559 lines
16 KiB
C
559 lines
16 KiB
C
/* Fork a Unix child process, and set up to debug it, for GDB.
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Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998, 1999, 2000,
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2001, 2004, 2005, 2006, 2007, 2008 Free Software Foundation, Inc.
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Contributed by Cygnus Support.
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This file is part of GDB.
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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 "defs.h"
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#include "gdb_string.h"
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#include "frame.h" /* required by inferior.h */
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#include "inferior.h"
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#include "target.h"
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#include "gdb_wait.h"
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#include "gdb_vfork.h"
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#include "gdbcore.h"
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#include "terminal.h"
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#include "gdbthread.h"
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#include "command.h" /* for dont_repeat () */
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#include "gdbcmd.h"
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#include "solib.h"
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#include <signal.h>
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/* This just gets used as a default if we can't find SHELL. */
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#define SHELL_FILE "/bin/sh"
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extern char **environ;
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static char *exec_wrapper;
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/* Break up SCRATCH into an argument vector suitable for passing to
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execvp and store it in ARGV. E.g., on "run a b c d" this routine
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would get as input the string "a b c d", and as output it would
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fill in ARGV with the four arguments "a", "b", "c", "d". */
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static void
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breakup_args (char *scratch, char **argv)
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{
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char *cp = scratch;
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for (;;)
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{
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/* Scan past leading separators */
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while (*cp == ' ' || *cp == '\t' || *cp == '\n')
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cp++;
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/* Break if at end of string. */
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if (*cp == '\0')
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break;
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/* Take an arg. */
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*argv++ = cp;
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/* Scan for next arg separator. */
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cp = strchr (cp, ' ');
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if (cp == NULL)
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cp = strchr (cp, '\t');
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if (cp == NULL)
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cp = strchr (cp, '\n');
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/* No separators => end of string => break. */
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if (cp == NULL)
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break;
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/* Replace the separator with a terminator. */
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*cp++ = '\0';
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}
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/* Null-terminate the vector. */
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*argv = NULL;
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}
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/* When executing a command under the given shell, return non-zero if
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the '!' character should be escaped when embedded in a quoted
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command-line argument. */
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static int
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escape_bang_in_quoted_argument (const char *shell_file)
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{
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const int shell_file_len = strlen (shell_file);
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/* Bang should be escaped only in C Shells. For now, simply check
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that the shell name ends with 'csh', which covers at least csh
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and tcsh. This should be good enough for now. */
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if (shell_file_len < 3)
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return 0;
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if (shell_file[shell_file_len - 3] == 'c'
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&& shell_file[shell_file_len - 2] == 's'
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&& shell_file[shell_file_len - 1] == 'h')
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return 1;
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return 0;
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}
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/* Start an inferior Unix child process and sets inferior_ptid to its
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pid. EXEC_FILE is the file to run. ALLARGS is a string containing
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the arguments to the program. ENV is the environment vector to
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pass. SHELL_FILE is the shell file, or NULL if we should pick
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one. */
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/* This function is NOT reentrant. Some of the variables have been
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made static to ensure that they survive the vfork call. */
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void
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fork_inferior (char *exec_file_arg, char *allargs, char **env,
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void (*traceme_fun) (void), void (*init_trace_fun) (int),
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void (*pre_trace_fun) (void), char *shell_file_arg)
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{
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int pid;
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char *shell_command;
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static char default_shell_file[] = SHELL_FILE;
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int len;
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/* Set debug_fork then attach to the child while it sleeps, to debug. */
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static int debug_fork = 0;
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/* This is set to the result of setpgrp, which if vforked, will be visible
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to you in the parent process. It's only used by humans for debugging. */
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static int debug_setpgrp = 657473;
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static char *shell_file;
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static char *exec_file;
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char **save_our_env;
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int shell = 0;
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static char **argv;
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const char *inferior_io_terminal = get_inferior_io_terminal ();
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/* If no exec file handed to us, get it from the exec-file command
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-- with a good, common error message if none is specified. */
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exec_file = exec_file_arg;
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if (exec_file == 0)
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exec_file = get_exec_file (1);
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/* STARTUP_WITH_SHELL is defined in inferior.h. If 0,e we'll just
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do a fork/exec, no shell, so don't bother figuring out what
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shell. */
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shell_file = shell_file_arg;
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if (STARTUP_WITH_SHELL)
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{
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/* Figure out what shell to start up the user program under. */
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if (shell_file == NULL)
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shell_file = getenv ("SHELL");
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if (shell_file == NULL)
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shell_file = default_shell_file;
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shell = 1;
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}
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/* Multiplying the length of exec_file by 4 is to account for the
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fact that it may expand when quoted; it is a worst-case number
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based on every character being '. */
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len = 5 + 4 * strlen (exec_file) + 1 + strlen (allargs) + 1 + /*slop */ 12;
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if (exec_wrapper)
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len += strlen (exec_wrapper) + 1;
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shell_command = (char *) alloca (len);
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shell_command[0] = '\0';
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if (!shell)
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{
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/* We're going to call execvp. Create argument vector.
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Calculate an upper bound on the length of the vector by
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assuming that every other character is a separate
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argument. */
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int argc = (strlen (allargs) + 1) / 2 + 2;
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argv = (char **) xmalloc (argc * sizeof (*argv));
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argv[0] = exec_file;
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breakup_args (allargs, &argv[1]);
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}
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else
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{
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/* We're going to call a shell. */
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char *p;
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int need_to_quote;
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const int escape_bang = escape_bang_in_quoted_argument (shell_file);
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strcat (shell_command, "exec ");
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/* Add any exec wrapper. That may be a program name with arguments, so
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the user must handle quoting. */
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if (exec_wrapper)
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{
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strcat (shell_command, exec_wrapper);
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strcat (shell_command, " ");
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}
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/* Now add exec_file, quoting as necessary. */
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/* Quoting in this style is said to work with all shells. But
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csh on IRIX 4.0.1 can't deal with it. So we only quote it if
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we need to. */
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p = exec_file;
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while (1)
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{
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switch (*p)
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{
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case '\'':
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case '!':
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case '"':
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case '(':
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case ')':
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case '$':
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case '&':
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case ';':
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case '<':
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case '>':
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case ' ':
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case '\n':
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case '\t':
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need_to_quote = 1;
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goto end_scan;
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case '\0':
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need_to_quote = 0;
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goto end_scan;
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default:
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break;
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}
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++p;
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}
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end_scan:
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if (need_to_quote)
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{
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strcat (shell_command, "'");
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for (p = exec_file; *p != '\0'; ++p)
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{
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if (*p == '\'')
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strcat (shell_command, "'\\''");
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else if (*p == '!' && escape_bang)
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strcat (shell_command, "\\!");
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else
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strncat (shell_command, p, 1);
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}
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strcat (shell_command, "'");
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}
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else
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strcat (shell_command, exec_file);
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strcat (shell_command, " ");
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strcat (shell_command, allargs);
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}
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/* On some systems an exec will fail if the executable is open. */
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close_exec_file ();
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/* Retain a copy of our environment variables, since the child will
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replace the value of environ and if we're vforked, we have to
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restore it. */
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save_our_env = environ;
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/* Tell the terminal handling subsystem what tty we plan to run on;
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it will just record the information for later. */
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new_tty_prefork (inferior_io_terminal);
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/* It is generally good practice to flush any possible pending stdio
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output prior to doing a fork, to avoid the possibility of both
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the parent and child flushing the same data after the fork. */
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gdb_flush (gdb_stdout);
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gdb_flush (gdb_stderr);
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/* If there's any initialization of the target layers that must
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happen to prepare to handle the child we're about fork, do it
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now... */
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if (pre_trace_fun != NULL)
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(*pre_trace_fun) ();
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/* Create the child process. Since the child process is going to
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exec(3) shortly afterwards, try to reduce the overhead by
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calling vfork(2). However, if PRE_TRACE_FUN is non-null, it's
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likely that this optimization won't work since there's too much
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work to do between the vfork(2) and the exec(3). This is known
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to be the case on ttrace(2)-based HP-UX, where some handshaking
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between parent and child needs to happen between fork(2) and
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exec(2). However, since the parent is suspended in the vforked
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state, this doesn't work. Also note that the vfork(2) call might
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actually be a call to fork(2) due to the fact that autoconf will
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``#define vfork fork'' on certain platforms. */
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if (pre_trace_fun || debug_fork)
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pid = fork ();
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else
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pid = vfork ();
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if (pid < 0)
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perror_with_name (("vfork"));
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if (pid == 0)
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{
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if (debug_fork)
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sleep (debug_fork);
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/* Create a new session for the inferior process, if necessary.
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It will also place the inferior in a separate process group. */
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if (create_tty_session () <= 0)
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{
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/* No session was created, but we still want to run the inferior
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in a separate process group. */
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debug_setpgrp = gdb_setpgid ();
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if (debug_setpgrp == -1)
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perror ("setpgrp failed in child");
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}
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/* Ask the tty subsystem to switch to the one we specified
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earlier (or to share the current terminal, if none was
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specified). */
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new_tty ();
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/* Changing the signal handlers for the inferior after
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a vfork can also change them for the superior, so we don't mess
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with signals here. See comments in
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initialize_signals for how we get the right signal handlers
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for the inferior. */
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/* "Trace me, Dr. Memory!" */
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(*traceme_fun) ();
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/* The call above set this process (the "child") as debuggable
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by the original gdb process (the "parent"). Since processes
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(unlike people) can have only one parent, if you are debugging
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gdb itself (and your debugger is thus _already_ the
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controller/parent for this child), code from here on out is
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undebuggable. Indeed, you probably got an error message
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saying "not parent". Sorry; you'll have to use print
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statements! */
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/* There is no execlpe call, so we have to set the environment
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for our child in the global variable. If we've vforked, this
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clobbers the parent, but environ is restored a few lines down
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in the parent. By the way, yes we do need to look down the
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path to find $SHELL. Rich Pixley says so, and I agree. */
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environ = env;
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/* If we decided above to start up with a shell, we exec the
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shell, "-c" says to interpret the next arg as a shell command
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to execute, and this command is "exec <target-program>
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<args>". */
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if (shell)
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{
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execlp (shell_file, shell_file, "-c", shell_command, (char *) 0);
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/* If we get here, it's an error. */
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fprintf_unfiltered (gdb_stderr, "Cannot exec %s: %s.\n", shell_file,
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safe_strerror (errno));
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gdb_flush (gdb_stderr);
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_exit (0177);
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}
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else
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{
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/* Otherwise, we directly exec the target program with
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execvp. */
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int i;
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char *errstring;
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execvp (exec_file, argv);
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/* If we get here, it's an error. */
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errstring = safe_strerror (errno);
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fprintf_unfiltered (gdb_stderr, "Cannot exec %s ", exec_file);
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i = 1;
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while (argv[i] != NULL)
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{
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if (i != 1)
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fprintf_unfiltered (gdb_stderr, " ");
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fprintf_unfiltered (gdb_stderr, "%s", argv[i]);
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i++;
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}
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fprintf_unfiltered (gdb_stderr, ".\n");
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#if 0
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/* This extra info seems to be useless. */
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fprintf_unfiltered (gdb_stderr, "Got error %s.\n", errstring);
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#endif
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gdb_flush (gdb_stderr);
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_exit (0177);
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}
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}
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/* Restore our environment in case a vforked child clob'd it. */
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environ = save_our_env;
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init_thread_list ();
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add_inferior (pid);
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/* Needed for wait_for_inferior stuff below. */
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inferior_ptid = pid_to_ptid (pid);
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/* We have something that executes now. We'll be running through
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the shell at this point, but the pid shouldn't change. Targets
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supporting MT should fill this task's ptid with more data as soon
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as they can. */
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add_thread_silent (inferior_ptid);
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/* Now that we have a child process, make it our target, and
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initialize anything target-vector-specific that needs
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initializing. */
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(*init_trace_fun) (pid);
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/* We are now in the child process of interest, having exec'd the
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correct program, and are poised at the first instruction of the
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new program. */
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}
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/* Accept NTRAPS traps from the inferior. */
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void
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startup_inferior (int ntraps)
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{
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int pending_execs = ntraps;
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int terminal_initted = 0;
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/* The process was started by the fork that created it, but it will
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have stopped one instruction after execing the shell. Here we
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must get it up to actual execution of the real program. */
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if (exec_wrapper)
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pending_execs++;
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while (1)
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{
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int resume_signal = TARGET_SIGNAL_0;
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ptid_t resume_ptid;
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ptid_t event_ptid;
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struct target_waitstatus ws;
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memset (&ws, 0, sizeof (ws));
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event_ptid = target_wait (pid_to_ptid (-1), &ws);
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if (ws.kind == TARGET_WAITKIND_IGNORE)
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/* The inferior didn't really stop, keep waiting. */
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continue;
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switch (ws.kind)
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{
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case TARGET_WAITKIND_SPURIOUS:
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case TARGET_WAITKIND_LOADED:
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case TARGET_WAITKIND_FORKED:
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case TARGET_WAITKIND_VFORKED:
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case TARGET_WAITKIND_SYSCALL_ENTRY:
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case TARGET_WAITKIND_SYSCALL_RETURN:
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/* Ignore gracefully during startup of the inferior. */
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switch_to_thread (event_ptid);
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break;
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case TARGET_WAITKIND_SIGNALLED:
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target_terminal_ours ();
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target_mourn_inferior ();
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error (_("During startup program terminated with signal %s, %s."),
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target_signal_to_name (ws.value.sig),
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target_signal_to_string (ws.value.sig));
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return;
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case TARGET_WAITKIND_EXITED:
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target_terminal_ours ();
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target_mourn_inferior ();
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if (ws.value.integer)
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error (_("During startup program exited with code %d."),
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ws.value.integer);
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else
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error (_("During startup program exited normally."));
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return;
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case TARGET_WAITKIND_EXECD:
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/* Handle EXEC signals as if they were SIGTRAP signals. */
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xfree (ws.value.execd_pathname);
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resume_signal = TARGET_SIGNAL_TRAP;
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switch_to_thread (event_ptid);
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break;
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case TARGET_WAITKIND_STOPPED:
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resume_signal = ws.value.sig;
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switch_to_thread (event_ptid);
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break;
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}
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/* In all-stop mode, resume all threads. */
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if (!non_stop)
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resume_ptid = pid_to_ptid (-1);
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else
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resume_ptid = event_ptid;
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if (resume_signal != TARGET_SIGNAL_TRAP)
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{
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/* Let shell child handle its own signals in its own way. */
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target_resume (resume_ptid, 0, resume_signal);
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}
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else
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{
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/* We handle SIGTRAP, however; it means child did an exec. */
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if (!terminal_initted)
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{
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/* Now that the child has exec'd we know it has already
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set its process group. On POSIX systems, tcsetpgrp
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will fail with EPERM if we try it before the child's
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setpgid. */
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/* Set up the "saved terminal modes" of the inferior
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based on what modes we are starting it with. */
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target_terminal_init ();
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/* Install inferior's terminal modes. */
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target_terminal_inferior ();
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terminal_initted = 1;
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}
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if (--pending_execs == 0)
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break;
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/* Just make it go on. */
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target_resume (resume_ptid, 0, TARGET_SIGNAL_0);
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}
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}
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/* Mark all threads non-executing. */
|
|
set_executing (pid_to_ptid (-1), 0);
|
|
|
|
stop_pc = read_pc ();
|
|
}
|
|
|
|
/* Implement the "unset exec-wrapper" command. */
|
|
|
|
static void
|
|
unset_exec_wrapper_command (char *args, int from_tty)
|
|
{
|
|
xfree (exec_wrapper);
|
|
exec_wrapper = NULL;
|
|
}
|
|
|
|
void
|
|
_initialize_fork_child (void)
|
|
{
|
|
add_setshow_filename_cmd ("exec-wrapper", class_run, &exec_wrapper, _("\
|
|
Set a wrapper for running programs.\n\
|
|
The wrapper prepares the system and environment for the new program."),
|
|
_("\
|
|
Show the wrapper for running programs."), NULL,
|
|
NULL, NULL,
|
|
&setlist, &showlist);
|
|
|
|
add_cmd ("exec-wrapper", class_run, unset_exec_wrapper_command,
|
|
_("Disable use of an execution wrapper."),
|
|
&unsetlist);
|
|
}
|