[PATCH] gdb/python: Handle unnamed frames in caller-matching functions

[PATCH] gdb/python: Handle unnamed frames in caller-matching functions

[Dmitry Ivanov (A)]

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gdb.Frame.name() can return None when GDB cannot determine a frame's
function name.   and  currently
pass that value directly to Python's regular expression functions,
causing a TypeError.

Treat unnamed frames as non-matches.  For None, keep
walking older frames after encountering an unnamed frame.

Add regression tests for both convenience functions.
---

This is my first GDB contribution.

I used ChatGPT to help investigate the issue and draft an initial
version of the patch (it's fairly simple but still worth mentioning).
I reviewed, simplified, and tested the final change myself.

Tested with:

  make -C gdb check RUNTESTFLAGS='gdb.python/py-caller-is.exp'

gdb/python/lib/gdb/function/caller_is.py  |  6 ++++--
gdb/testsuite/gdb.python/py-caller-is.exp | 20 ++++++++++++++++++++
2 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/gdb/python/lib/gdb/function/caller_is.py b/gdb/python/lib/gdb/function/caller_is.py
index bca09590811..a2a5798b914 100644
--- a/gdb/python/lib/gdb/function/caller_is.py
+++ b/gdb/python/lib/gdb/function/caller_is.py
@@ -80,7 +80,8 @@ class CallerMatches(gdb.Function):
             if frame is None:
                 return False
             nframes = nframes - 1
-        return re.match(name.string(), frame.name()) is not None
+        frame_name = frame.name()
+        return frame_name is not None and re.match(name.string(), frame_name) is not None


 class AnyCallerIs(gdb.Function):
@@ -143,7 +144,8 @@ class AnyCallerMatches(gdb.Function):
         frame = gdb.selected_frame()
         name_re = re.compile(name.string())
         while nframes >= 0:
-            if name_re.match(frame.name()) is not None:
+            frame_name = frame.name()
+            if frame_name is not None and name_re.match(frame_name) is not None:
                 return True
             frame = frame.older()
             if frame is None:
diff --git a/gdb/testsuite/gdb.python/py-caller-is.exp b/gdb/testsuite/gdb.python/py-caller-is.exp
index d9b826cb6a2..74ee2ae645a 100644
--- a/gdb/testsuite/gdb.python/py-caller-is.exp
+++ b/gdb/testsuite/gdb.python/py-caller-is.exp
@@ -70,3 +70,23 @@ proc test_all_caller_is_fns { } {
}

 test_all_caller_is_fns
+
+# Prepend an unnamed frame to the current stack without depending on
+# missing symbols in the host's runtime libraries.
+gdb_test_multiline "define unnamed frame helper" \
+    "python" "" \
+    "from unittest.mock import Mock, patch" "" \
+    "def check_unnamed_frame(expr):" "" \
+    "    frame = Mock()" "" \
+    "    frame.name.return_value = None" "" \
+    "    frame.older.return_value = gdb.selected_frame()" "" \
+    "    with patch.object(gdb, 'selected_frame', return_value=frame):" "" \
+    "        print(int(gdb.parse_and_eval(expr)))" "" \
+    "end" ""
+
+gdb_test {python check_unnamed_frame('$_caller_matches(".*", 0)')} \
+    "0" "caller_matches with unnamed frame"
+gdb_test {python check_unnamed_frame('$_any_caller_matches(".*", 0)')} \
+    "0" "any_caller_matches with unnamed frame"
+gdb_test {python check_unnamed_frame('$_any_caller_matches("^bottom_func$", 1)')} \
+    "1" "any_caller_matches skips unnamed frame"
--
2.34.1


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Re: [PATCH] gdb/python: Handle unnamed frames in caller-matching functions

[Tom Tromey]

>>>>> Dmitry Ivanov (A) <dmitry.ivanov1@huawei.com> writes:

> This is my first GDB contribution.

Hi.  However you sent this, the mail got pretty mangled somewhere.
There are a lot of extra newlines.  So it can't be applied as-is.

> +        frame_name = frame.name()
> +        return frame_name is not None and re.match(name.string(), frame_name) is not None

I wonder if instead the None case should be turned into an empty string
here, so a user of $_caller_matches could match against "^$" to detect
nameless frames.

I think this would be as easy as

    frame_name = frame.name() or ""

In this case perhaps the documentation could be updated a bit as well.

> +# Prepend an unnamed frame to the current stack without depending on
> +# missing symbols in the host's runtime libraries.

Cool technique.

Tom