Re: [Valgrind-users] "noted but unhandled ioctl 0x2000747b with no size/direction hints" on Mac OS X

[Jeff J. <n3...@ma...>]

On Sep 17, 2009, at 3:42 PM, Sean McBride wrote:

> Hi all,
>
> Now that I've purged spaces from my paths :), valgrind has found  
> several
> bugs for me. yay!
>
> However, I'm now getting a new error/warning/thingie:
>
> ==9399== Warning: noted but unhandled ioctl 0x2000747b with no size/
> direction hints
> ==9399==    This could cause spurious value errors to appear.
> ==9399==    See README_MISSING_SYSCALL_OR_IOCTL for guidance on  
> writing
> a proper wrapper.
> ==9399== Warning: noted but unhandled ioctl 0x2000747a with no size/
> direction hints
> ==9399==    This could cause spurious value errors to appear.
>
> I've read the README_MISSING_SYSCALL_OR_IOCTL doc, but it gives the
> impression that I should be seeing a name instead of a hex number.
>
> I searched bugzilla for these magic numbers, but found nothing.
>
> How to proceed?  Is this a valgrind bug?
>

Not a valgrind bug per-se.

The short answer is that you are looking to "wrap" this ioctl on Mac  
OS X:

$ grep "'t', 123" */*.h
sys/ttycom.h:#define	TIOCSBRK	 _IO('t', 123)		/* set break bit */

That is decoded from 0x2000747b as follows:
	_IO(...)	0x20000000
	't'		0x74
	123		0x7b

Since no data is moving into or out of the kernel (that would use _IOR 
(...)
or _IOW(...) or _IOWR(...) wrapping, its just as easy to ignore the  
error
as anything else.

Ancient uglix lore ...

hth

73 de Jeff