fileutils.c

#include "Python.h"
#include "osdefs.h"
#include <locale.h>

#ifdef MS_WINDOWS
#  include <malloc.h>
#  include <windows.h>
extern int winerror_to_errno(int);
#endif

#ifdef HAVE_LANGINFO_H
#include <langinfo.h>
#endif

#ifdef HAVE_SYS_IOCTL_H
#include <sys/ioctl.h>
#endif

#ifdef HAVE_FCNTL_H
#include <fcntl.h>
#endif /* HAVE_FCNTL_H */

#ifdef __APPLE__
extern wchar_t* _Py_DecodeUTF8_surrogateescape(const char *s, Py_ssize_t size);
#endif

#ifdef O_CLOEXEC
/* Does open() support the O_CLOEXEC flag? Possible values:

   -1: unknown
    0: open() ignores O_CLOEXEC flag, ex: Linux kernel older than 2.6.23
    1: open() supports O_CLOEXEC flag, close-on-exec is set

   The flag is used by _Py_open(), _Py_open_noraise(), io.FileIO
   and os.open(). */
int _Py_open_cloexec_works = -1;
#endif

PyObject *
_Py_device_encoding(int fd)
{
#if defined(MS_WINDOWS)
    UINT cp;
#endif
    int valid;
    _Py_BEGIN_SUPPRESS_IPH
    valid = _PyVerify_fd(fd) && isatty(fd);
    _Py_END_SUPPRESS_IPH
    if (!valid)
        Py_RETURN_NONE;

#if defined(MS_WINDOWS)
    if (fd == 0)
        cp = GetConsoleCP();
    else if (fd == 1 || fd == 2)
        cp = GetConsoleOutputCP();
    else
        cp = 0;
    /* GetConsoleCP() and GetConsoleOutputCP() return 0 if the application
       has no console */
    if (cp != 0)
        return PyUnicode_FromFormat("cp%u", (unsigned int)cp);
#elif defined(CODESET)
    {
        char *codeset = nl_langinfo(CODESET);
        if (codeset != NULL && codeset[0] != 0)
            return PyUnicode_FromString(codeset);
    }
#endif
    Py_RETURN_NONE;
}

#if !defined(__APPLE__) && !defined(MS_WINDOWS)
extern int _Py_normalize_encoding(const char *, char *, size_t);

/* Workaround FreeBSD and OpenIndiana locale encoding issue with the C locale.
   On these operating systems, nl_langinfo(CODESET) announces an alias of the
   ASCII encoding, whereas mbstowcs() and wcstombs() functions use the
   ISO-8859-1 encoding. The problem is that os.fsencode() and os.fsdecode() use
   locale.getpreferredencoding() codec. For example, if command line arguments
   are decoded by mbstowcs() and encoded back by os.fsencode(), we get a
   UnicodeEncodeError instead of retrieving the original byte string.

   The workaround is enabled if setlocale(LC_CTYPE, NULL) returns "C",
   nl_langinfo(CODESET) announces "ascii" (or an alias to ASCII), and at least
   one byte in range 0x80-0xff can be decoded from the locale encoding. The
   workaround is also enabled on error, for example if getting the locale
   failed.

   Values of force_ascii:

       1: the workaround is used: Py_EncodeLocale() uses
          encode_ascii_surrogateescape() and Py_DecodeLocale() uses
          decode_ascii_surrogateescape()
       0: the workaround is not used: Py_EncodeLocale() uses wcstombs() and
          Py_DecodeLocale() uses mbstowcs()
      -1: unknown, need to call check_force_ascii() to get the value
*/
static int force_ascii = -1;

static int
check_force_ascii(void)
{
    char *loc;
#if defined(HAVE_LANGINFO_H) && defined(CODESET)
    char *codeset, **alias;
    char encoding[100];
    int is_ascii;
    unsigned int i;
    char* ascii_aliases[] = {
        "ascii",
        "646",
        "ansi-x3.4-1968",
        "ansi-x3-4-1968",
        "ansi-x3.4-1986",
        "cp367",
        "csascii",
        "ibm367",
        "iso646-us",
        "iso-646.irv-1991",
        "iso-ir-6",
        "us",
        "us-ascii",
        NULL
    };
#endif

    loc = setlocale(LC_CTYPE, NULL);
    if (loc == NULL)
        goto error;
    if (strcmp(loc, "C") != 0) {
        /* the LC_CTYPE locale is different than C */
        return 0;
    }

#if defined(HAVE_LANGINFO_H) && defined(CODESET)
    codeset = nl_langinfo(CODESET);
    if (!codeset || codeset[0] == '\0') {
        /* CODESET is not set or empty */
        goto error;
    }
    if (!_Py_normalize_encoding(codeset, encoding, sizeof(encoding)))
        goto error;

    is_ascii = 0;
    for (alias=ascii_aliases; *alias != NULL; alias++) {
        if (strcmp(encoding, *alias) == 0) {
            is_ascii = 1;
            break;
        }
    }
    if (!is_ascii) {
        /* nl_langinfo(CODESET) is not "ascii" or an alias of ASCII */
        return 0;
    }

    for (i=0x80; i<0xff; i++) {
        unsigned char ch;
        wchar_t wch;
        size_t res;

        ch = (unsigned char)i;
        res = mbstowcs(&wch, (char*)&ch, 1);
        if (res != (size_t)-1) {
            /* decoding a non-ASCII character from the locale encoding succeed:
               the locale encoding is not ASCII, force ASCII */
            return 1;
        }
    }
    /* None of the bytes in the range 0x80-0xff can be decoded from the locale
       encoding: the locale encoding is really ASCII */
    return 0;
#else
    /* nl_langinfo(CODESET) is not available: always force ASCII */
    return 1;
#endif

error:
    /* if an error occured, force the ASCII encoding */
    return 1;
}

static char*
encode_ascii_surrogateescape(const wchar_t *text, size_t *error_pos)
{
    char *result = NULL, *out;
    size_t len, i;
    wchar_t ch;

    if (error_pos != NULL)
        *error_pos = (size_t)-1;

    len = wcslen(text);

    result = PyMem_Malloc(len + 1);  /* +1 for NUL byte */
    if (result == NULL)
        return NULL;

    out = result;
    for (i=0; i<len; i++) {
        ch = text[i];

        if (ch <= 0x7f) {
            /* ASCII character */
            *out++ = (char)ch;
        }
        else if (0xdc80 <= ch && ch <= 0xdcff) {
            /* UTF-8b surrogate */
            *out++ = (char)(ch - 0xdc00);
        }
        else {
            if (error_pos != NULL)
                *error_pos = i;
            PyMem_Free(result);
            return NULL;
        }
    }
    *out = '\0';
    return result;
}
#endif   /* !defined(__APPLE__) && !defined(MS_WINDOWS) */

#if !defined(__APPLE__) && (!defined(MS_WINDOWS) || !defined(HAVE_MBRTOWC))
static wchar_t*
decode_ascii_surrogateescape(const char *arg, size_t *size)
{
    wchar_t *res;
    unsigned char *in;
    wchar_t *out;
    size_t argsize = strlen(arg) + 1;

    if (argsize > PY_SSIZE_T_MAX/sizeof(wchar_t))
        return NULL;
    res = PyMem_RawMalloc(argsize*sizeof(wchar_t));
    if (!res)
        return NULL;

    in = (unsigned char*)arg;
    out = res;
    while(*in)
        if(*in < 128)
            *out++ = *in++;
        else
            *out++ = 0xdc00 + *in++;
    *out = 0;
    if (size != NULL)
        *size = out - res;
    return res;
}
#endif


/* Decode a byte string from the locale encoding with the
   surrogateescape error handler: undecodable bytes are decoded as characters
   in range U+DC80..U+DCFF. If a byte sequence can be decoded as a surrogate
   character, escape the bytes using the surrogateescape error handler instead
   of decoding them.

   Return a pointer to a newly allocated wide character string, use
   PyMem_RawFree() to free the memory. If size is not NULL, write the number of
   wide characters excluding the null character into *size

   Return NULL on decoding error or memory allocation error. If *size* is not
   NULL, *size is set to (size_t)-1 on memory error or set to (size_t)-2 on
   decoding error.

   Decoding errors should never happen, unless there is a bug in the C
   library.

   Use the Py_EncodeLocale() function to encode the character string back to a
   byte string. */
wchar_t*
Py_DecodeLocale(const char* arg, size_t *size)
{
#ifdef __APPLE__
    wchar_t *wstr;
    wstr = _Py_DecodeUTF8_surrogateescape(arg, strlen(arg));
    if (size != NULL) {
        if (wstr != NULL)
            *size = wcslen(wstr);
        else
            *size = (size_t)-1;
    }
    return wstr;
#else
    wchar_t *res;
    size_t argsize;
    size_t count;
#ifdef HAVE_MBRTOWC
    unsigned char *in;
    wchar_t *out;
    mbstate_t mbs;
#endif

#ifndef MS_WINDOWS
    if (force_ascii == -1)
        force_ascii = check_force_ascii();

    if (force_ascii) {
        /* force ASCII encoding to workaround mbstowcs() issue */
        res = decode_ascii_surrogateescape(arg, size);
        if (res == NULL)
            goto oom;
        return res;
    }
#endif

#ifdef HAVE_BROKEN_MBSTOWCS
    /* Some platforms have a broken implementation of
     * mbstowcs which does not count the characters that
     * would result from conversion.  Use an upper bound.
     */
    argsize = strlen(arg);
#else
    argsize = mbstowcs(NULL, arg, 0);
#endif
    if (argsize != (size_t)-1) {
        if (argsize == PY_SSIZE_T_MAX)
            goto oom;
        argsize += 1;
        if (argsize > PY_SSIZE_T_MAX/sizeof(wchar_t))
            goto oom;
        res = (wchar_t *)PyMem_RawMalloc(argsize*sizeof(wchar_t));
        if (!res)
            goto oom;
        count = mbstowcs(res, arg, argsize);
        if (count != (size_t)-1) {
            wchar_t *tmp;
            /* Only use the result if it contains no
               surrogate characters. */
            for (tmp = res; *tmp != 0 &&
                         !Py_UNICODE_IS_SURROGATE(*tmp); tmp++)
                ;
            if (*tmp == 0) {
                if (size != NULL)
                    *size = count;
                return res;
            }
        }
        PyMem_RawFree(res);
    }
    /* Conversion failed. Fall back to escaping with surrogateescape. */
#ifdef HAVE_MBRTOWC
    /* Try conversion with mbrtwoc (C99), and escape non-decodable bytes. */

    /* Overallocate; as multi-byte characters are in the argument, the
       actual output could use less memory. */
    argsize = strlen(arg) + 1;
    if (argsize > PY_SSIZE_T_MAX/sizeof(wchar_t))
        goto oom;
    res = (wchar_t*)PyMem_RawMalloc(argsize*sizeof(wchar_t));
    if (!res)
        goto oom;
    in = (unsigned char*)arg;
    out = res;
    memset(&mbs, 0, sizeof mbs);
    while (argsize) {
        size_t converted = mbrtowc(out, (char*)in, argsize, &mbs);
        if (converted == 0)
            /* Reached end of string; null char stored. */
            break;
        if (converted == (size_t)-2) {
            /* Incomplete character. This should never happen,
               since we provide everything that we have -
               unless there is a bug in the C library, or I
               misunderstood how mbrtowc works. */
            PyMem_RawFree(res);
            if (size != NULL)
                *size = (size_t)-2;
            return NULL;
        }
        if (converted == (size_t)-1) {
            /* Conversion error. Escape as UTF-8b, and start over
               in the initial shift state. */
            *out++ = 0xdc00 + *in++;
            argsize--;
            memset(&mbs, 0, sizeof mbs);
            continue;
        }
        if (Py_UNICODE_IS_SURROGATE(*out)) {
            /* Surrogate character.  Escape the original
               byte sequence with surrogateescape. */
            argsize -= converted;
            while (converted--)
                *out++ = 0xdc00 + *in++;
            continue;
        }
        /* successfully converted some bytes */
        in += converted;
        argsize -= converted;
        out++;
    }
    if (size != NULL)
        *size = out - res;
#else   /* HAVE_MBRTOWC */
    /* Cannot use C locale for escaping; manually escape as if charset
       is ASCII (i.e. escape all bytes > 128. This will still roundtrip
       correctly in the locale's charset, which must be an ASCII superset. */
    res = decode_ascii_surrogateescape(arg, size);
    if (res == NULL)
        goto oom;
#endif   /* HAVE_MBRTOWC */
    return res;
oom:
    if (size != NULL)
        *size = (size_t)-1;
    return NULL;
#endif   /* __APPLE__ */
}

/* Encode a wide character string to the locale encoding with the
   surrogateescape error handler: surrogate characters in the range
   U+DC80..U+DCFF are converted to bytes 0x80..0xFF.

   Return a pointer to a newly allocated byte string, use PyMem_Free() to free
   the memory. Return NULL on encoding or memory allocation error.

   If error_pos is not NULL, *error_pos is set to the index of the invalid
   character on encoding error, or set to (size_t)-1 otherwise.

   Use the Py_DecodeLocale() function to decode the bytes string back to a wide
   character string. */
char*
Py_EncodeLocale(const wchar_t *text, size_t *error_pos)
{
#ifdef __APPLE__
    Py_ssize_t len;
    PyObject *unicode, *bytes = NULL;
    char *cpath;

    unicode = PyUnicode_FromWideChar(text, wcslen(text));
    if (unicode == NULL)
        return NULL;

    bytes = _PyUnicode_AsUTF8String(unicode, "surrogateescape");
    Py_DECREF(unicode);
    if (bytes == NULL) {
        PyErr_Clear();
        if (error_pos != NULL)
            *error_pos = (size_t)-1;
        return NULL;
    }

    len = PyBytes_GET_SIZE(bytes);
    cpath = PyMem_Malloc(len+1);
    if (cpath == NULL) {
        PyErr_Clear();
        Py_DECREF(bytes);
        if (error_pos != NULL)
            *error_pos = (size_t)-1;
        return NULL;
    }
    memcpy(cpath, PyBytes_AsString(bytes), len + 1);
    Py_DECREF(bytes);
    return cpath;
#else   /* __APPLE__ */
    const size_t len = wcslen(text);
    char *result = NULL, *bytes = NULL;
    size_t i, size, converted;
    wchar_t c, buf[2];

#ifndef MS_WINDOWS
    if (force_ascii == -1)
        force_ascii = check_force_ascii();

    if (force_ascii)
        return encode_ascii_surrogateescape(text, error_pos);
#endif

    /* The function works in two steps:
       1. compute the length of the output buffer in bytes (size)
       2. outputs the bytes */
    size = 0;
    buf[1] = 0;
    while (1) {
        for (i=0; i < len; i++) {
            c = text[i];
            if (c >= 0xdc80 && c <= 0xdcff) {
                /* UTF-8b surrogate */
                if (bytes != NULL) {
                    *bytes++ = c - 0xdc00;
                    size--;
                }
                else
                    size++;
                continue;
            }
            else {
                buf[0] = c;
                if (bytes != NULL)
                    converted = wcstombs(bytes, buf, size);
                else
                    converted = wcstombs(NULL, buf, 0);
                if (converted == (size_t)-1) {
                    if (result != NULL)
                        PyMem_Free(result);
                    if (error_pos != NULL)
                        *error_pos = i;
                    return NULL;
                }
                if (bytes != NULL) {
                    bytes += converted;
                    size -= converted;
                }
                else
                    size += converted;
            }
        }
        if (result != NULL) {
            *bytes = '\0';
            break;
        }

        size += 1; /* nul byte at the end */
        result = PyMem_Malloc(size);
        if (result == NULL) {
            if (error_pos != NULL)
                *error_pos = (size_t)-1;
            return NULL;
        }
        bytes = result;
    }
    return result;
#endif   /* __APPLE__ */
}


#ifdef MS_WINDOWS
static __int64 secs_between_epochs = 11644473600; /* Seconds between 1.1.1601 and 1.1.1970 */

static void
FILE_TIME_to_time_t_nsec(FILETIME *in_ptr, time_t *time_out, int* nsec_out)
{
    /* XXX endianness. Shouldn't matter, as all Windows implementations are little-endian */
    /* Cannot simply cast and dereference in_ptr,
       since it might not be aligned properly */
    __int64 in;
    memcpy(&in, in_ptr, sizeof(in));
    *nsec_out = (int)(in % 10000000) * 100; /* FILETIME is in units of 100 nsec. */
    *time_out = Py_SAFE_DOWNCAST((in / 10000000) - secs_between_epochs, __int64, time_t);
}

void
_Py_time_t_to_FILE_TIME(time_t time_in, int nsec_in, FILETIME *out_ptr)
{
    /* XXX endianness */
    __int64 out;
    out = time_in + secs_between_epochs;
    out = out * 10000000 + nsec_in / 100;
    memcpy(out_ptr, &out, sizeof(out));
}

/* Below, we *know* that ugo+r is 0444 */
#if _S_IREAD != 0400
#error Unsupported C library
#endif
static int
attributes_to_mode(DWORD attr)
{
    int m = 0;
    if (attr & FILE_ATTRIBUTE_DIRECTORY)
        m |= _S_IFDIR | 0111; /* IFEXEC for user,group,other */
    else
        m |= _S_IFREG;
    if (attr & FILE_ATTRIBUTE_READONLY)
        m |= 0444;
    else
        m |= 0666;
    return m;
}

void
_Py_attribute_data_to_stat(BY_HANDLE_FILE_INFORMATION *info, ULONG reparse_tag,
                           struct _Py_stat_struct *result)
{
    memset(result, 0, sizeof(*result));
    result->st_mode = attributes_to_mode(info->dwFileAttributes);
    result->st_size = (((__int64)info->nFileSizeHigh)<<32) + info->nFileSizeLow;
    result->st_dev = info->dwVolumeSerialNumber;
    result->st_rdev = result->st_dev;
    FILE_TIME_to_time_t_nsec(&info->ftCreationTime, &result->st_ctime, &result->st_ctime_nsec);
    FILE_TIME_to_time_t_nsec(&info->ftLastWriteTime, &result->st_mtime, &result->st_mtime_nsec);
    FILE_TIME_to_time_t_nsec(&info->ftLastAccessTime, &result->st_atime, &result->st_atime_nsec);
    result->st_nlink = info->nNumberOfLinks;
    result->st_ino = (((__int64)info->nFileIndexHigh)<<32) + info->nFileIndexLow;
    if (reparse_tag == IO_REPARSE_TAG_SYMLINK) {
        /* first clear the S_IFMT bits */
        result->st_mode ^= (result->st_mode & S_IFMT);
        /* now set the bits that make this a symlink */
        result->st_mode |= S_IFLNK;
    }
    result->st_file_attributes = info->dwFileAttributes;
}
#endif

/* Return information about a file.

   On POSIX, use fstat().

   On Windows, use GetFileType() and GetFileInformationByHandle() which support
   files larger than 2 GB.  fstat() may fail with EOVERFLOW on files larger
   than 2 GB because the file size type is a signed 32-bit integer: see issue
   #23152.

   On Windows, set the last Windows error and return nonzero on error. On
   POSIX, set errno and return nonzero on error. Fill status and return 0 on
   success. */
int
_Py_fstat_noraise(int fd, struct _Py_stat_struct *status)
{
#ifdef MS_WINDOWS
    BY_HANDLE_FILE_INFORMATION info;
    HANDLE h;
    int type;

    if (!_PyVerify_fd(fd))
        h = INVALID_HANDLE_VALUE;
    else {
        _Py_BEGIN_SUPPRESS_IPH
        h = (HANDLE)_get_osfhandle(fd);
        _Py_END_SUPPRESS_IPH
    }

    if (h == INVALID_HANDLE_VALUE) {
        /* errno is already set by _get_osfhandle, but we also set
           the Win32 error for callers who expect that */
        SetLastError(ERROR_INVALID_HANDLE);
        return -1;
    }
    memset(status, 0, sizeof(*status));

    type = GetFileType(h);
    if (type == FILE_TYPE_UNKNOWN) {
        DWORD error = GetLastError();
        if (error != 0) {
            errno = winerror_to_errno(error);
            return -1;
        }
        /* else: valid but unknown file */
    }

    if (type != FILE_TYPE_DISK) {
        if (type == FILE_TYPE_CHAR)
            status->st_mode = _S_IFCHR;
        else if (type == FILE_TYPE_PIPE)
            status->st_mode = _S_IFIFO;
        return 0;
    }

    if (!GetFileInformationByHandle(h, &info)) {
        /* The Win32 error is already set, but we also set errno for
           callers who expect it */
        errno = winerror_to_errno(GetLastError());
        return -1;
    }

    _Py_attribute_data_to_stat(&info, 0, status);
    /* specific to fstat() */
    status->st_ino = (((__int64)info.nFileIndexHigh)<<32) + info.nFileIndexLow;
    return 0;
#else
    return fstat(fd, status);
#endif
}

/* Return information about a file.

   On POSIX, use fstat().

   On Windows, use GetFileType() and GetFileInformationByHandle() which support
   files larger than 2 GB.  fstat() may fail with EOVERFLOW on files larger
   than 2 GB because the file size type is a signed 32-bit integer: see issue
   #23152.

   Raise an exception and return -1 on error. On Windows, set the last Windows
   error on error. On POSIX, set errno on error. Fill status and return 0 on
   success.

   Release the GIL to call GetFileType() and GetFileInformationByHandle(), or
   to call fstat(). The caller must hold the GIL. */
int
_Py_fstat(int fd, struct _Py_stat_struct *status)
{
    int res;

#ifdef WITH_THREAD
    assert(PyGILState_Check());
#endif

    Py_BEGIN_ALLOW_THREADS
    res = _Py_fstat_noraise(fd, status);
    Py_END_ALLOW_THREADS

    if (res != 0) {
#ifdef MS_WINDOWS
        PyErr_SetFromWindowsErr(0);
#else
        PyErr_SetFromErrno(PyExc_OSError);
#endif
        return -1;
    }
    return 0;
}

/* Call _wstat() on Windows, or encode the path to the filesystem encoding and
   call stat() otherwise. Only fill st_mode attribute on Windows.

   Return 0 on success, -1 on _wstat() / stat() error, -2 if an exception was
   raised. */

int
_Py_stat(PyObject *path, struct stat *statbuf)
{
#ifdef MS_WINDOWS
    int err;
    struct _stat wstatbuf;
    wchar_t *wpath;

    wpath = PyUnicode_AsUnicode(path);
    if (wpath == NULL)
        return -2;
    err = _wstat(wpath, &wstatbuf);
    if (!err)
        statbuf->st_mode = wstatbuf.st_mode;
    return err;
#else
    int ret;
    PyObject *bytes = PyUnicode_EncodeFSDefault(path);
    if (bytes == NULL)
        return -2;
    ret = stat(PyBytes_AS_STRING(bytes), statbuf);
    Py_DECREF(bytes);
    return ret;
#endif
}


static int
get_inheritable(int fd, int raise)
{
#ifdef MS_WINDOWS
    HANDLE handle;
    DWORD flags;

    if (!_PyVerify_fd(fd)) {
        if (raise)
            PyErr_SetFromErrno(PyExc_OSError);
        return -1;
    }

    _Py_BEGIN_SUPPRESS_IPH
    handle = (HANDLE)_get_osfhandle(fd);
    _Py_END_SUPPRESS_IPH
    if (handle == INVALID_HANDLE_VALUE) {
        if (raise)
            PyErr_SetFromErrno(PyExc_OSError);
        return -1;
    }

    if (!GetHandleInformation(handle, &flags)) {
        if (raise)
            PyErr_SetFromWindowsErr(0);
        return -1;
    }

    return (flags & HANDLE_FLAG_INHERIT);
#else
    int flags;

    flags = fcntl(fd, F_GETFD, 0);
    if (flags == -1) {
        if (raise)
            PyErr_SetFromErrno(PyExc_OSError);
        return -1;
    }
    return !(flags & FD_CLOEXEC);
#endif
}

/* Get the inheritable flag of the specified file descriptor.
   Return 1 if the file descriptor can be inherited, 0 if it cannot,
   raise an exception and return -1 on error. */
int
_Py_get_inheritable(int fd)
{
    return get_inheritable(fd, 1);
}

static int
set_inheritable(int fd, int inheritable, int raise, int *atomic_flag_works)
{
#ifdef MS_WINDOWS
    HANDLE handle;
    DWORD flags;
#else
#if defined(HAVE_SYS_IOCTL_H) && defined(FIOCLEX) && defined(FIONCLEX)
    static int ioctl_works = -1;
    int request;
    int err;
#endif
    int flags, new_flags;
    int res;
#endif

    /* atomic_flag_works can only be used to make the file descriptor
       non-inheritable */
    assert(!(atomic_flag_works != NULL && inheritable));

    if (atomic_flag_works != NULL && !inheritable) {
        if (*atomic_flag_works == -1) {
            int isInheritable = get_inheritable(fd, raise);
            if (isInheritable == -1)
                return -1;
            *atomic_flag_works = !isInheritable;
        }

        if (*atomic_flag_works)
            return 0;
    }

#ifdef MS_WINDOWS
    if (!_PyVerify_fd(fd)) {
        if (raise)
            PyErr_SetFromErrno(PyExc_OSError);
        return -1;
    }

    _Py_BEGIN_SUPPRESS_IPH
    handle = (HANDLE)_get_osfhandle(fd);
    _Py_END_SUPPRESS_IPH
    if (handle == INVALID_HANDLE_VALUE) {
        if (raise)
            PyErr_SetFromErrno(PyExc_OSError);
        return -1;
    }

    if (inheritable)
        flags = HANDLE_FLAG_INHERIT;
    else
        flags = 0;
    if (!SetHandleInformation(handle, HANDLE_FLAG_INHERIT, flags)) {
        if (raise)
            PyErr_SetFromWindowsErr(0);
        return -1;
    }
    return 0;

#else

#if defined(HAVE_SYS_IOCTL_H) && defined(FIOCLEX) && defined(FIONCLEX)
    if (ioctl_works != 0) {
        /* fast-path: ioctl() only requires one syscall */
        if (inheritable)
            request = FIONCLEX;
        else
            request = FIOCLEX;
        err = ioctl(fd, request, NULL);
        if (!err) {
            ioctl_works = 1;
            return 0;
        }

        if (errno != ENOTTY) {
            if (raise)
                PyErr_SetFromErrno(PyExc_OSError);
            return -1;
        }
        else {
            /* Issue #22258: Here, ENOTTY means "Inappropriate ioctl for
               device". The ioctl is declared but not supported by the kernel.
               Remember that ioctl() doesn't work. It is the case on
               Illumos-based OS for example. */
            ioctl_works = 0;
        }
        /* fallback to fcntl() if ioctl() does not work */
    }
#endif

    /* slow-path: fcntl() requires two syscalls */
    flags = fcntl(fd, F_GETFD);
    if (flags < 0) {
        if (raise)
            PyErr_SetFromErrno(PyExc_OSError);
        return -1;
    }

    if (inheritable) {
        new_flags = flags & ~FD_CLOEXEC;
    }
    else {
        new_flags = flags | FD_CLOEXEC;
    }

    if (new_flags == flags) {
        /* FD_CLOEXEC flag already set/cleared: nothing to do */
        return 0;
    }

    res = fcntl(fd, F_SETFD, flags);
    if (res < 0) {
        if (raise)
            PyErr_SetFromErrno(PyExc_OSError);
        return -1;
    }
    return 0;
#endif
}

/* Make the file descriptor non-inheritable.
   Return 0 on success, set errno and return -1 on error. */
static int
make_non_inheritable(int fd)
{
    return set_inheritable(fd, 0, 0, NULL);
}

/* Set the inheritable flag of the specified file descriptor.
   On success: return 0, on error: raise an exception if raise is nonzero
   and return -1.

   If atomic_flag_works is not NULL:

    * if *atomic_flag_works==-1, check if the inheritable is set on the file
      descriptor: if yes, set *atomic_flag_works to 1, otherwise set to 0 and
      set the inheritable flag
    * if *atomic_flag_works==1: do nothing
    * if *atomic_flag_works==0: set inheritable flag to False

   Set atomic_flag_works to NULL if no atomic flag was used to create the
   file descriptor.

   atomic_flag_works can only be used to make a file descriptor
   non-inheritable: atomic_flag_works must be NULL if inheritable=1. */
int
_Py_set_inheritable(int fd, int inheritable, int *atomic_flag_works)
{
    return set_inheritable(fd, inheritable, 1, atomic_flag_works);
}

static int
_Py_open_impl(const char *pathname, int flags, int gil_held)
{
    int fd;
    int async_err = 0;
#ifndef MS_WINDOWS
    int *atomic_flag_works;
#endif

#ifdef MS_WINDOWS
    flags |= O_NOINHERIT;
#elif defined(O_CLOEXEC)
    atomic_flag_works = &_Py_open_cloexec_works;
    flags |= O_CLOEXEC;
#else
    atomic_flag_works = NULL;
#endif

    if (gil_held) {
        do {
            Py_BEGIN_ALLOW_THREADS
            fd = open(pathname, flags);
            Py_END_ALLOW_THREADS
        } while (fd < 0
                 && errno == EINTR && !(async_err = PyErr_CheckSignals()));
        if (async_err)
            return -1;
        if (fd < 0) {
            PyErr_SetFromErrnoWithFilename(PyExc_OSError, pathname);
            return -1;
        }
    }
    else {
        fd = open(pathname, flags);
        if (fd < 0)
            return -1;
    }

#ifndef MS_WINDOWS
    if (set_inheritable(fd, 0, gil_held, atomic_flag_works) < 0) {
        close(fd);
        return -1;
    }
#endif

    return fd;
}

/* Open a file with the specified flags (wrapper to open() function).
   Return a file descriptor on success. Raise an exception and return -1 on
   error.

   The file descriptor is created non-inheritable.

   When interrupted by a signal (open() fails with EINTR), retry the syscall,
   except if the Python signal handler raises an exception.

   Release the GIL to call open(). The caller must hold the GIL. */
int
_Py_open(const char *pathname, int flags)
{