[gdb] Handle vfork in thread with follow-fork-mode child
When debugging any of the testcases added by this commit, which do a vfork in a thread with "set follow-fork-mode child" + "set detach-on-fork on", we run into this assertion: ... src/gdb/nat/x86-linux-dregs.c:146: internal-error: \ void x86_linux_update_debug_registers(lwp_info*): \ Assertion `lwp_is_stopped (lwp)' failed. ... The assert is caused by the following: the vfork-child exit or exec event is handled by handle_vfork_child_exec_or_exit, which calls target_detach to detach from the vfork parent. During target_detach we call linux_nat_target::detach, which: #1 - stops all the threads #2 - waits for all the threads to be stopped #3 - detaches all the threads However, during the second step we run into this code in stop_wait_callback: ... /* If this is a vfork parent, bail out, it is not going to report any SIGSTOP until the vfork is done with. */ if (inf->vfork_child != NULL) return 0; ... and we don't wait for the threads to be stopped, which results in this assert in x86_linux_update_debug_registers triggering during the third step: ... gdb_assert (lwp_is_stopped (lwp)); ... The fix is to reset the vfork parent's vfork_child field before calling target_detach in handle_vfork_child_exec_or_exit. There's already similar code for the other paths handled by handle_vfork_child_exec_or_exit, so this commit refactors the code a bit so that all paths share the same code. The new tests cover both a vfork child exiting, and a vfork child execing, since both cases would trigger the assertion. The new testcases also exercise following the vfork children with "set detach-on-fork off", since it doesn't seem to be tested anywhere. Tested on x86_64-linux, using native and native-gdbserver. gdb/ChangeLog: 2019-04-18 Tom de Vries <tdevries@suse.de> Pedro Alves <palves@redhat.com> PR gdb/24454 * infrun.c (handle_vfork_child_exec_or_exit): Reset vfork parent's vfork_child field before calling target_detach. gdb/testsuite/ChangeLog: 2019-04-18 Tom de Vries <tdevries@suse.de> Pedro Alves <palves@redhat.com> PR gdb/24454 * gdb.threads/vfork-follow-child-exec.c: New file. * gdb.threads/vfork-follow-child-exec.exp: New file. * gdb.threads/vfork-follow-child-exit.c: New file. * gdb.threads/vfork-follow-child-exit.exp: New file.
This commit is contained in:
Tom de Vries
Pedro Alves
parent
5d5b0bd35f
commit
b73715df01
31
gdb/infrun.c
31
gdb/infrun.c
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@ -915,10 +915,14 @@ handle_vfork_child_exec_or_exit (int exec)
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int resume_parent = -1;
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/* This exec or exit marks the end of the shared memory region
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between the parent and the child. If the user wanted to
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detach from the parent, now is the time. */
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between the parent and the child. Break the bonds. */
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inferior *vfork_parent = inf->vfork_parent;
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inf->vfork_parent->vfork_child = NULL;
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inf->vfork_parent = NULL;
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if (inf->vfork_parent->pending_detach)
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/* If the user wanted to detach from the parent, now is the
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time. */
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if (vfork_parent->pending_detach)
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{
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struct thread_info *tp;
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struct program_space *pspace;
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@ -926,7 +930,7 @@ handle_vfork_child_exec_or_exit (int exec)
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/* follow-fork child, detach-on-fork on. */
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inf->vfork_parent->pending_detach = 0;
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vfork_parent->pending_detach = 0;
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gdb::optional<scoped_restore_exited_inferior>
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maybe_restore_inferior;
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@ -941,7 +945,7 @@ handle_vfork_child_exec_or_exit (int exec)
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maybe_restore_thread.emplace ();
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/* We're letting loose of the parent. */
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tp = any_live_thread_of_inferior (inf->vfork_parent);
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tp = any_live_thread_of_inferior (vfork_parent);
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switch_to_thread (tp);
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/* We're about to detach from the parent, which implicitly
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@ -964,7 +968,7 @@ handle_vfork_child_exec_or_exit (int exec)
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if (print_inferior_events)
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{
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std::string pidstr
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= target_pid_to_str (ptid_t (inf->vfork_parent->pid));
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= target_pid_to_str (ptid_t (vfork_parent->pid));
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target_terminal::ours_for_output ();
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@ -982,7 +986,7 @@ handle_vfork_child_exec_or_exit (int exec)
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}
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}
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target_detach (inf->vfork_parent, 0);
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target_detach (vfork_parent, 0);
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/* Put it back. */
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inf->pspace = pspace;
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@ -997,10 +1001,7 @@ handle_vfork_child_exec_or_exit (int exec)
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inf->removable = 1;
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set_current_program_space (inf->pspace);
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resume_parent = inf->vfork_parent->pid;
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/* Break the bonds. */
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inf->vfork_parent->vfork_child = NULL;
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resume_parent = vfork_parent->pid;
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}
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else
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{
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@ -1030,17 +1031,13 @@ handle_vfork_child_exec_or_exit (int exec)
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set_current_program_space (pspace);
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inf->removable = 1;
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inf->symfile_flags = SYMFILE_NO_READ;
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clone_program_space (pspace, inf->vfork_parent->pspace);
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clone_program_space (pspace, vfork_parent->pspace);
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inf->pspace = pspace;
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inf->aspace = pspace->aspace;
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resume_parent = inf->vfork_parent->pid;
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/* Break the bonds. */
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inf->vfork_parent->vfork_child = NULL;
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resume_parent = vfork_parent->pid;
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}
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inf->vfork_parent = NULL;
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gdb_assert (current_program_space == inf->pspace);
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if (non_stop && resume_parent != -1)
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@ -1,3 +1,12 @@
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2019-04-18 Tom de Vries <tdevries@suse.de>
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Pedro Alves <palves@redhat.com>
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PR gdb/24454
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* gdb.threads/vfork-follow-child-exec.c: New file.
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* gdb.threads/vfork-follow-child-exec.exp: New file.
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* gdb.threads/vfork-follow-child-exit.c: New file.
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* gdb.threads/vfork-follow-child-exit.exp: New file.
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2019-04-15 Leszek Swirski <leszeks@google.com>
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* gdb.arch/amd64-eval.cc: New file.
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@ -0,0 +1,66 @@
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/* This testcase is part of GDB, the GNU debugger.
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Copyright 2019 Free Software Foundation, Inc.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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#include <stdio.h>
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#include <unistd.h>
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#include <pthread.h>
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#include <string.h>
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#include <stdlib.h>
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static char *program_name;
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static void *
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f (void *arg)
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{
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int res = vfork ();
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if (res == -1)
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{
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perror ("vfork");
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return NULL;
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}
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else if (res == 0)
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{
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/* Child. */
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execl (program_name, program_name, "1", NULL);
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perror ("exec");
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abort ();
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}
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else
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{
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/* Parent. */
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return NULL;
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}
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}
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int
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main (int argc, char **argv)
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{
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pthread_t tid;
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if (argc > 1)
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{
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/* Getting here via execl. */
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return 0;
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}
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program_name = argv[0];
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pthread_create (&tid, NULL, f, NULL);
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pthread_join (tid, NULL);
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return 0;
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}
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@ -0,0 +1,64 @@
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# Copyright (C) 2019 Free Software Foundation, Inc.
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 3 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program. If not, see <http://www.gnu.org/licenses/>. */
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# Test following a vfork child that execs, when the vfork parent is a
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# threaded program, and it's a non-main thread that vforks.
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standard_testfile
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if {[build_executable "failed to prepare" $testfile $srcfile {debug pthreads}]} {
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return -1
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}
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# DETACH indicates whether "set detach-on-fork" is enabled. It is
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# either "on" or "off".
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proc test_vfork {detach} {
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global binfile
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clean_restart $binfile
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if ![runto_main] then {
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fail "can't run to main"
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return 0
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}
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delete_breakpoints
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gdb_test_no_output "set follow-fork-mode child"
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gdb_test_no_output "set detach-on-fork $detach"
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if {$detach == "off"} {
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gdb_test "continue" \
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[multi_line \
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"Attaching after .* vfork to child .*" \
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".*New inferior 2 .*" \
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".* is executing new program: .*" \
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".*Inferior 2 .* exited normally.*"]
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} else {
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gdb_test "continue" \
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[multi_line \
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"Attaching after .* vfork to child .*" \
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".*New inferior 2 .*" \
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".*Detaching vfork parent process .* after child exec.*" \
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".*Inferior 1 .* detached.*" \
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".*is executing new program: .*" \
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".*Inferior 2 .*exited normally.*"]
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}
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}
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foreach_with_prefix detach-on-fork {"off" "on"} {
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test_vfork ${detach-on-fork}
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}
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@ -0,0 +1,52 @@
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/* This testcase is part of GDB, the GNU debugger.
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Copyright 2019 Free Software Foundation, Inc.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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#include <stdio.h>
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#include <unistd.h>
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#include <pthread.h>
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static void *
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f (void *arg)
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{
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int res = vfork ();
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if (res == -1)
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{
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perror ("vfork");
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return NULL;
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}
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else if (res == 0)
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{
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/* Child. */
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_exit (0);
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}
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else
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{
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/* Parent. */
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return NULL;
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}
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}
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int
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main (void)
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{
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pthread_t tid;
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pthread_create (&tid, NULL, f, NULL);
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pthread_join (tid, NULL);
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return 0;
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}
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@ -0,0 +1,60 @@
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# Copyright (C) 2019 Free Software Foundation, Inc.
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 3 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program. If not, see <http://www.gnu.org/licenses/>. */
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# Test following a vfork child that exits, when the vfork parent is a
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# threaded program, and it's a non-main thread that vforks.
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standard_testfile
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if {[build_executable "failed to prepare" $testfile $srcfile {debug pthreads}]} {
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return -1
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}
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# DETACH indicates whether "set detach-on-fork" is enabled. It is
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# either "on" or "off".
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proc test_vfork {detach} {
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global binfile
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clean_restart $binfile
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if ![runto_main] then {
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fail "can't run to main"
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return 0
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}
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gdb_test_no_output "set follow-fork-mode child"
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gdb_test_no_output "set detach-on-fork $detach"
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if {$detach == "off"} {
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gdb_test "continue" \
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[multi_line \
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"Attaching after .* vfork to child .*" \
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".*New inferior 2 .*" \
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".*Inferior 2 .*exited normally.*"]
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} else {
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gdb_test "continue" \
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[multi_line \
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"Attaching after .* vfork to child .*" \
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".*New inferior 2 .*" \
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".*Detaching vfork parent process .* after child exit.*" \
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".*Inferior 1 .* detached.*" \
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".*Inferior 2 .*exited normally.*"]
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}
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}
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foreach_with_prefix detach-on-fork {"off" "on"} {
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test_vfork ${detach-on-fork}
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}
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