gdb/testsuite/gdb.threads/vfork-multi-inferior.exp

# Copyright 2020-2022 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/>.

# Test handling a vfork while another inferior is running.  The bug that
# prompted writing this test case was in the Linux native target.  The target
# assumed that the vfork-done event it received was for the current inferior
# (an invalid assumption, the current inferior is the one randomly selected by
# do_target_wait (at the time of writing).  This caused the target to drop the
# vfork-done event, because it was seen as unneeded and to restart the thread
# as if nothing happened.  This however resulted in the thread running with
# breakpoints not inserted.
#
# To catch the bug, this test verifies that we can hit a breakpoint after a
# vfork call, while a second inferior runs in the background.

if [use_gdb_stub] {
    unsupported "test uses multiple inferiors"
    return
}

standard_testfile .c -sleep.c

set srcfile_sleep $srcfile2
set binfile_sleep ${binfile}-sleep

# The reproducibility of the bug depends on which inferior randomly selects in
# do_target_wait when consuming the vfork-done event.  Since GDB doesn't call
# srand(), we are likely to always see the same sequence of inferior selected by
# do_target_wait, which can hide the bug if you are not "lucky".  To work
# around that, call vfork and hit the breakpoint in a loop, it makes it
# somewhat likely that the wrong inferior will be selected eventually.
set nr_loops 20

# Compile the main program that calls vfork and hits a breakpoint.
set opts [list debug additional_flags=-DNR_LOOPS=$nr_loops]
if  { [gdb_compile "${srcdir}/${subdir}/${srcfile}" "${binfile}" executable \
	$opts] != "" } {
    untested "failed to compile"
    return -1
}

# Compile the secondary program, which just sleeps.
if  { [gdb_compile "${srcdir}/${subdir}/${srcfile_sleep}" "${binfile_sleep}" executable \
	{debug}] != "" } {
    untested "failed to compile"
    return -1
}

# We exercise two methods of getting a second inferior to execute while the
# first one vforks.  METHOD can be:
#
#   - non-stop: start GDB with non-stop on and run the second inferior in
#               background.
#   - schedule-multiple: set "schedule-multiple on", this will make "continue"
#                        resume both inferiors.
proc do_test {method} {
    save_vars { ::GDBFLAGS } {
	if { $method == "non-stop" } {
	    append ::GDBFLAGS " -ex \"set non-stop on\""
	}
	clean_restart
    }

    # Start the second inferior in background.
    gdb_test "add-inferior" "Added inferior 2.*"
    gdb_test "inferior 2" "Switching to inferior 2 .*"
    gdb_file_cmd ${::binfile_sleep}
    if { $method == "non-stop" } {
	gdb_test "run &" "Starting program: .*" "run inferior 2"
    } else {
	gdb_test "start" "Temporary breakpoint $::decimal, main .*" \
		"start inferior 2"
    }

    # Start the first inferior.
    gdb_test "inferior 1" "Switching to inferior 1 .*"
    gdb_file_cmd ${::binfile}
    gdb_test "break should_break_here" "Breakpoint $::decimal at .*"
    gdb_test "start" "Thread 1.1 .* hit Temporary breakpoint.*" \
	"start inferior 1"

    # Only enable schedule-multiple this late, because of:
    # https://sourceware.org/bugzilla/show_bug.cgi?id=28777
    if { $method == "schedule-multiple" } {
	gdb_test_no_output "set schedule-multiple on"
    }


    # Continue over vfork and until the breakpoint.  The number of loops here
    # matches the number of loops in the program.  So if a breakpoint is missed
    # at some point, a "continue" will wrongfully continue until the end of the
    # program, which will fail the test.
    for {set i 0} {$i < $::nr_loops} {incr i} {
	with_test_prefix "i=$i" {
	    gdb_test "continue" \
		"Thread 1.1 .* hit Breakpoint $::decimal, should_break_here.*"
	}
    }
}

foreach_with_prefix method {schedule-multiple non-stop} {
    do_test $method
}