Re: [PATCH v4] [PR python/29603] Disable out-of-scope watchpoints

[Simon Marchi <simark@simark.ca>]

> diff --git a/gdb/testsuite/gdb.python/py-watchpoint.exp b/gdb/testsuite/gdb.python/py-watchpoint.exp
> new file mode 100644
> index 0000000000..5504736629
> --- /dev/null
> +++ b/gdb/testsuite/gdb.python/py-watchpoint.exp
> @@ -0,0 +1,54 @@
> +# Copyright (C) 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/>.
> +
> +# Check that Watchpoints are deleted after use.
> +
> +load_lib gdb-python.exp
> +
> +standard_testfile
> +
> +if {[prepare_for_testing "failed to prepare" $testfile $srcfile]} {
> +    return -1
> +}
> +
> +# Skip all tests if Python scripting is not enabled.
> +if { [skip_python_tests] } { continue }
This needs to be updated to:

  require allow_python_tests

> +
> +if ![runto_main] then {
> +    return 0
> +}
> +
> +# For remote host testing
> +set pyfile [gdb_remote_download host ${srcdir}/${subdir}/${testfile}.py]
> +
> +gdb_test_no_output "set can-use-hw-watchpoints 0" "don't use hardware watchpoints"
> +gdb_test "break 24" ".*" "set breakpoint before loop"

Avoid using hardcoded line numbers.  Either break on a symbol (function)
name, or put a comment in the source code and use gdb_get_line_number.

> diff --git a/gdb/testsuite/gdb.python/py-watchpoint.py b/gdb/testsuite/gdb.python/py-watchpoint.py
> new file mode 100644
> index 0000000000..c5fae00e93
> --- /dev/null
> +++ b/gdb/testsuite/gdb.python/py-watchpoint.py
> @@ -0,0 +1,30 @@
> +# Copyright (C) 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/>.
> +
> +
> +class MyBreakpoint(gdb.Breakpoint):
> +    def __init__(self, *args, **kwargs):
> +        gdb.Breakpoint.__init__(self, *args, **kwargs)
> +        self.n = 0

I think it would be a bit more straightforward to read if you passed the
arguments to the base class directly:

    def __init__(self):
      super().__init__("i", gdb.BP_WATCHPOINT)
      self.n = 0

I think we can use the super() notation, now that we only support Python
3?

> +
> +    def stop(self):
> +        self.n += 1
> +        print("Watchpoint Hit:", self.n, flush=True)
> +        return False
> +
> +
> +MyBreakpoint("i", gdb.BP_WATCHPOINT)
> +
> +print("Python script imported")

I tried your test with the native-gdbserver and
native-extended-gdbserver boards, and for some reason it doesn't work.
You can try with:

    $ make check TESTS="gdb.python/py-watchpoint.exp" RUNTESTFLAGS="--target_board=native-extended-gdbserver"

In gdb.log:

    ...
    Python script imported
    (gdb) PASS: gdb.python/py-watchpoint.exp: import python scripts
    python print(len(gdb.breakpoints()))
    2
    (gdb) PASS: gdb.python/py-watchpoint.exp: check modified BP count
    gdb_expect_list pattern: /Watchpoint Hit: 1/
    continue
    Continuing.
    Watchpoint Hit: 1
    gdb_expect_list pattern: /Watchpoint Hit: 2/
    FAIL: gdb.python/py-watchpoint.exp: run until program stops (pattern 2) (timeout)

I didn't dig to understand why, but we would need to fix that before
merging.

Simon