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digitalmars.D - GC-safe memory copying for D

reply Denis Shelomovskij <verylonglogin.reg gmail.com> writes:
Even `memcpy` is claimed dangerous at http://dlang.org/garbage.html
(because of possibility of moving GC, I suppose) but it just creates 
false positives for GC. `memmove` can even temporary destroy pointers in 
some overlapping cases like Google answer on "Lucky" `memmove source 
code` request does.

So I reinvented the wheel and created GC-safe `memmove` analog called 
`copyOverlapped` with comprehensive unittest coverage:
https://bitbucket.org/denis_sh/misc/src/tip/memutils.d

And I want this or such function to be included in druntime and be used 
in Phobos because using `memcpy`/`memmove` when even `memcpy` is called 
dangerous in docs looks incorrect and easily fixable.

P.S.
This post is inspired by bearophile's unanswered post titled  "Regarding 
a recent copy() fix" about really mysterious David Simcha's answer about 
`memmove`
http://d.puremagic.com/issues/show_bug.cgi?id=7484#c2
Mar 02 2012
parent reply "Robert Jacques" <sandford jhu.edu> writes:
On Fri, 02 Mar 2012 08:13:00 -0600, Denis Shelomovskij  
<verylonglogin.reg gmail.com> wrote:


 Even `memcpy` is claimed dangerous at http://dlang.org/garbage.html
 (because of possibility of moving GC, I suppose) but it just creates  
 false positives for GC. `memmove` can even temporary destroy pointers in  
 some overlapping cases like Google answer on "Lucky" `memmove source  
 code` request does.

 So I reinvented the wheel and created GC-safe `memmove` analog called  
 `copyOverlapped` with comprehensive unittest coverage:
 https://bitbucket.org/denis_sh/misc/src/tip/memutils.d

 And I want this or such function to be included in druntime and be used  
 in Phobos because using `memcpy`/`memmove` when even `memcpy` is called  
 dangerous in docs looks incorrect and easily fixable.

 P.S.
 This post is inspired by bearophile's unanswered post titled  "Regarding  
 a recent copy() fix" about really mysterious David Simcha's answer about  
 `memmove`
 http://d.puremagic.com/issues/show_bug.cgi?id=7484#c2


Is this CTFE compatible?
Mar 02 2012
parent reply =?ISO-8859-15?Q?Alex_R=F8nne_Petersen?= <xtzgzorex gmail.com> writes:
On 02-03-2012 16:25, Robert Jacques wrote:

 On Fri, 02 Mar 2012 08:13:00 -0600, Denis Shelomovskij
 <verylonglogin.reg gmail.com> wrote:


 Even `memcpy` is claimed dangerous at http://dlang.org/garbage.html
 (because of possibility of moving GC, I suppose) but it just creates
 false positives for GC. `memmove` can even temporary destroy pointers
 in some overlapping cases like Google answer on "Lucky" `memmove
 source code` request does.

 So I reinvented the wheel and created GC-safe `memmove` analog called
 `copyOverlapped` with comprehensive unittest coverage:
 https://bitbucket.org/denis_sh/misc/src/tip/memutils.d

 And I want this or such function to be included in druntime and be
 used in Phobos because using `memcpy`/`memmove` when even `memcpy` is
 called dangerous in docs looks incorrect and easily fixable.

 P.S.
 This post is inspired by bearophile's unanswered post titled
 "Regarding a recent copy() fix" about really mysterious David Simcha's
 answer about `memmove`
 http://d.puremagic.com/issues/show_bug.cgi?id=7484#c2


 Is this CTFE compatible?


Nope. It uses inline asm.

-- 
- Alex
Mar 02 2012
parent Denis Shelomovskij <verylonglogin.reg gmail.com> writes:
02.03.2012 19:29, Alex Rønne Petersen пишет:

 On 02-03-2012 16:25, Robert Jacques wrote:

 On Fri, 02 Mar 2012 08:13:00 -0600, Denis Shelomovskij
 <verylonglogin.reg gmail.com> wrote:


 Even `memcpy` is claimed dangerous at http://dlang.org/garbage.html
 (because of possibility of moving GC, I suppose) but it just creates
 false positives for GC. `memmove` can even temporary destroy pointers
 in some overlapping cases like Google answer on "Lucky" `memmove
 source code` request does.

 So I reinvented the wheel and created GC-safe `memmove` analog called
 `copyOverlapped` with comprehensive unittest coverage:
 https://bitbucket.org/denis_sh/misc/src/tip/memutils.d

 And I want this or such function to be included in druntime and be
 used in Phobos because using `memcpy`/`memmove` when even `memcpy` is
 called dangerous in docs looks incorrect and easily fixable.

 P.S.
 This post is inspired by bearophile's unanswered post titled
 "Regarding a recent copy() fix" about really mysterious David Simcha's
 answer about `memmove`
 http://d.puremagic.com/issues/show_bug.cgi?id=7484#c2


 Is this CTFE compatible?


 Nope. It uses inline asm.


But one can add if(!__ctfe) before inline assembler to make it CTFE-able 
(in theory, not tested).

And a better way is to add if(__ctfe) block at the beginning of a 
function with simple byte-by-byte copying (forward or backward) not to 
compile both asm and regular logic code.
Mar 02 2012