistent about what to do here.
There is "return 0", "return 1", "return -1", and "return".
If we cannot run to the main function, "return -1" seems a better choice
to me.  What do you think?

> +}
> +
> +gdb_test_no_output "with confirm off -- delete breakpoints"

Why not use delete_breakpoints?

> +
> +set bp_number ""
> +gdb_test_multiple "break foo thread 1" "" {
> +    -re "^break foo thread 1\r\n" {
> +	exp_continue
> +    }
> +    -re "^Breakpoint ($decimal) at $hex: foo\[^\r\n\]+3 locations\[^\r\n\]+\r\n" {
> +	set bp_number $expect_out(1,string)
> +	exp_continue
> +    }
> +    -re "^$gdb_prompt $" {
> +	gdb_assert { ![string eq $bp_number ""] }
> +    }
> +}
> +
> +if { $bp_number == "" } {
> +    unresolved "breakpoint not placed correctly"
> +    return
> +}

An alternative could be to use "gdb_breakpoint" followed by

set bp_number [get_integer_valueof "\$bpnum" 0]


> +
> +set saw_header false
> +set saw_cond false
> +set loc_count 0
> +gdb_test_multiple "info breakpoints" "" {
> +    -re "^info breakpoints\r\n" {
> +	exp_continue
> +    }
> +
> +    -re "^Num\\s+\[^\r\n\]+\r\n" {

If we remove "^" at the beginning, we can also get rid of the 
first regexp above for a bit shorter code.

Thanks
-Baris

> +	exp_continue
> +    }
> +
> +    -re "^$bp_number\\s+breakpoint\\s+keep\\s+y\\s+<MULTIPLE>\\s*\r\n" {
> +	set saw_header true
> +	exp_continue
> +    }
> +
> +    -re "^\\s+stop only in thread 1\r\n" {
> +	set saw_cond true
> +	exp_continue
> +    }
> +
> +    -re "^$bp_number\\.\[123\]\\s+\[^\r\n\]+ thread 1\r\n" {
> +	incr loc_count
> +	exp_continue
> +    }
> +
> +    -re "^$gdb_prompt $" {
> +	with_test_prefix $gdb_test_name {
> +	    gdb_assert { $saw_header } \
> +		"saw header line"
> +	    gdb_assert { $saw_cond } \
> +		"saw b/p condition line"
> +	    gdb_assert { $loc_count == 3 } \
> +		"saw all three locations"
> +	}
> +    }
> +}
> --
> 2.25.4

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