gdb: don't set breakpoint::pspace in create_breakpoint

I spotted this code within create_breakpoint:

  if ((type_wanted != bp_breakpoint
      && type_wanted != bp_hardware_breakpoint) || thread != -1)
   b->pspace = current_program_space;

this code is only executed when creating a pending breakpoint, and
sets the breakpoint::pspace member variable.

The above code gained the 'thread != -1' clause with this commit:

  commit cc72b2a2da6d6372cbdb1d14639a5fce84e1a325
  Date:   Fri Dec 23 17:06:16 2011 +0000

              Introduce gdb.FinishBreakpoint in Python

While the type_wanted checks were added with this commit:

  commit f8eba3c61629b3c03ac1f33853eab4d8507adb9c
  Date:   Tue Dec 6 18:54:43 2011 +0000

      the "ambiguous linespec" series

Before this breakpoint::pspace was set unconditionally.

If we look at how breakpoint::pspace is used today, some breakpoint
types specifically set this field, either in their constructors, or in
a wrapper function that calls the constructor.  So, the watchpoint
type and its sub-class set this variable, as does the catchpoint type,
and all it's sub-classes.

However, code_breakpoint doesn't specifically set this field within
its constructor, though some sub-classes of
code_breakpoint (ada_catchpoint, exception_catchpoint,
internal_breakpoint, and momentary_breakpoint) do set this field.

When I examine all the places that breakpoint::pspace is used, I
believe that in every place where it is expected that this field is
set, the breakpoint type will be one that specifically sets this
field.

Next, I observe two problems with the existing code.

First, the above code is only hit for pending breakpoints, there's no
equivalent code for non-pending breakpoints.  This opens up the
possibility of GDB entering non-consistent states; if a breakpoint is
first created pending and then later gets a location, the pspace field
will be set, while if the breakpoint is immediately non-pending, then
the pspace field will never be set.

Second, if we look at how breakpoint::pspace is used in the function
breakpoint_program_space_exit, we see that when a program space is
removed, any breakpoint with breakpoint::pspace set to the removed
program space, will be deleted.  This makes sense, but does mean we
need to ensure breakpoint::pspace is only set for breakpoints that
apply to a single program space.

So, if I create a pending dprintf breakpoint (type bp_dprintf) then
the breakpoint::pspace variable will be set even though the dprintf is
not really tied to that one program space.  As a result, when the
matching program space is removed the dprintf is incorrectly removed.

Also, if I create a thread specific breakpoint, then, thanks to the
'thread != -1' clause the wrong program space will be stored in
breakpoint::pspace (the current program space is always used, which
might not be the program space that corresponds to the selected
thread), as a result, the thread specific breakpoint will be deleted
when the matching program space is removed.

If we look at commit cc72b2a2da6d which added the 'thread != -1'
clause, we can see this change was entirely redundant, the
breakpoint::pspace is also set in bpfinishpy_init after
create_breakpoint has been called.  As such, I think we can safely
drop the 'thread != -1' clause.

For the other problems, I'm proposing to be pretty aggressive - I'd
like to drop the breakpoint::pspace assignment completely from
create_breakpoint.  Having looked at how this variable is used, I
believe that it is already set elsewhere in all the cases that it is
needed.  Maybe this code was needed at one time, but I can't see how
it's needed any more.

There's tests to expose the issues I've spotted with this code, and
there's no regressions in testing.

4 files changed, 259 insertions, 6 deletions

diff --git a/gdb/breakpoint.c b/gdb/breakpoint.c
index 9e30dbc..8860ec4 100644
--- a/gdb/breakpoint.c
+++ b/gdb/breakpoint.c
@@ -9242,9 +9242,6 @@ create_breakpoint (struct gdbarch *gdbarch,
       b->disposition = tempflag ? disp_del : disp_donttouch;
       b->condition_not_parsed = 1;
       b->enable_state = enabled ? bp_enabled : bp_disabled;
-      if ((type_wanted != bp_breakpoint
-	   && type_wanted != bp_hardware_breakpoint) || thread != -1)
-	b->pspace = current_program_space;
 
       if (b->type == bp_dprintf)
 	update_dprintf_command_list (b.get ());
diff --git a/gdb/breakpoint.h b/gdb/breakpoint.h
index 0641653..77b754f 100644
--- a/gdb/breakpoint.h
+++ b/gdb/breakpoint.h
@@ -828,9 +828,21 @@ struct breakpoint : public intrusive_list_node<breakpoint>
      equals this.  */
   struct frame_id frame_id = null_frame_id;
 
-  /* The program space used to set the breakpoint.  This is only set
-     for breakpoints which are specific to a program space; for
-     non-thread-specific ordinary breakpoints this is NULL.  */
+  /* The program space used to set the breakpoint.  This is only set for
+     breakpoints that are not type bp_breakpoint or bp_hardware_breakpoint.
+     For thread or inferior specific breakpoints, the breakpoints are
+     managed via the thread and inferior member variables.  */
+
+  /* If not nullptr then this is the program space for which this
+     breakpoint was created.  All watchpoint and catchpoint sub-types set
+     this field, but not all of the code_breakpoint sub-types do;
+     generally, user created breakpoint types don't set this field, though
+     things might be more consistent if they did.
+
+     When this variable is nullptr then a breakpoint might be associated
+     with multiple program spaces, though you need to check the thread,
+     inferior and task variables to see if a breakpoint was created for a
+     specific thread, inferior, or Ada task respectively.  */
   program_space *pspace = NULL;
 
   /* The location specification we used to set the breakpoint.  */
diff --git a/gdb/testsuite/gdb.multi/pending-bp-del-inferior.c b/gdb/testsuite/gdb.multi/pending-bp-del-inferior.c
new file mode 100644
index 0000000..1d03000
--- /dev/null
+++ b/gdb/testsuite/gdb.multi/pending-bp-del-inferior.c
@@ -0,0 +1,28 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 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/>.  */
+
+int
+foo (void)
+{
+  return 0;
+}
+
+int
+main (void)
+{
+  return foo ();
+}
diff --git a/gdb/testsuite/gdb.multi/pending-bp-del-inferior.exp b/gdb/testsuite/gdb.multi/pending-bp-del-inferior.exp
new file mode 100644
index 0000000..5fcd1ef
--- /dev/null
+++ b/gdb/testsuite/gdb.multi/pending-bp-del-inferior.exp
@@ -0,0 +1,216 @@
+# Copyright 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/>.
+
+# Setup two inferiors.  Select one inferior and create a pending
+# thread specific breakpoint in the other inferior.
+#
+# Delete the selected inferior (the one for which the thread specific
+# breakpoint doesn't apply), and check that the breakpoint still exists.
+#
+# Repeat this process, but this time, create an inferior specific
+# breakpoint.
+
+# The plain remote target can't do multiple inferiors.
+require !use_gdb_stub
+
+standard_testfile
+
+if {[prepare_for_testing "failed to prepare" $testfile $srcfile]} {
+    return -1
+}
+
+# Setup for the tests.  Create two inferiors, both running the global
+# BINFILE, and proceed to main in both inferiors.  Delete all
+# breakpoints, and check that we do have two threads.
+#
+# Return true after a successful setup, otherwise, return false.
+proc test_setup {} {
+    clean_restart $::binfile
+
+    if {![runto_main]} {
+	return 0
+    }
+
+    gdb_test "add-inferior -exec ${::binfile}" "Added inferior 2.*" \
+	"add inferior 2"
+    gdb_test "inferior 2" "Switching to inferior 2 .*" \
+	"select inferior 2"
+
+    if {![runto_main]} {
+	return 0
+    }
+
+    delete_breakpoints
+
+    gdb_test "info threads" \
+	[multi_line \
+	     "  Id\\s+Target Id\\s+Frame\\s*" \
+	     "  1\\.1\\s+\[^\r\n\]+" \
+	     "\\* 2\\.1\\s+\[^\r\n\]+"] \
+	"check we have the expected threads"
+
+    return 1
+}
+
+# Assuming inferior 2 is already selected, kill the current inferior
+# (inferior 2), select inferior 1, and then remove inferior 2.
+proc kill_and_remove_inferior_2 {} {
+    gdb_test "kill" "" "kill inferior 2" \
+	"Kill the program being debugged.*y or n. $" "y"
+
+    gdb_test "inferior 1" "Switching to inferior 1 .*" \
+	"select inferior 1"
+
+    gdb_test_no_output "remove-inferiors 2"
+}
+
+# Setup two inferiors, then create a breakpoint.  If BP_PENDING is
+# true then the breakpoint will be pending, otherwise, the breakpoint
+# will be non-pending.
+#
+# BP_TYPE is either 'thread' or 'inferior', and indicates if the
+# created breakpoint should be thread or inferior specific.
+#
+# The breakpoint is created while inferior 2 is selected, and the
+# thread/inferior restriction always identifies inferior 1.
+#
+# Then inferior 2 is killed and removed.
+#
+# Finally, check that the breakpoint still exists and correctly refers
+# to inferior 1.
+proc do_bp_test { bp_type bp_pending } {
+    if {![test_setup]} {
+	return
+    }
+
+    if { $bp_pending } {
+	set bp_func "bar"
+    } else {
+	set bp_func "foo"
+    }
+
+    if { $bp_type eq "thread" } {
+	set bp_restriction "thread 1.1"
+    } else {
+	set bp_restriction "inferior 1"
+    }
+
+    gdb_breakpoint "$bp_func $bp_restriction" allow-pending
+    set bp_number [get_integer_valueof "\$bpnum" "INVALID" \
+		       "get b/p number for previous breakpoint"]
+
+    if { $bp_restriction eq "thread 1.1" } {
+	set bp_after_restriction "thread 1"
+    } else {
+	set bp_after_restriction $bp_restriction
+    }
+
+    if { $bp_pending } {
+	set bp_pattern_before \
+	    [multi_line \
+		 "$bp_number\\s+breakpoint\\s+keep\\s+y\\s+<PENDING>\\s+${bp_func}" \
+		 "\\s+stop only in [string_to_regexp $bp_restriction]"]
+	set bp_pattern_after \
+	    [multi_line \
+		 "$bp_number\\s+breakpoint\\s+keep\\s+y\\s+<PENDING>\\s+${bp_func}" \
+		 "\\s+stop only in [string_to_regexp $bp_after_restriction]"]
+    } else {
+	set bp_pattern_before \
+	    [multi_line \
+		 "$bp_number\\s+breakpoint\\s+keep\\s+y\\s+<MULTIPLE>\\s*" \
+		 "\\s+stop only in [string_to_regexp $bp_restriction]" \
+		 "$bp_number\\.1\\s+y\\s+$::hex in $bp_func at \[^\r\n\]+ inf 1" \
+		 "$bp_number\\.2\\s+y\\s+$::hex in $bp_func at \[^\r\n\]+ inf 2"]
+
+	set bp_pattern_after \
+	    [multi_line \
+		 "$bp_number\\s+breakpoint\\s+keep\\s+y\\s+$::hex in $bp_func at \[^\r\n\]+" \
+		 "\\s+stop only in [string_to_regexp $bp_after_restriction]"]
+    }
+
+    gdb_test "info breakpoints" $bp_pattern_before \
+	"info breakpoints before inferior removal"
+
+    kill_and_remove_inferior_2
+
+    gdb_test "info breakpoints" $bp_pattern_after \
+	"info breakpoints after inferior removal"
+}
+
+# Setup two inferiors, then create a dprintf.  If BP_PENDING is
+# true then the dprintf will be pending, otherwise, the dprintf
+# will be non-pending.
+#
+# The dprintf is created while inferior 2 is selected.  Then inferior
+# 2 is killed and removed.
+#
+# Finally, check that the dprintf still exists.
+proc do_dprintf_test { bp_pending } {
+    if {![test_setup]} {
+	return
+    }
+
+    if { $bp_pending } {
+	set bp_func "bar"
+
+	gdb_test "dprintf $bp_func,\"in $bp_func\"" ".*" \
+	    "create dprintf breakpoint" \
+	    "Make dprintf pending on future shared library load\\? \\(y or .n.\\) $" "y"
+    } else {
+	set bp_func "foo"
+
+	gdb_test "dprintf $bp_func,\"in $bp_func\"" ".*" \
+	    "create dprintf breakpoint"
+    }
+
+    set bp_number [get_integer_valueof "\$bpnum" "INVALID" \
+		       "get b/p number for previous breakpoint"]
+
+    if { $bp_pending } {
+	set bp_pattern_before \
+	    [multi_line \
+		 "$bp_number\\s+dprintf\\s+keep\\s+y\\s+<PENDING>\\s+${bp_func}" \
+		 "\\s+printf \"in $bp_func\""]
+	set bp_pattern_after $bp_pattern_before
+    } else {
+	set bp_pattern_before \
+	    [multi_line \
+		 "$bp_number\\s+dprintf\\s+keep\\s+y\\s+<MULTIPLE>\\s*" \
+		 "\\s+printf \"in $bp_func\"" \
+		 "$bp_number\\.1\\s+y\\s+$::hex in $bp_func at \[^\r\n\]+ inf 1" \
+		 "$bp_number\\.2\\s+y\\s+$::hex in $bp_func at \[^\r\n\]+ inf 2"]
+
+	set bp_pattern_after \
+	    [multi_line \
+		 "$bp_number\\s+dprintf\\s+keep\\s+y\\s+$::hex in $bp_func at \[^\r\n\]+" \
+		 "\\s+printf \"in $bp_func\""]
+    }
+
+    gdb_test "info breakpoints" $bp_pattern_before \
+	"info breakpoints before inferior removal"
+
+    kill_and_remove_inferior_2
+
+    gdb_test "info breakpoints" $bp_pattern_after \
+	"info breakpoints after inferior removal"
+}
+
+foreach_with_prefix bp_pending { true false } {
+    foreach_with_prefix bp_type { thread inferior } {
+	do_bp_test $bp_type $bp_pending
+    }
+
+    do_dprintf_test $bp_pending
+}