[PATCH v11 10/10] gdb: Filter trampoline frames in backtrace when using Python frame-filters.
Abdul Basit Ijaz <[email protected]> Mon, 3 Aug 2026 21:34:49 +0200
| Newsgroups | gmane.comp.gdb.patches |
|---|---|
| Message-ID | <[email protected]> |
In case of the Python frame-filters, this change filters trampoline functions
when the option 'skip-trampoline-functions' is set to 'on'. GDB recently
added the option to hide frames that are marked by the compiler with
"DW_AT_trampoline", see commit 'Skip trampoline frames for the backtrace
command'. This implements the same functionality when python frame filters
are in use.
In this example the IFX compiler emits "DW_AT_trampoline" tag for the 'first'
and 'second' trampoline functions like following:
function second (x, y) result(z)
integer, intent(in) :: x, y
integer :: z
z = x * y ! breakpt-framefilter
end function second
function first (num1, num2) result(total)
integer, intent(in) :: num1, num2
integer :: total
total = second (num1 + 4, num2 * 3) ! first-breakpt
total = total + 30
end function first
Related Dwarf:
0x0000013f: DW_TAG_subprogram
DW_AT_low_pc (0x0000000000404350)
DW_AT_high_pc (0x000000000040435f)
DW_AT_frame_base (DW_OP_reg6 RBP)
DW_AT_linkage_name ("second_.t74p.t75p")
DW_AT_name ("second_.t74p.t75p")
DW_AT_trampoline ("second_")
0x0000015a: DW_TAG_subprogram
DW_AT_low_pc (0x00000000004044a0)
DW_AT_high_pc (0x00000000004044af)
DW_AT_frame_base (DW_OP_reg6 RBP)
DW_AT_linkage_name ("first_.t104p.t105p")
DW_AT_name ("first_.t104p.t105p")
DW_AT_trampoline ("first_")
Once frame filters are enabled the backtrace command output before this
change looks like:
'''
(gdb) info frame-filter
global frame-filters:
Priority Enabled Name
100 Yes TestTrampolineFrameFilter
(gdb) backtrace 3
\#0 second (x=20, y=9) at test.f90:4
\#1 0x0000000000405209 in second_.t74p.t75p () at test.f90:12
\#2 0x00000000004051e3 in first (num1=16, num2=3) at test.f90:10
(gdb) backtrace -3
\#2 0x00000000004051e3 in first (num1=16, num2=3) at test.f90:10
\#3 0x0000000000405309 in first_.t95p.t96p () at test.f90:21
\#4 0x0000000000405234 in func_trampoline () at test.f90:17
'''
After this change:
'''
(gdb) info frame-filter
global frame-filters:
Priority Enabled Name
100 Yes TestTrampolineFrameFilter
(gdb) backtrace 3
\#0 second (x=20, y=9) at test.f90:4
\#2 0x00000000004051e3 in first (num1=16, num2=3) at test.f90:10
\#4 0x0000000000405234 in func_trampoline () at test.f90:17
(gdb) backtrace -3
\#2 0x00000000004051e3 in first (num1=16, num2=3) at test.f90:10
\#4 0x0000000000405234 in func_trampoline () at test.f90:17
'''
New test gdb.python/py-framefilter-trampoline.exp is added to test this
change.
---
gdb/python/py-frame.c | 11 +++
.../gdb.python/py-framefilter-trampoline.exp | 77 +++++++++++++++++++
.../gdb.python/py-framefilter-trampoline.py | 31 ++++++++
3 files changed, 119 insertions(+)
create mode 100644 gdb/testsuite/gdb.python/py-framefilter-trampoline.exp
create mode 100644 gdb/testsuite/gdb.python/py-framefilter-trampoline.py
diff --git a/gdb/python/py-frame.c b/gdb/python/py-frame.c
index afa89f0d112..098b37230e1 100644
--- a/gdb/python/py-frame.c
+++ b/gdb/python/py-frame.c
@@ -59,6 +59,17 @@ frame_object_to_frame_info (PyObject *obj)
if (frame == NULL)
return NULL;
+ if (skip_trampoline_functions)
+ {
+ for (int i = 0; (SAFE_TRAMPOLINE_CHAIN (i, frame)
+ && in_trampoline_frame (frame)); ++i)
+ {
+ frame = get_prev_frame (frame);
+ if (frame == nullptr)
+ return nullptr;
+ }
+ }
+
return frame;
}
diff --git a/gdb/testsuite/gdb.python/py-framefilter-trampoline.exp b/gdb/testsuite/gdb.python/py-framefilter-trampoline.exp
new file mode 100644
index 00000000000..23fd22164ef
--- /dev/null
+++ b/gdb/testsuite/gdb.python/py-framefilter-trampoline.exp
@@ -0,0 +1,77 @@
+# Copyright (C) 2026 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. It tests skipping of trampolines
+# in the backtrace command in case Python-based frame-filters are enabled.
+
+load_lib gdb-python.exp
+
+require allow_python_tests allow_fortran_tests
+
+if {![test_compiler_info {ifx-*} f90]} {
+ untested "This test is only applicable for IFX, which emits the\
+ trampoline DIE in Dwarf."
+ return
+}
+
+load_lib fortran.exp
+
+set testfile py-framefilter-trampoline
+set srcfile "${srcdir}/gdb.fortran/func-trampoline.f90"
+set binfile [standard_output_file $testfile]
+
+if {[build_executable $testfile.exp $testfile $srcfile {debug f90}] == -1} {
+ return
+}
+
+# Start with a fresh gdb.
+gdb_exit
+gdb_start
+
+gdb_test "info frame-filter" \
+ "No frame filters\\." \
+ "info frame filter before loading filters"
+
+gdb_reinitialize_dir $srcdir/$subdir
+gdb_load ${binfile}
+
+if {![runto_main]} {
+ return
+}
+gdb_test_no_output "set python print-stack full" \
+ "set python print-stack to full"
+
+# Load frame-filters
+set remote_python_file [gdb_remote_download host \
+ ${srcdir}/${subdir}/${testfile}.py]
+gdb_test_no_output "source ${remote_python_file}" "load python file"
+
+set inner_loc [gdb_get_line_number "second-breakpt"]
+set middle_loc [gdb_get_line_number "first-breakpt"]
+set outer_loc [gdb_get_line_number "main-outer-loc"]
+set fill "\[^\r\n\]*"
+
+set inner_desc "second \\(x=20, y=9\\) at ${fill}$srcfile:$inner_loc"
+set middle_desc "first \\(num1=16, num2=3\\) at ${fill}$srcfile:$middle_loc"
+set outer_desc ".* at .*$srcfile:$outer_loc"
+
+# Set breakpoint inside the innermost function 'second'.
+gdb_breakpoint "$srcfile:$inner_loc"
+gdb_continue_to_breakpoint "innermost-body" ".*$srcfile:$inner_loc.*"
+
+# Test with frame filter.
+gdb_test "bt" [multi_line \
+ "#$decimal.* $middle_desc" \
+ "#$decimal.* $outer_desc.*"]
diff --git a/gdb/testsuite/gdb.python/py-framefilter-trampoline.py b/gdb/testsuite/gdb.python/py-framefilter-trampoline.py
new file mode 100644
index 00000000000..0cdaf7bb4de
--- /dev/null
+++ b/gdb/testsuite/gdb.python/py-framefilter-trampoline.py
@@ -0,0 +1,31 @@
+# Copyright (C) 2026 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. It tests if trampolines are
+# skipped when Python-based frame-filters are enabled.
+
+import gdb
+
+class TestTrampolineFrameFilter():
+ def __init__(self):
+ self.name = "TestTrampolineFrameFilter"
+ self.priority = 100
+ self.enabled = True
+ gdb.frame_filters[self.name] = self
+
+ def filter(self, frame_iter):
+ return frame_iter
+
+TestTrampolineFrameFilter()
--
2.34.1
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