* [Bug c/26372] opposite of may_alias attribute
2006-02-19 21:29 [Bug c/26372] New: opposite of may_alias attribute acahalan at gmail dot com
@ 2006-02-19 21:31 ` pinskia at gcc dot gnu dot org
2006-02-19 21:40 ` acahalan at gmail dot com
` (5 subsequent siblings)
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From: pinskia at gcc dot gnu dot org @ 2006-02-19 21:31 UTC (permalink / raw)
To: gcc-bugs
------- Comment #1 from pinskia at gcc dot gnu dot org 2006-02-19 21:31 -------
__restrict it is called.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26372
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* [Bug c/26372] opposite of may_alias attribute
2006-02-19 21:29 [Bug c/26372] New: opposite of may_alias attribute acahalan at gmail dot com
2006-02-19 21:31 ` [Bug c/26372] " pinskia at gcc dot gnu dot org
@ 2006-02-19 21:40 ` acahalan at gmail dot com
2006-02-20 2:04 ` pinskia at gcc dot gnu dot org
` (4 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: acahalan at gmail dot com @ 2006-02-19 21:40 UTC (permalink / raw)
To: gcc-bugs
------- Comment #2 from acahalan at gmail dot com 2006-02-19 21:40 -------
No, __restrict is too strong. It also, last I heard, couldn't be applied to a
type.
(if restrict was right, then using it on an int would be redundant)
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26372
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* [Bug c/26372] opposite of may_alias attribute
2006-02-19 21:29 [Bug c/26372] New: opposite of may_alias attribute acahalan at gmail dot com
2006-02-19 21:31 ` [Bug c/26372] " pinskia at gcc dot gnu dot org
2006-02-19 21:40 ` acahalan at gmail dot com
@ 2006-02-20 2:04 ` pinskia at gcc dot gnu dot org
2006-02-20 3:29 ` acahalan at gmail dot com
` (3 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2006-02-20 2:04 UTC (permalink / raw)
To: gcc-bugs
------- Comment #3 from pinskia at gcc dot gnu dot org 2006-02-20 02:04 -------
Can you give an example of where this is useful and why not instead improve GCC
for your code gen issues?
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26372
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* [Bug c/26372] opposite of may_alias attribute
2006-02-19 21:29 [Bug c/26372] New: opposite of may_alias attribute acahalan at gmail dot com
` (2 preceding siblings ...)
2006-02-20 2:04 ` pinskia at gcc dot gnu dot org
@ 2006-02-20 3:29 ` acahalan at gmail dot com
2006-02-21 10:18 ` rguenth at gcc dot gnu dot org
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From: acahalan at gmail dot com @ 2006-02-20 3:29 UTC (permalink / raw)
To: gcc-bugs
------- Comment #4 from acahalan at gmail dot com 2006-02-20 03:29 -------
There have been times when I could not prove to myself that __restrict would be
safe (it may have been), yet I knew that the char pointer would not alias with
non-char pointers.
(sorry to not have a nice chunk of code handy -- I just discovered where to
report gcc bugs and missing features, so I had a backlog of things that have
bothered me over the years)
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26372
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* [Bug c/26372] opposite of may_alias attribute
2006-02-19 21:29 [Bug c/26372] New: opposite of may_alias attribute acahalan at gmail dot com
` (3 preceding siblings ...)
2006-02-20 3:29 ` acahalan at gmail dot com
@ 2006-02-21 10:18 ` rguenth at gcc dot gnu dot org
2006-02-22 3:28 ` acahalan at gmail dot com
2006-07-19 3:48 ` pinskia at gcc dot gnu dot org
6 siblings, 0 replies; 8+ messages in thread
From: rguenth at gcc dot gnu dot org @ 2006-02-21 10:18 UTC (permalink / raw)
To: gcc-bugs
------- Comment #5 from rguenth at gcc dot gnu dot org 2006-02-21 10:17 -------
This needs more explanation. char pointers are special with and without
strict-aliasing.
--
rguenth at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |WAITING
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26372
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* [Bug c/26372] opposite of may_alias attribute
2006-02-19 21:29 [Bug c/26372] New: opposite of may_alias attribute acahalan at gmail dot com
` (4 preceding siblings ...)
2006-02-21 10:18 ` rguenth at gcc dot gnu dot org
@ 2006-02-22 3:28 ` acahalan at gmail dot com
2006-07-19 3:48 ` pinskia at gcc dot gnu dot org
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From: acahalan at gmail dot com @ 2006-02-22 3:28 UTC (permalink / raw)
To: gcc-bugs
------- Comment #6 from acahalan at gmail dot com 2006-02-22 03:28 -------
Yes, char pointers are special. I'd like a non-special char pointer.
I often know that a char pointer will never alias non-char data, but can not
prove that it obeys all the complicated rules for __restrict.
For non-char pointers the attribute would be useless unless
-fno-strict-aliasing is in effect.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26372
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* [Bug c/26372] opposite of may_alias attribute
2006-02-19 21:29 [Bug c/26372] New: opposite of may_alias attribute acahalan at gmail dot com
` (5 preceding siblings ...)
2006-02-22 3:28 ` acahalan at gmail dot com
@ 2006-07-19 3:48 ` pinskia at gcc dot gnu dot org
6 siblings, 0 replies; 8+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2006-07-19 3:48 UTC (permalink / raw)
To: gcc-bugs
------- Comment #7 from pinskia at gcc dot gnu dot org 2006-07-19 03:47 -------
(In reply to comment #6)
> Yes, char pointers are special. I'd like a non-special char pointer.
Actually it is not the char pointers which are special but access through a
character, there is a difference.
> I often know that a char pointer will never alias non-char data, but can not
> prove that it obeys all the complicated rules for __restrict.
restrict is actually less strict than what you want :). restrict attributed
pointers are can still alias other pointers, just not other restrict attributed
pointers.
> For non-char pointers the attribute would be useless unless
> -fno-strict-aliasing is in effect.
Even then it might be useless as -fno-strict-aliasing is huge hammer.
Also no feedback on an example in 3 months so closing.
--
pinskia at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|WAITING |RESOLVED
Resolution| |INVALID
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26372
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