[Telemetry] Add timeout to telemetry run_tests

tools/telemetry/third_party/subprocess32/_posixsubprocess.c

+/* Authors: Gregory P. Smith & Jeffrey Yasskin */
+#define PY_SSIZE_T_CLEAN
+#include "Python.h"
+#if defined(__linux__) && !defined(HAVE_PIPE2)
+# define HAVE_PIPE2 1  /* From 3.2's configure script, undef if you don't. */
+#endif
+#if defined(HAVE_PIPE2) && !defined(_GNU_SOURCE)
+# define _GNU_SOURCE
+#endif
+#include <unistd.h>
+#include <fcntl.h>
+#ifdef __linux__
+# define HAVE_SYS_TYPES_H 1  /* From 3.2's configure script, undef if reqd. */
+# define HAVE_SYS_SYSCALL_H 1  /* From 3.2's configure script, undef if reqd. */
+# define HAVE_SYS_DIRENT_H 1  /* From 3.2's configure script, undef if reqd. */
+#endif
+#ifdef HAVE_SYS_TYPES_H
+#include <sys/types.h>
+#endif
+#if defined(HAVE_SYS_STAT_H) && defined(__FreeBSD__)
+#include <sys/stat.h>
+#endif
+#ifdef HAVE_SYS_SYSCALL_H
+#include <sys/syscall.h>
+#endif
+#ifdef HAVE_DIRENT_H
+#include <dirent.h>
+#endif
+
+#if defined(__ANDROID__) && !defined(SYS_getdents64)
+/* Android doesn't expose syscalls, add the definition manually. */
+# include <sys/linux-syscalls.h>
+# define SYS_getdents64  __NR_getdents64
+#endif
+
+#include "_posixsubprocess_helpers.c"
+
+#if (PY_VERSION_HEX < 0x02060300)
+/* These are not public API fuctions until 2.6.3. */
+static void _PyImport_AcquireLock(void);
+static int _PyImport_ReleaseLock(void);
+#endif
+
+#if defined(sun)
+/* readdir64 is used to work around Solaris 9 bug 6395699. */
+# define readdir readdir64
+# define dirent dirent64
+# if !defined(HAVE_DIRFD)
+/* Some versions of Solaris lack dirfd(). */
+#  define dirfd(dirp) ((dirp)->dd_fd)
+#  define HAVE_DIRFD
+# endif
+#endif
+
+#if defined(__FreeBSD__) || (defined(__APPLE__) && defined(__MACH__))
+# define FD_DIR "/dev/fd"
+#else
+# define FD_DIR "/proc/self/fd"
+#endif
+
+#define POSIX_CALL(call)   if ((call) == -1) goto error
+
+
+/* Maximum file descriptor, initialized on module load. */
+static long max_fd;
+
+
+/* Given the gc module call gc.enable() and return 0 on success. */
+static int
+_enable_gc(PyObject *gc_module)
+{
+    PyObject *result;
+    result = PyObject_CallMethod(gc_module, "enable", NULL);
+    if (result == NULL)
+        return 1;
+    Py_DECREF(result);
+    return 0;
+}
+
+
+/* Convert ASCII to a positive int, no libc call. no overflow. -1 on error. */
+static int
+_pos_int_from_ascii(char *name)
+{
+    int num = 0;
+    while (*name >= '0' && *name <= '9') {
+        num = num * 10 + (*name - '0');
+        ++name;
+    }
+    if (*name)
+        return -1;  /* Non digit found, not a number. */
+    return num;
+}
+
+
+#if defined(__FreeBSD__)
+/* When /dev/fd isn't mounted it is often a static directory populated
+ * with 0 1 2 or entries for 0 .. 63 on FreeBSD, NetBSD and OpenBSD.
+ * NetBSD and OpenBSD have a /proc fs available (though not necessarily
+ * mounted) and do not have fdescfs for /dev/fd.  MacOS X has a devfs
+ * that properly supports /dev/fd.
+ */
+static int
+_is_fdescfs_mounted_on_dev_fd()
+{
+    struct stat dev_stat;
+    struct stat dev_fd_stat;
+    if (stat("/dev", &dev_stat) != 0)
+        return 0;
+    if (stat(FD_DIR, &dev_fd_stat) != 0)
+        return 0; 
+    if (dev_stat.st_dev == dev_fd_stat.st_dev)
+        return 0;  /* / == /dev == /dev/fd means it is static. #fail */
+    return 1;
+}
+#endif
+
+
+/* Returns 1 if there is a problem with fd_sequence, 0 otherwise. */
+static int
+_sanity_check_python_fd_sequence(PyObject *fd_sequence)
+{
+    Py_ssize_t seq_idx, seq_len = PySequence_Length(fd_sequence);
+    long prev_fd = -1;
+    for (seq_idx = 0; seq_idx < seq_len; ++seq_idx) {
+        PyObject* py_fd = PySequence_Fast_GET_ITEM(fd_sequence, seq_idx);
+        long iter_fd = PyLong_AsLong(py_fd);
+        if (iter_fd < 0 || iter_fd < prev_fd || iter_fd > INT_MAX) {
+            /* Negative, overflow, not a Long, unsorted, too big for a fd. */
+            return 1;
+        }
+    }
+    return 0;
+}
+
+
+/* Is fd found in the sorted Python Sequence? */
+static int
+_is_fd_in_sorted_fd_sequence(int fd, PyObject *fd_sequence)
+{
+    /* Binary search. */
+    Py_ssize_t search_min = 0;
+    Py_ssize_t search_max = PySequence_Length(fd_sequence) - 1;
+    if (search_max < 0)
+        return 0;
+    do {
+        long middle = (search_min + search_max) / 2;
+        long middle_fd = PyLong_AsLong(
+                PySequence_Fast_GET_ITEM(fd_sequence, middle));
+        if (fd == middle_fd)
+            return 1;
+        if (fd > middle_fd)
+            search_min = middle + 1;
+        else
+            search_max = middle - 1;
+    } while (search_min <= search_max);
+    return 0;
+}
+
+
+/* Close all file descriptors in the range start_fd inclusive to
+ * end_fd exclusive except for those in py_fds_to_keep.  If the
+ * range defined by [start_fd, end_fd) is large this will take a
+ * long time as it calls close() on EVERY possible fd.
+ */
+static void
+_close_fds_by_brute_force(int start_fd, int end_fd, PyObject *py_fds_to_keep)
+{
+    Py_ssize_t num_fds_to_keep = PySequence_Length(py_fds_to_keep);
+    Py_ssize_t keep_seq_idx;
+    int fd_num;
+    /* As py_fds_to_keep is sorted we can loop through the list closing
+     * fds inbetween any in the keep list falling within our range. */
+    for (keep_seq_idx = 0; keep_seq_idx < num_fds_to_keep; ++keep_seq_idx) {
+        PyObject* py_keep_fd = PySequence_Fast_GET_ITEM(py_fds_to_keep,
+                                                        keep_seq_idx);
+        int keep_fd = PyLong_AsLong(py_keep_fd);
+        if (keep_fd < start_fd)
+            continue;
+        for (fd_num = start_fd; fd_num < keep_fd; ++fd_num) {
+            while (close(fd_num) < 0 && errno == EINTR);
+        }
+        start_fd = keep_fd + 1;
+    }
+    if (start_fd <= end_fd) {
+        for (fd_num = start_fd; fd_num < end_fd; ++fd_num) {
+            while (close(fd_num) < 0 && errno == EINTR);
+        }
+    }
+}
+
+
+#if defined(__linux__) && defined(HAVE_SYS_SYSCALL_H)
+/* It doesn't matter if d_name has room for NAME_MAX chars; we're using this
+ * only to read a directory of short file descriptor number names.  The kernel
+ * will return an error if we didn't give it enough space.  Highly Unlikely.
+ * This structure is very old and stable: It will not change unless the kernel
+ * chooses to break compatibility with all existing binaries.  Highly Unlikely.
+ */
+struct linux_dirent64 {
+   unsigned long long d_ino;
+   long long d_off;
+   unsigned short d_reclen;     /* Length of this linux_dirent */
+   unsigned char  d_type;
+   char           d_name[256];  /* Filename (null-terminated) */
+};
+
+/* Close all open file descriptors in the range start_fd inclusive to end_fd
+ * exclusive. Do not close any in the sorted py_fds_to_keep list.
+ *
+ * This version is async signal safe as it does not make any unsafe C library
+ * calls, malloc calls or handle any locks.  It is _unfortunate_ to be forced
+ * to resort to making a kernel system call directly but this is the ONLY api
+ * available that does no harm.  opendir/readdir/closedir perform memory
+ * allocation and locking so while they usually work they are not guaranteed
+ * to (especially if you have replaced your malloc implementation).  A version
+ * of this function that uses those can be found in the _maybe_unsafe variant.
+ *
+ * This is Linux specific because that is all I am ready to test it on.  It
+ * should be easy to add OS specific dirent or dirent64 structures and modify
+ * it with some cpp #define magic to work on other OSes as well if you want.
+ */
+static void
+_close_open_fd_range_safe(int start_fd, int end_fd, PyObject* py_fds_to_keep)
+{
+    int fd_dir_fd;
+    if (start_fd >= end_fd)
+        return;
+#ifdef O_CLOEXEC
+    fd_dir_fd = open(FD_DIR, O_RDONLY | O_CLOEXEC, 0);
+#else
+    fd_dir_fd = open(FD_DIR, O_RDONLY, 0);
+#ifdef FD_CLOEXEC
+    {
+        int old = fcntl(fd_dir_fd, F_GETFD);
+        if (old != -1)
+            fcntl(fd_dir_fd, F_SETFD, old | FD_CLOEXEC);
+    }
+#endif
+#endif
+    if (fd_dir_fd == -1) {
+        /* No way to get a list of open fds. */
+        _close_fds_by_brute_force(start_fd, end_fd, py_fds_to_keep);
+        return;
+    } else {
+        char buffer[sizeof(struct linux_dirent64)];
+        int bytes;
+        while ((bytes = syscall(SYS_getdents64, fd_dir_fd,
+                                (struct linux_dirent64 *)buffer,
+                                sizeof(buffer))) > 0) {
+            struct linux_dirent64 *entry;
+            int offset;
+            for (offset = 0; offset < bytes; offset += entry->d_reclen) {
+                int fd;
+                entry = (struct linux_dirent64 *)(buffer + offset);
+                if ((fd = _pos_int_from_ascii(entry->d_name)) < 0)
+                    continue;  /* Not a number. */
+                if (fd != fd_dir_fd && fd >= start_fd && fd < end_fd &&
+                    !_is_fd_in_sorted_fd_sequence(fd, py_fds_to_keep)) {
+                    while (close(fd) < 0 && errno == EINTR);
+                }
+            }
+        }
+        close(fd_dir_fd);
+    }
+}
+
+#define _close_open_fd_range _close_open_fd_range_safe
+
+#else  /* NOT (defined(__linux__) && defined(HAVE_SYS_SYSCALL_H)) */
+
+
+/* Close all open file descriptors in the range start_fd inclusive to end_fd
+ * exclusive. Do not close any in the sorted py_fds_to_keep list.
+ *
+ * This function violates the strict use of async signal safe functions. :(
+ * It calls opendir(), readdir() and closedir().  Of these, the one most
+ * likely to ever cause a problem is opendir() as it performs an internal
+ * malloc().  Practically this should not be a problem.  The Java VM makes the
+ * same calls between fork and exec in its own UNIXProcess_md.c implementation.
+ *
+ * readdir_r() is not used because it provides no benefit.  It is typically
+ * implemented as readdir() followed by memcpy().  See also:
+ *   http://womble.decadent.org.uk/readdir_r-advisory.html
+ */
+static void
+_close_open_fd_range_maybe_unsafe(int start_fd, int end_fd,
+                                  PyObject* py_fds_to_keep)
+{
+    DIR *proc_fd_dir;
+#ifndef HAVE_DIRFD
+    while (_is_fd_in_sorted_fd_sequence(start_fd, py_fds_to_keep) &&
+           (start_fd < end_fd)) {
+        ++start_fd;
+    }
+    if (start_fd >= end_fd)
+        return;
+    /* Close our lowest fd before we call opendir so that it is likely to
+     * reuse that fd otherwise we might close opendir's file descriptor in
+     * our loop.  This trick assumes that fd's are allocated on a lowest
+     * available basis. */
+    while (close(start_fd) < 0 && errno == EINTR);
+    ++start_fd;
+#endif
+    if (start_fd >= end_fd)
+        return;
+
+#if defined(__FreeBSD__)
+    if (!_is_fdescfs_mounted_on_dev_fd())
+        proc_fd_dir = NULL;
+    else
+#endif
+        proc_fd_dir = opendir(FD_DIR);
+    if (!proc_fd_dir) {
+        /* No way to get a list of open fds. */
+        _close_fds_by_brute_force(start_fd, end_fd, py_fds_to_keep);
+    } else {
+        struct dirent *dir_entry;
+#ifdef HAVE_DIRFD
+        int fd_used_by_opendir = dirfd(proc_fd_dir);
+#else
+        int fd_used_by_opendir = start_fd - 1;
+#endif
+        errno = 0;
+        while ((dir_entry = readdir(proc_fd_dir))) {
+            int fd;
+            if ((fd = _pos_int_from_ascii(dir_entry->d_name)) < 0)
+                continue;  /* Not a number. */
+            if (fd != fd_used_by_opendir && fd >= start_fd && fd < end_fd &&
+                !_is_fd_in_sorted_fd_sequence(fd, py_fds_to_keep)) {
+                while (close(fd) < 0 && errno == EINTR);
+            }
+            errno = 0;
+        }
+        if (errno) {
+            /* readdir error, revert behavior. Highly Unlikely. */
+            _close_fds_by_brute_force(start_fd, end_fd, py_fds_to_keep);
+        }
+        closedir(proc_fd_dir);
+    }
+}
+
+#define _close_open_fd_range _close_open_fd_range_maybe_unsafe
+
+#endif  /* else NOT (defined(__linux__) && defined(HAVE_SYS_SYSCALL_H)) */
+
+
+/*
+ * This function is code executed in the child process immediately after fork
+ * to set things up and call exec().
+ *
+ * All of the code in this function must only use async-signal-safe functions,
+ * listed at `man 7 signal` or
+ * http://www.opengroup.org/onlinepubs/009695399/functions/xsh_chap02_04.html.
+ *
+ * This restriction is documented at
+ * http://www.opengroup.org/onlinepubs/009695399/functions/fork.html.
+ */
+static void
+child_exec(char *const exec_array[],
+           char *const argv[],
+           char *const envp[],
+           const char *cwd,
+           int p2cread, int p2cwrite,
+           int c2pread, int c2pwrite,
+           int errread, int errwrite,
+           int errpipe_read, int errpipe_write,
+           int close_fds, int restore_signals,
+           int call_setsid,
+           PyObject *py_fds_to_keep,
+           PyObject *preexec_fn,
+           PyObject *preexec_fn_args_tuple)
+{
+    int i, saved_errno, unused, reached_preexec = 0;
+    PyObject *result;
+    const char* err_msg = "";
+    /* Buffer large enough to hold a hex integer.  We can't malloc. */
+    char hex_errno[sizeof(saved_errno)*2+1];
+
+    /* Close parent's pipe ends. */
+    if (p2cwrite != -1) {
+        POSIX_CALL(close(p2cwrite));
+    }
+    if (c2pread != -1) {
+        POSIX_CALL(close(c2pread));
+    }
+    if (errread != -1) {
+        POSIX_CALL(close(errread));
+    }
+    POSIX_CALL(close(errpipe_read));
+
+    /* When duping fds, if there arises a situation where one of the fds is
+       either 0, 1 or 2, it is possible that it is overwritten (#12607). */
+    if (c2pwrite == 0)
+        POSIX_CALL(c2pwrite = dup(c2pwrite));
+    if (errwrite == 0 || errwrite == 1)
+        POSIX_CALL(errwrite = dup(errwrite));
+
+    /* Dup fds for child.
+       dup2() removes the CLOEXEC flag but we must do it ourselves if dup2()
+       would be a no-op (issue #10806). */
+    if (p2cread == 0) {
+        int old = fcntl(p2cread, F_GETFD);
+        if (old != -1)
+            fcntl(p2cread, F_SETFD, old & ~FD_CLOEXEC);
+    } else if (p2cread != -1) {
+        POSIX_CALL(dup2(p2cread, 0));  /* stdin */
+    }
+    if (c2pwrite == 1) {
+        int old = fcntl(c2pwrite, F_GETFD);
+        if (old != -1)
+            fcntl(c2pwrite, F_SETFD, old & ~FD_CLOEXEC);
+    } else if (c2pwrite != -1) {
+        POSIX_CALL(dup2(c2pwrite, 1));  /* stdout */
+    }
+    if (errwrite == 2) {
+        int old = fcntl(errwrite, F_GETFD);
+        if (old != -1)
+            fcntl(errwrite, F_SETFD, old & ~FD_CLOEXEC);
+    } else if (errwrite != -1) {
+        POSIX_CALL(dup2(errwrite, 2));  /* stderr */
+    }
+
+    /* Close pipe fds.  Make sure we don't close the same fd more than */
+    /* once, or standard fds. */
+    if (p2cread > 2) {
+        POSIX_CALL(close(p2cread));
+    }
+    if (c2pwrite > 2 && c2pwrite != p2cread) {
+        POSIX_CALL(close(c2pwrite));
+    }
+    if (errwrite != c2pwrite && errwrite != p2cread && errwrite > 2) {
+        POSIX_CALL(close(errwrite));
+    }
+
+    if (cwd)
+        POSIX_CALL(chdir(cwd));
+
+    if (restore_signals)
+        _Py_RestoreSignals();
+
+#ifdef HAVE_SETSID
+    if (call_setsid)
+        POSIX_CALL(setsid());
+#endif
+
+    reached_preexec = 1;
+    if (preexec_fn != Py_None && preexec_fn_args_tuple) {
+        /* This is where the user has asked us to deadlock their program. */
+        result = PyObject_Call(preexec_fn, preexec_fn_args_tuple, NULL);
+        if (result == NULL) {
+            /* Stringifying the exception or traceback would involve
+             * memory allocation and thus potential for deadlock.
+             * We've already faced potential deadlock by calling back
+             * into Python in the first place, so it probably doesn't
+             * matter but we avoid it to minimize the possibility. */
+            err_msg = "Exception occurred in preexec_fn.";
+            errno = 0;  /* We don't want to report an OSError. */
+            goto error;
+        }
+        /* Py_DECREF(result); - We're about to exec so why bother? */
+    }
+
+    if (close_fds) {
+        int local_max_fd = max_fd;
+#if defined(__NetBSD__)
+        local_max_fd = fcntl(0, F_MAXFD);
+        if (local_max_fd < 0)
+            local_max_fd = max_fd;
+#endif
+        /* TODO HP-UX could use pstat_getproc() if anyone cares about it. */
+        _close_open_fd_range(3, local_max_fd, py_fds_to_keep);
+    }
+
+    /* This loop matches the Lib/os.py _execvpe()'s PATH search when */
+    /* given the executable_list generated by Lib/subprocess.py.     */
+    saved_errno = 0;
+    for (i = 0; exec_array[i] != NULL; ++i) {
+        const char *executable = exec_array[i];
+        if (envp) {
+            execve(executable, argv, envp);
+        } else {
+            execv(executable, argv);
+        }
+        if (errno != ENOENT && errno != ENOTDIR && saved_errno == 0) {
+            saved_errno = errno;
+        }
+    }
+    /* Report the first exec error, not the last. */
+    if (saved_errno)
+        errno = saved_errno;
+
+error:
+    saved_errno = errno;
+    /* Report the posix error to our parent process. */
+    /* We ignore all write() return values as the total size of our writes is
+     * less than PIPEBUF and we cannot do anything about an error anyways. */
+    if (saved_errno) {
+        char *cur;
+        unused = write(errpipe_write, "OSError:", 8);
+        cur = hex_errno + sizeof(hex_errno);
+        while (saved_errno != 0 && cur > hex_errno) {
+            *--cur = "0123456789ABCDEF"[saved_errno % 16];
+            saved_errno /= 16;
+        }
+        unused = write(errpipe_write, cur, hex_errno + sizeof(hex_errno) - cur);
+        unused = write(errpipe_write, ":", 1);
+        if (!reached_preexec) {
+            /* Indicate to the parent that the error happened before exec(). */
+            unused = write(errpipe_write, "noexec", 6);
+        }
+        /* We can't call strerror(saved_errno).  It is not async signal safe.
+         * The parent process will look the error message up. */
+    } else {
+        unused = write(errpipe_write, "RuntimeError:0:", 15);
+        unused = write(errpipe_write, err_msg, strlen(err_msg));
+    }
+    if (unused) return;  /* silly? yes! avoids gcc compiler warning. */
+}
+
+
+static PyObject *
+subprocess_fork_exec(PyObject* self, PyObject *args)
+{
+    PyObject *gc_module = NULL;
+    PyObject *executable_list, *py_close_fds, *py_fds_to_keep;
+    PyObject *env_list, *preexec_fn;
+    PyObject *process_args, *converted_args = NULL, *fast_args = NULL;
+    PyObject *preexec_fn_args_tuple = NULL;
+    int p2cread, p2cwrite, c2pread, c2pwrite, errread, errwrite;
+    int errpipe_read, errpipe_write, close_fds, restore_signals;
+    int call_setsid;
+    PyObject *cwd_obj, *cwd_obj2;
+    const char *cwd;
+    pid_t pid;
+    int need_to_reenable_gc = 0;
+    char *const *exec_array, *const *argv = NULL, *const *envp = NULL;
+    Py_ssize_t arg_num;
+
+    if (!PyArg_ParseTuple(
+            args, "OOOOOOiiiiiiiiiiO:fork_exec",
+            &process_args, &executable_list, &py_close_fds, &py_fds_to_keep,
+            &cwd_obj, &env_list,
+            &p2cread, &p2cwrite, &c2pread, &c2pwrite,
+            &errread, &errwrite, &errpipe_read, &errpipe_write,
+            &restore_signals, &call_setsid, &preexec_fn))
+        return NULL;
+
+    close_fds = PyObject_IsTrue(py_close_fds);
+    if (close_fds < 0)
+        return NULL;
+    if (close_fds && errpipe_write < 3) {  /* precondition */
+        PyErr_SetString(PyExc_ValueError, "errpipe_write must be >= 3");
+        return NULL;
+    }
+    if (PySequence_Length(py_fds_to_keep) < 0) {
+        PyErr_SetString(PyExc_ValueError, "cannot get length of fds_to_keep");
+        return NULL;
+    }
+    if (_sanity_check_python_fd_sequence(py_fds_to_keep)) {
+        PyErr_SetString(PyExc_ValueError, "bad value(s) in fds_to_keep");
+        return NULL;
+    }
+
+    /* We need to call gc.disable() when we'll be calling preexec_fn */
+    if (preexec_fn != Py_None) {
+        PyObject *result;
+        gc_module = PyImport_ImportModule("gc");
+        if (gc_module == NULL)
+            return NULL;
+        result = PyObject_CallMethod(gc_module, "isenabled", NULL);
+        if (result == NULL) {
+            Py_DECREF(gc_module);
+            return NULL;
+        }
+        need_to_reenable_gc = PyObject_IsTrue(result);
+        Py_DECREF(result);
+        if (need_to_reenable_gc == -1) {
+            Py_DECREF(gc_module);
+            return NULL;
+        }
+        result = PyObject_CallMethod(gc_module, "disable", NULL);
+        if (result == NULL) {
+            Py_DECREF(gc_module);
+            return NULL;
+        }
+        Py_DECREF(result);
+    }
+
+    exec_array = _PySequence_BytesToCharpArray(executable_list);
+    if (!exec_array) {
+        Py_XDECREF(gc_module);
+        return NULL;
+    }
+
+    /* Convert args and env into appropriate arguments for exec() */
+    /* These conversions are done in the parent process to avoid allocating
+       or freeing memory in the child process. */
+    if (process_args != Py_None) {
+        Py_ssize_t num_args;
+        /* Equivalent to:  */
+        /*  tuple(PyUnicode_FSConverter(arg) for arg in process_args)  */
+        fast_args = PySequence_Fast(process_args, "argv must be a tuple");
+        if (fast_args == NULL)
+            goto cleanup;
+        num_args = PySequence_Fast_GET_SIZE(fast_args);
+        converted_args = PyTuple_New(num_args);
+        if (converted_args == NULL)
+            goto cleanup;
+        for (arg_num = 0; arg_num < num_args; ++arg_num) {
+            PyObject *borrowed_arg, *converted_arg;
+            borrowed_arg = PySequence_Fast_GET_ITEM(fast_args, arg_num);
+            if (PyUnicode_FSConverter(borrowed_arg, &converted_arg) == 0)
+                goto cleanup;
+            PyTuple_SET_ITEM(converted_args, arg_num, converted_arg);
+        }
+
+        argv = _PySequence_BytesToCharpArray(converted_args);
+        Py_CLEAR(converted_args);
+        Py_CLEAR(fast_args);
+        if (!argv)
+            goto cleanup;
+    }
+
+    if (env_list != Py_None) {
+        envp = _PySequence_BytesToCharpArray(env_list);
+        if (!envp)
+            goto cleanup;
+    }
+
+    if (preexec_fn != Py_None) {
+        preexec_fn_args_tuple = PyTuple_New(0);
+        if (!preexec_fn_args_tuple)
+            goto cleanup;
+        _PyImport_AcquireLock();
+    }
+
+    if (cwd_obj != Py_None) {
+        if (PyUnicode_FSConverter(cwd_obj, &cwd_obj2) == 0)
+            goto cleanup;
+        cwd = PyString_AsString(cwd_obj2);
+    } else {
+        cwd = NULL;
+        cwd_obj2 = NULL;
+    }
+
+    pid = fork();
+    if (pid == 0) {
+        /* Child process */
+        /*
+         * Code from here to _exit() must only use async-signal-safe functions,
+         * listed at `man 7 signal` or
+         * http://www.opengroup.org/onlinepubs/009695399/functions/xsh_chap02_04.html.
+         */
+
+        if (preexec_fn != Py_None) {
+            /* We'll be calling back into Python later so we need to do this.
+             * This call may not be async-signal-safe but neither is calling
+             * back into Python.  The user asked us to use hope as a strategy
+             * to avoid deadlock... */
+            PyOS_AfterFork();
+        }
+
+        child_exec(exec_array, argv, envp, cwd,
+                   p2cread, p2cwrite, c2pread, c2pwrite,
+                   errread, errwrite, errpipe_read, errpipe_write,
+                   close_fds, restore_signals, call_setsid,
+                   py_fds_to_keep, preexec_fn, preexec_fn_args_tuple);
+        _exit(255);
+        return NULL;  /* Dead code to avoid a potential compiler warning. */
+    }
+    Py_XDECREF(cwd_obj2);
+
+    if (pid == -1) {
+        /* Capture the errno exception before errno can be clobbered. */
+        PyErr_SetFromErrno(PyExc_OSError);
+    }
+    if (preexec_fn != Py_None &&
+        _PyImport_ReleaseLock() < 0 && !PyErr_Occurred()) {
+        PyErr_SetString(PyExc_RuntimeError,
+                        "not holding the import lock");
+    }
+
+    /* Parent process */
+    if (envp)
+        _Py_FreeCharPArray(envp);
+    if (argv)
+        _Py_FreeCharPArray(argv);
+    _Py_FreeCharPArray(exec_array);
+
+    /* Reenable gc in the parent process (or if fork failed). */
+    if (need_to_reenable_gc && _enable_gc(gc_module)) {
+        Py_XDECREF(gc_module);
+        return NULL;
+    }
+    Py_XDECREF(preexec_fn_args_tuple);
+    Py_XDECREF(gc_module);
+
+    if (pid == -1)
+        return NULL;  /* fork() failed.  Exception set earlier. */
+
+    return PyLong_FromPid(pid);
+
+cleanup:
+    if (envp)
+        _Py_FreeCharPArray(envp);
+    if (argv)
+        _Py_FreeCharPArray(argv);
+    _Py_FreeCharPArray(exec_array);
+    Py_XDECREF(converted_args);
+    Py_XDECREF(fast_args);
+    Py_XDECREF(preexec_fn_args_tuple);
+
+    /* Reenable gc if it was disabled. */
+    if (need_to_reenable_gc)
+        _enable_gc(gc_module);
+    Py_XDECREF(gc_module);
+    return NULL;
+}
+
+
+PyDoc_STRVAR(subprocess_fork_exec_doc,
+"fork_exec(args, executable_list, close_fds, cwd, env,\n\
+          p2cread, p2cwrite, c2pread, c2pwrite,\n\
+          errread, errwrite, errpipe_read, errpipe_write,\n\
+          restore_signals, call_setsid, preexec_fn)\n\
+\n\
+Forks a child process, closes parent file descriptors as appropriate in the\n\
+child and dups the few that are needed before calling exec() in the child\n\
+process.\n\
+\n\
+The preexec_fn, if supplied, will be called immediately before exec.\n\
+WARNING: preexec_fn is NOT SAFE if your application uses threads.\n\
+         It may trigger infrequent, difficult to debug deadlocks.\n\
+\n\
+If an error occurs in the child process before the exec, it is\n\
+serialized and written to the errpipe_write fd per subprocess.py.\n\
+\n\
+Returns: the child process's PID.\n\
+\n\
+Raises: Only on an error in the parent process.\n\
+");
+
+PyDoc_STRVAR(subprocess_cloexec_pipe_doc,
+"cloexec_pipe() -> (read_end, write_end)\n\n\
+Create a pipe whose ends have the cloexec flag set; write_end will be >= 3.");
+
+static PyObject *
+subprocess_cloexec_pipe(PyObject *self, PyObject *noargs)
+{
+    int fds[2];
+    int res, saved_errno;
+    long oldflags;
+#ifdef HAVE_PIPE2
+    Py_BEGIN_ALLOW_THREADS
+    res = pipe2(fds, O_CLOEXEC);
+    Py_END_ALLOW_THREADS
+    if (res != 0 && errno == ENOSYS)
+    {
+#endif
+        /* We hold the GIL which offers some protection from other code calling
+         * fork() before the CLOEXEC flags have been set but we can't guarantee
+         * anything without pipe2(). */
+        res = pipe(fds);
+
+        if (res == 0) {
+            oldflags = fcntl(fds[0], F_GETFD, 0);
+            if (oldflags < 0) res = oldflags;
+        }
+        if (res == 0)
+            res = fcntl(fds[0], F_SETFD, oldflags | FD_CLOEXEC);
+
+        if (res == 0) {
+            oldflags = fcntl(fds[1], F_GETFD, 0);
+            if (oldflags < 0) res = oldflags;
+        }
+        if (res == 0)
+            res = fcntl(fds[1], F_SETFD, oldflags | FD_CLOEXEC);
+#ifdef HAVE_PIPE2
+    }
+#endif
+    if (res == 0 && fds[1] < 3) {
+        /* We always want the write end of the pipe to avoid fds 0, 1 and 2
+         * as our child may claim those for stdio connections. */
+        int write_fd = fds[1];
+        int fds_to_close[3] = {-1, -1, -1};
+        int fds_to_close_idx = 0;
+#ifdef F_DUPFD_CLOEXEC
+        fds_to_close[fds_to_close_idx++] = write_fd;
+        write_fd = fcntl(write_fd, F_DUPFD_CLOEXEC, 3);
+        if (write_fd < 0)  /* We don't support F_DUPFD_CLOEXEC / other error */
+#endif
+        {
+            /* Use dup a few times until we get a desirable fd. */
+            for (; fds_to_close_idx < 3; ++fds_to_close_idx) {
+                fds_to_close[fds_to_close_idx] = write_fd;
+                write_fd = dup(write_fd);
+                if (write_fd >= 3)
+                    break;
+                /* We may dup a few extra times if it returns an error but
+                 * that is okay.  Repeat calls should return the same error. */
+            }
+            if (write_fd < 0) res = write_fd;
+            if (res == 0) {
+                oldflags = fcntl(write_fd, F_GETFD, 0);
+                if (oldflags < 0) res = oldflags;
+                if (res == 0)
+                    res = fcntl(write_fd, F_SETFD, oldflags | FD_CLOEXEC);
+            }
+        }
+        saved_errno = errno;
+        /* Close fds we tried for the write end that were too low. */
+        for (fds_to_close_idx=0; fds_to_close_idx < 3; ++fds_to_close_idx) {
+            int temp_fd = fds_to_close[fds_to_close_idx];
+            while (temp_fd >= 0 && close(temp_fd) < 0 && errno == EINTR);
+        }
+        errno = saved_errno;  /* report dup or fcntl errors, not close. */
+        fds[1] = write_fd;
+    }  /* end if write fd was too small */
+
+    if (res != 0)
+        return PyErr_SetFromErrno(PyExc_OSError);
+    return Py_BuildValue("(ii)", fds[0], fds[1]);
+}
+
+/* module level code ********************************************************/
+
+#define MIN_PY_VERSION_WITH_PYIMPORT_ACQUIRELOCK 0x02060300
+#if (PY_VERSION_HEX < MIN_PY_VERSION_WITH_PYIMPORT_ACQUIRELOCK)
+static PyObject* imp_module;
+
+static void
+_PyImport_AcquireLock(void)
+{
+    PyObject *result;
+    result = PyObject_CallMethod(imp_module, "acquire_lock", NULL);
+    if (result == NULL) {
+        fprintf(stderr, "imp.acquire_lock() failed.\n");
+        return;
+    }
+    Py_DECREF(result);
+}
+
+static int
+_PyImport_ReleaseLock(void)
+{
+    PyObject *result;
+    result = PyObject_CallMethod(imp_module, "release_lock", NULL);
+    if (result == NULL) {
+        fprintf(stderr, "imp.release_lock() failed.\n");
+        return -1;
+    }
+    Py_DECREF(result);
+    return 0;
+}
+#endif /* Python <= 2.5 */
+
+
+PyDoc_STRVAR(module_doc,
+"A POSIX helper for the subprocess module.");
+
+
+static PyMethodDef module_methods[] = {
+    {"fork_exec", subprocess_fork_exec, METH_VARARGS, subprocess_fork_exec_doc},
+    {"cloexec_pipe", subprocess_cloexec_pipe, METH_NOARGS, subprocess_cloexec_pipe_doc},
+    {NULL, NULL}  /* sentinel */
+};
+
+
+PyMODINIT_FUNC
+init_posixsubprocess(void)
+{
+    PyObject *m;
+
+#ifdef _SC_OPEN_MAX
+    max_fd = sysconf(_SC_OPEN_MAX);
+    if (max_fd == -1)
+#endif
+        max_fd = 256;  /* Matches Lib/subprocess.py */
+
+#if (PY_VERSION_HEX < MIN_PY_VERSION_WITH_PYIMPORT_ACQUIRELOCK)
+    imp_module = PyImport_ImportModule("imp");
+    if (imp_module == NULL)
+        return;
+#endif
+
+    m = Py_InitModule3("_posixsubprocess", module_methods, module_doc);
+    if (m == NULL)
+        return;
+}