diff options
Diffstat (limited to 'Modules/fcntlmodule.c')
| -rw-r--r-- | Modules/fcntlmodule.c | 19 |
1 files changed, 14 insertions, 5 deletions
diff --git a/Modules/fcntlmodule.c b/Modules/fcntlmodule.c index 1539f21ff8..6447e5686b 100644 --- a/Modules/fcntlmodule.c +++ b/Modules/fcntlmodule.c @@ -97,11 +97,20 @@ fcntl_ioctl(PyObject *self, PyObject *args) { #define IOCTL_BUFSZ 1024 int fd; - /* In PyArg_ParseTuple below, use the unsigned int 'I' format for - the signed int 'code' variable, because Python turns 0x8000000 - into a large positive number (PyLong, or PyInt on 64-bit - platforms,) whereas C expects it to be a negative int */ - int code; + /* In PyArg_ParseTuple below, we use the unsigned non-checked 'I' + format for the 'code' parameter because Python turns 0x8000000 + into either a large positive number (PyLong or PyInt on 64-bit + platforms) or a negative number on others (32-bit PyInt) + whereas the system expects it to be a 32bit bit field value + regardless of it being passed as an int or unsigned long on + various platforms. See the termios.TIOCSWINSZ constant across + platforms for an example of thise. + + If any of the 64bit platforms ever decide to use more than 32bits + in their unsigned long ioctl codes this will break and need + special casing based on the platform being built on. + */ + unsigned int code; int arg; int ret; char *str; |