gdb: fix display of thread condition for multi-location breakpoints

This commit addresses the issue in PR gdb/30087.

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, but this is then repeated on the next line
with 'stop only in thread 1'.

In contrast, for breakpoint 2, the 'thread 1' appears randomly, in the
"What" column, though slightly offset, non of the separate locations
have the 'thread 1' information.  Additionally for breakpoint 2 we
also get a 'stop only in thread 1' line.

There's two things going on here.  First the randomly placed 'thread
1' for breakpoint 2 is due to a bug in print_one_breakpoint_location,
where we check the 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

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.

However, there's still some duplication here.  Both breakpoints 2 and
3 include a 'stop only in thread 1' line, and it feels like the
additional 'thread 1' is redundant.  In fact, there's a comment to
this very effect in the code:

  /* FIXME: This seems to be redundant and lost here; see the
     "stop only in" line a little further down.  */

So, lets fix this FIXME.  The new plan is to remove all the trailing
'thread 1' markers from the CLI output, we now get this:

  (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
  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
          stop only in thread 1

All of the above points are also true for the Ada 'task' breakpoint
condition, and the changes I've made also update how the task
information is printed, though in the case of the Ada task there was
no 'stop only in task XXX' line printed, so I've added one of those.

Obviously it can't be quite that easy.  For MI backwards compatibility
I've retained the existing code (but now only for MI like outputs),
which ensures we should generate backwards compatible output.

I've extended an Ada test to cover the new task related output, and
updated all the tests I could find that checked for the old output.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30087

Approved-By: Pedro Alves <[email protected]>

Author: T-J-Teru

gdb/breakpoint.c

@@ -6468,20 +6468,19 @@ print_one_breakpoint_location (struct breakpoint *b,
       output_thread_groups (uiout, "thread-groups", inf_nums, mi_only);
     }
 
-  if (!part_of_multiple)
+  /* In the MI output, each location of a thread or task specific
+     breakpoint includes the relevant thread or task ID.  This is done for
+     backwards compatibility reasons.
+
+     For the CLI output, the thread/task information is printed on a
+     separate line, see the 'stop only in thread' and 'stop only in task'
+     output below.  */
+  if (!header_of_multiple && uiout->is_mi_like_p ())
     {
       if (b->thread != -1)
-	{
-	  /* FIXME: This seems to be redundant and lost here; see the
-	     "stop only in" line a little further down.  */
-	  uiout->text (" thread ");
-	  uiout->field_signed ("thread", b->thread);
-	}
+	uiout->field_signed ("thread", b->thread);
       else if (b->task != 0)
-	{
-	  uiout->text (" task ");
-	  uiout->field_signed ("task", b->task);
-	}
+	uiout->field_signed ("task", b->task);
     }
 
   uiout->text ("\n");
@@ -6536,7 +6535,14 @@ print_one_breakpoint_location (struct breakpoint *b,
 	}
       uiout->text ("\n");
     }
-  
+
+  if (!part_of_multiple && b->task != 0)
+    {
+      uiout->text ("\tstop only in task ");
+      uiout->field_signed ("task", b->task);
+      uiout->text ("\n");
+    }
+
   if (!part_of_multiple)
     {
       if (b->hit_count)

gdb/testsuite/gdb.ada/tasks.exp

@@ -50,21 +50,18 @@ gdb_test "watch j task 1 task 3" "You can specify only one task\\."
 # breakpoint in the list that matched the triggered-breakpoint's
 # address, no matter which task it was specific to.
 gdb_test "break break_me task 1" "Breakpoint .* at .*"
+gdb_test "info breakpoints" "foo.adb:${decimal}\r\n\\s+stop only in task 1" \
+    "check info breakpoints for task 1 breakpoint"
 
 # Now, insert a breakpoint that should stop only if task 3 stops, and
 # extract its number.
-set bp_number -1
-set test "break break_me task 3"
-gdb_test_multiple $test $test {
-    -re "Breakpoint (.*) at .*$gdb_prompt $" {
-	set bp_number $expect_out(1,string)
-	pass $test
-    }
-}
-
+gdb_breakpoint "break_me task 3" message
+set bp_number [get_integer_valueof "\$bpnum" -1]
 if {$bp_number < 0} {
     return
 }
+gdb_test "info breakpoints" "foo.adb:${decimal}\r\n\\s+stop only in task 3" \
+    "check info breakpoints for task 3 breakpoint"
 
 # Continue to that breakpoint.  Task 2 should hit it first, and GDB
 # is expected to ignore that hit and resume the execution.  Only then

gdb/testsuite/gdb.base/save-bp.exp

@@ -79,7 +79,7 @@ gdb_test_sequence "info break" "info break" [list				\
   "\[\r\n\]+Num +Type +Disp +Enb +Address +What"				\
   "\[\r\n\]+$bp_row_start break_me at \[^\r\n\]*$srcfile:\[0-9\]+"		\
   "\[\r\n\]+$bp_row_start main at \[^\r\n\]*$srcfile:$loc_bp2"			\
-  "\[\r\n\]+$bp_row_start main at \[^\r\n\]*$srcfile:$loc_bp3 +thread 1"	\
+  "\[\r\n\]+$bp_row_start main at \[^\r\n\]*$srcfile:$loc_bp3"			\
   "\[\r\n\]+\[ \t]+stop only in thread 1"					\
   "\[\r\n\]+$bp_row_start main at \[^\r\n\]*$srcfile:$loc_bp4"			\
   "\[\r\n\]+\[ \t\]+stop only if i == 1( \\((host|target) evals\\))?"		\

gdb/testsuite/gdb.base/thread-bp-multi-loc.c

@@ -0,0 +1,44 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2022-2023 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;
+}

gdb/testsuite/gdb.base/thread-bp-multi-loc.exp

@@ -0,0 +1,67 @@
+# Copyright 2022-2023 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 -1
+}
+
+if {![runto_main]} {
+    return -1
+}
+
+delete_breakpoints
+
+gdb_breakpoint "foo thread 1"
+set bp_number [get_integer_valueof "\$bpnum" 0]
+if { $bp_number == 0 } {
+    unresolved "breakpoint not placed correctly"
+    return -1
+}
+
+set saw_header false
+set saw_cond false
+set loc_count 0
+gdb_test_multiple "info breakpoints" \
+    "check thread condition is displayed correctly" {
+    -re "\r\nNum\\s+\[^\r\n\]+\r\n" {
+	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+\[^\r\n\]+:${decimal}\r\n" {
+	incr loc_count
+	exp_continue
+    }
+
+    -re "^$gdb_prompt $" {
+	gdb_assert { $saw_header && $saw_cond && $loc_count == 3} \
+	    $gdb_test_name
+    }
+}