gdb/testsuite/gdb.base/pc-not-saved.exp

# Copyright 2024 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/>.

# Test how GDB handles a frame in which the previous-pc value is not
# available.  Specifically, check that the backtrace correctly reports
# why the backtrace is truncated, and ensure that 'display' directives
# still work when 'stepi'-ing through the frame.
#
# We do this by registering a Python unwinder which doesn't provide
# any previous register values.

require allow_python_tests

standard_testfile

if { [prepare_for_testing "failed to prepare" ${testfile} ${srcfile}] } {
    return
}

set remote_python_file \
    [gdb_remote_download host "${srcdir}/${subdir}/${testfile}.py"]

if { ![runto "break_bt_here"] } {
    return
}

# Figuring out the correct frame-id from a Python unwinder is hard.
# We need to know the function's start address (not too hard), and the
# stack address on entry to the function, which is much harder to
# figure out in a cross-target way.
#
# So instead we run without any Python unwinder in place and use
# 'maint print frame-id' to record the frame-id.  We then restart GDB,
# load the Python unwinder, and tell it to use the frame-id we
# recorded here.
set pc unknown
set cfa unknown
gdb_test_multiple "maintenance print frame-id" "store break_bt_here frame-id" {
    -re -wrap "frame-id for frame #0: \\{stack=($hex),code=($hex),\[^\}\]+\\}" {
	set cfa $expect_out(1,string)
	set pc $expect_out(1,string)
    }
}
gdb_assert { ![string equal $cfa unknown] } \
    "check we read the frame's CFA"

gdb_assert { ![string equal $pc unknown] } \
    "check we read the frame's PC"

# Restart and load the Python unwinder script.
clean_restart $binfile
gdb_test_no_output "source ${remote_python_file}" "load python file"

# Tell the Python unwinder to use the frame-id we cached above.
gdb_test_no_output "python set_break_bt_here_frame_id($pc, $cfa)"

# Run up to the function which the unwinder will claim.
if { ![runto "break_bt_here"] } {
    return
}

# Print the backtrace.  Check that the reason for stopping the
# backtrace is that the previous $pc is not available.
gdb_test "bt" \
    [multi_line \
	 "^#0  break_bt_here \\(\\) at \[^\r\n\]+" \
	 "Backtrace stopped: frame did not save the PC"] \
    "backtrace from break_bt_here function"

# Ensure we can stepi.
gdb_test "stepi" \
    "(:?$hex\\s+)?$decimal\\s+\[^\r\n\]+" \
    "stepi without a display in place"

# Setup a 'display' directive.
gdb_test "display/i \$pc" \
    [multi_line \
	 "^1: x/i \\\$pc" \
	 "=> $hex <break_bt_here(:?\\+$decimal)?>:\\s+\[^\r\n\]+"]

# Step again, check the 'display' directive is shown.
gdb_test "stepi" \
    [multi_line \
	 "(:?$hex\\s+)?$decimal\\s+\[^\r\n\]+" \
	 "1: x/i \\\$pc" \
	 "=> $hex <break_bt_here(:?\\+$decimal)?>:\\s+\[^\r\n\]+"] \
    "stepi with a display in place"

# Continue to a function that is called from within break_bt_here.
# The Python unwinder will then be claiming frame #1.
gdb_breakpoint other_func
gdb_continue_to_breakpoint "continue to other_func"

# Print the backtrace and check that the reason for stopping the
# backtrace is that the previous $pc is not available.
gdb_test "bt" \
    [multi_line \
	 "#0  other_func \\(\\) at \[^\r\n\]+" \
	 "#1  (:?$hex in )?break_bt_here \\(\\) at \[^\r\n\]+" \
	 "Backtrace stopped: frame did not save the PC"] \
    "backtrace from other_func function"