On 13.08.2019 20:22, Jaromir Dolecek wrote: > I think the rationale was to make it possible to use for integer values and > operations without cast. And make it clear it can hold arbitrary value, not > necessarily pointer. Unfortunately intptr_t has different size in 32 vs 64 > bit same as void *, which I didnt consider. > > Using (void *) would be bad IMO. If we want to change this, please follow the > mac OS and use explicit integer 64bit types instead. This would of course > change ABI so needs versioning. >
Darwin uses void* for udata.
The kevent structure is defined as:
struct kevent {
uintptr_t ident; /* identifier for this event */
short filter; /* filter for event */
u_short flags; /* action flags for kqueue */
u_int fflags; /* filter flag value */
intptr_t data; /* filter data value */
void *udata; /* opaque user data identifier */
};
https://developer.apple.com/library/archive/documentation/System/Conceptual/ManPages_iPhoneOS/man2/kqueue.2.html
Imho int64_t make things actually worse.
1. Every pointer than can exceed 32bit intptr_t can just be allocated
on a heap and we should pass a pointer to it.
2. int64 does not resolve any C++ issues with strict types.
3. ABI brekage
void* does not prevent storing inside it numbers.
void* (or char*, int*,...) is a typical userdata argument. It can be
found in this form in other places such as set_panel_userptr(3),
FTSENT.fts_pointer in fts(3) or tss_set(3).
> Jaromir
>
>
>
>> Le 12 août 2019 à 14:51, Valery Ushakov <u...@stderr.spb.ru> a écrit :
>>
>>> On Mon, Aug 12, 2019 at 03:43:56 +0000, m...@netbsd.org wrote:
>>>
>>> So, this is when we changed to intptr_t. We also went through a
>>> "int64_t udata" revision at some point, later.
>>>
>>> Module Name: syssrc
>>> Committed By: jdolecek
>>> Date: Wed Oct 2 19:09:37 UTC 2002
>>>
>>> Modified Files:
>>> syssrc/sys/sys [kqueue]: event.h
>>>
>>> Log Message:
>>> make 'udata' field of struct kevent intptr_t (was 'void *')
>> [...]
>>> jdolecek, do you remember why you wanted to switch?
>>
>> Could it be related to 64-bit kernel vs. 32-bit userland (one of the
>> mips ABIs?)
>>
>> -uwe
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