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Handle fork() failures more gracefully

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This commit is contained in:
Kovid Goyal 2018-01-05 13:57:49 +05:30
parent e03c713294
commit f06f871dfc
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GPG Key ID: 06BC317B515ACE7C
1 changed files with 42 additions and 35 deletions
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77
kitty/child.c
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@ -51,45 +51,52 @@ spawn(PyObject *self UNUSED, PyObject *args) {
#define exit_on_err(m) { write_to_stderr(m); write_to_stderr(": "); write_to_stderr(strerror(errno)); exit(EXIT_FAILURE); }
pid_t pid = fork();
if (pid == 0) {
// child
// Use only signal-safe functions (man 7 signal-safety)
if (chdir(cwd) != 0) { if (chdir("/") != 0) {} }; // ignore failure to chdir to /
if (setsid() == -1) exit_on_err("setsid() in child process failed");
if (dup2(slave, 1) == -1) exit_on_err("dup2() failed for fd number 1");
if (dup2(slave, 2) == -1) exit_on_err("dup2() failed for fd number 2");
if (stdin_read_fd > -1) {
if (dup2(stdin_read_fd, 0) == -1) exit_on_err("dup2() failed for fd number 0");
close(stdin_read_fd);
close(stdin_write_fd);
} else {
if (dup2(slave, 0) == -1) exit_on_err("dup2() failed for fd number 0");
}
close(slave);
close(master);
for (int c = 3; c < 201; c++) close(c);
switch(pid) {
case 0:
// child
// Use only signal-safe functions (man 7 signal-safety)
if (chdir(cwd) != 0) { if (chdir("/") != 0) {} }; // ignore failure to chdir to /
if (setsid() == -1) exit_on_err("setsid() in child process failed");
if (dup2(slave, 1) == -1) exit_on_err("dup2() failed for fd number 1");
if (dup2(slave, 2) == -1) exit_on_err("dup2() failed for fd number 2");
if (stdin_read_fd > -1) {
if (dup2(stdin_read_fd, 0) == -1) exit_on_err("dup2() failed for fd number 0");
close(stdin_read_fd);
close(stdin_write_fd);
} else {
if (dup2(slave, 0) == -1) exit_on_err("dup2() failed for fd number 0");
}
close(slave);
close(master);
for (int c = 3; c < 201; c++) close(c);
// Establish the controlling terminal (see man 7 credentials)
int tfd = open(name, O_RDWR);
if (tfd == -1) exit_on_err("Failed to open controlling terminal");
close(tfd);
// Establish the controlling terminal (see man 7 credentials)
int tfd = open(name, O_RDWR);
if (tfd == -1) exit_on_err("Failed to open controlling terminal");
close(tfd);
environ = env;
execvp(argv[0], argv);
// Report the failure and exec a shell instead, so that we are not left
// with a forked but not exec'ed process
write_to_stderr("Failed to launch child: ");
write_to_stderr(argv[0]);
write_to_stderr("\nWith error: ");
write_to_stderr(strerror(errno));
write_to_stderr("\nPress Enter to exit.\n");
execlp("sh", "sh", "-c", "read w", NULL);
exit(EXIT_FAILURE);
} else {
free(argv);
free(env);
environ = env;
execvp(argv[0], argv);
// Report the failure and exec a shell instead, so that we are not left
// with a forked but not exec'ed process
write_to_stderr("Failed to launch child: ");
write_to_stderr(argv[0]);
write_to_stderr("\nWith error: ");
write_to_stderr(strerror(errno));
write_to_stderr("\nPress Enter to exit.\n");
execlp("sh", "sh", "-c", "read w", NULL);
exit(EXIT_FAILURE);
break;
case -1:
PyErr_SetFromErrno(PyExc_OSError);
break;
default:
break;
}
#undef exit_on_err
free(argv);
free(env);
if (pid == -1) return NULL;
return PyLong_FromLong(pid);
}