[gdb/testsuite] Add gdb.python/py-commands-breakpoint.exp

A recent discussion about what commands are allowed during
gdb.Breakpoint.stop, made me wonder if there would be less restrictions if
we'd do those commands as part of a breakpoint command list instead.

Attribute gdb.Breakpoint.commands is a string with gdb commands, so I
tried implementing a new class PyCommandsBreakpoint, derived from
gdb.Breakpoint, that supports a py_commands method.

My original idea was to forbid setting PyCommandsBreakpoint.commands, and do:
...
    def py_commands(self):
        print("VAR: %d" % self.var)
        self.var += 1
	gdb.execute("continue")
...
but as it turns out 'gdb.execute("continue")' does not behave the same way as
continue.  I've filed PR python/32454 about this.

So the unsatisfactory solution is to first execute
PyCommandsBreakpoint.py_commands:
...
    def py_commands(self):
        print("VAR: %d" % self.var)
        self.var += 1
...
and then:
...
        self.commands = "continue"
...

I was hoping for a better outcome, but having done the work of writing this, I
suppose it has use as a test-case, perhaps also as an example of how to work
around PR python/32454.

Tested on x86_64-linux.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=32454

1 files changed, 59 insertions, 0 deletions

diff --git a/gdb/testsuite/gdb.python/py-commands-breakpoint.py b/gdb/testsuite/gdb.python/py-commands-breakpoint.py
new file mode 100644
index 0000000..dbe7676
--- /dev/null
+++ b/gdb/testsuite/gdb.python/py-commands-breakpoint.py
@@ -0,0 +1,59 @@
+# Copyright (C) 2025 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/>.
+
+# This file is part of the GDB testsuite.
+
+import gdb
+
+
+class PyCommandsBreakpoint(gdb.Breakpoint):
+    bp_dict = dict()
+
+    def __init__(self, *args, **kwargs):
+        gdb.Breakpoint.__init__(self, *args, **kwargs)
+        PyCommandsBreakpoint.bp_dict[self.number] = self
+        self.commands = ""
+
+    @staticmethod
+    def run_py_commands(num):
+        bp = PyCommandsBreakpoint.bp_dict[num]
+        if hasattr(bp, "py_commands"):
+            bp.py_commands()
+
+    def __setattr__(self, name, value):
+        if name == "commands":
+            l = ["python PyCommandsBreakpoint.run_py_commands(%d)" % self.number]
+            if value != "":
+                l.append(value)
+            value = "\n".join(l)
+
+        super().__setattr__(name, value)
+
+
+class TestBreakpoint(PyCommandsBreakpoint):
+    def __init__(self):
+        PyCommandsBreakpoint.__init__(self, spec="test")
+        self.var = 1
+        self.commands = "continue"
+        self.silent = True
+
+    def stop(self):
+        if self.var == 3:
+            self.commands = ""
+        return True
+
+    def py_commands(self):
+        print("VAR: %d" % self.var)
+        self.var += 1