ioctl request type should be unsigned long

[Marius van Voorden]

Summary: sb-unix:unix-ioctl uses a signed int as the ioctl request's type. This should be an unsigned long.
To reproduce: (sb-unix:unix-ioctl 0 (expt 2 31) nil)
Patch included.

The ioctl specification, insofar as it exists,[1] specifies the request type to be unsigned long.

Currently sbcl declares a (signed-byte 32), and uses the sb-alien C-type export of int. sb-alien uses a (signed-byte 32) for this, as ints in C are signed by default when no sign is declared.

This results in an error when ioctl commands larger than 2^31 are issued. For example, accessing SPI hardware registers on the Raspberry Pi requires commands larger than 2^31.[2]

It looks like at some point (15 years ago)[3] this argument type changed from signed-int to int, though as far as I understand removing the "signed" does not turn it into an unsigned integer.

Using unsigned-long as the type matches the ioctl specification, and works on my system. I don't know if this would break any currently existing programs, or if the cmd argument of unix-ioctl will get cast automatically in most cases.

(Without this patch, currently a workaround is possible by calling sb-unix:unix-ioctl with a negative number that then later gets interpreted as unsigned int. It's kinda ugly.[4])

[1] http://man7.org/linux/man-pages/man2/ioctl.2.html
[2] https://github.com/Shinmera/cl-spidev/blob/master/constants.lisp
[3] https://github.com/sbcl/sbcl/commit/0677c33068646b6ec33d5f622771673f3de38504#diff-e32cce0bfb6cd207741f69a9af4a57ce
[4] https://github.com/Shinmera/cl-spidev/commit/8b524a533d9cc52c57b9fae34c9b9d3f46385ef0

[Marius van Voorden (mqrius)]

Patch as attachment.

[Stas Boukarev (stassats)]

a) The patch doesn't apply.
b) The lisp declaration is still saying "32".
c) You shouldn't be using sb-unix:unix-ioctl at all, it's internal. Use sb-posix:ioctl, but it also uses int.

I fixed both sb-unix and sb-posix in 6a17b926afcfeea8781a328b0951aa552c96fb18