Re: Good but ... mk-origtargz Allow more files to be deleted than can fit inside argv (`getconf ARG_MAX`)

2018-01-24 Thread Ximin Luo 
Osamu Aoki:
> 
> Maybe before discussing technical solutions, we should know what issues
> we are addressing by this modification.  Is there a real cases which you
> need to have this patch?
> 

I need this for rustc. Try "apt-get source rustc" now and "uscan --verbose", it 
will fail. I had to locally patch mk-origtargz for it to work.

X

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Re: Good but ... mk-origtargz Allow more files to be deleted than can fit inside argv (`getconf ARG_MAX`)

2018-01-24 Thread Osamu Aoki 
Hi,

On Tue, Jan 23, 2018 at 03:58:11PM +0100, Mattia Rizzolo wrote:
> On Tue, Jan 23, 2018 at 10:58:53PM +0900, Osamu Aoki wrote:
> > This looks a reasonable patch.  But I don't know why you chose
> > 16384=0x400 as the max figure.
...  (It's ARG_MAX is in BYTEs but ...) 

> Jan 13 21:39:31    infinity0: why a magic number in the 
> mk-origtargz patch?
> Jan 13 21:43:10(instead of running a getconf and getting the 
> value and use it, I suppose)
> Jan 13 21:45:38(and then doing some computation to turn 
> number in something usable)
> Jan 13 21:50:07  jamessan[m]: it's `getconf ARG_MAX` / 128 
> which i felt was a reasonable path length for source filenames
> Jan 13 21:50:33  and worked in practise for me (larger values 
> like 3 broke)
> Jan 13 21:56:52infinity0: yes, but why not detecting it at 
> runtime (and a comment explaining why 128 is better than NAME_MAX=255)
> Jan 13 21:57:09  because it would involve more perl code
> 
> 
> So I agree.  Please don't merge that as it is until somebody does what's
> written here ↑.

Maybe before discussing technical solutions, we should know what issues
we are addressing by this modification.  Is there a real cases which you
need to have this patch?

I don't know perl at all but in rough idea in perl/python mix pseudo
code:

# suppose @args has all the filename paths

$max = `getconf ARG_MAX`;
$file = shift;
while #args > 0
$cmdline =  "command ";
while (total_length($cmdline) + len($file) -2 < $max) {
$cmdline = $cmdline . " " . $file;
$file = shift;
}
if ("command " != $cmdline ) {
shell_out_code($cmdline);
} else {
error_message;
}

Then it is guaranteed to be within ARG_MAX. But is these such case?

Osamu




> -- 
> regards,
> Mattia Rizzolo
> 
> GPG Key: 66AE 2B4A FCCF 3F52 DA18  4D18 4B04 3FCD B944 4540  .''`.
> more about me:  https://mapreri.org : :'  :
> Launchpad user: https://launchpad.net/~mapreri  `. `'`
> Debian QA page: https://qa.debian.org/developer.php?login=mattia  `-



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Re: Good but ... mk-origtargz Allow more files to be deleted than can fit inside argv (`getconf ARG_MAX`)

2018-01-23 Thread Ximin Luo 
Osamu Aoki:
> Hi,
> 
> [..]
> 
> This looks a reasonable patch.  But I don't know why you chose
> 16384=0x400 as the max figure.
> 
> Following your comment, I tried on my local machine
> $ getconf ARG_MAX
> 2097152
> 
> This is bigger than 16384.
> 
> If this is different on different system, why not dynamically check and
> set it with some safety margin like `getconf ARG_MAX` - 16 etc.?
> 

Hi Osamu, ARG_MAX is measured in bytes, not number of arguments.

I calculated 16384 as 2M / 128, 128 being a generously-high estimated value for 
"average path length" in debian packages.

I agree it would be clearer to replace 16384 with `getconf ARG_MAX / 
AV_PATH_LENGTH_EST` and define AV_PATH_LENGTH_EST = 128 near the top, but my 
perl knowledge is very basic and I wasn't sure of the best way to shell out to 
another program.

X

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Re: Good but ... mk-origtargz Allow more files to be deleted than can fit inside argv (`getconf ARG_MAX`)

2018-01-23 Thread Mattia Rizzolo 
On Tue, Jan 23, 2018 at 10:58:53PM +0900, Osamu Aoki wrote:
> This looks a reasonable patch.  But I don't know why you chose
> 16384=0x400 as the max figure.
> 
> Following your comment, I tried on my local machine
> $ getconf ARG_MAX
> 2097152
> 
> This is bigger than 16384.
> 
> If this is different on different system, why not dynamically check and
> set it with some safety margin like `getconf ARG_MAX` - 16 etc.?

Related lines from IRC:

Jan 13 21:39:31    infinity0: why a magic number in the 
mk-origtargz patch?
Jan 13 21:43:10(instead of running a getconf and getting the 
value and use it, I suppose)
Jan 13 21:45:38(and then doing some computation to turn number 
in something usable)
Jan 13 21:50:07  jamessan[m]: it's `getconf ARG_MAX` / 128 which 
i felt was a reasonable path length for source filenames
Jan 13 21:50:33  and worked in practise for me (larger values 
like 3 broke)
Jan 13 21:56:52infinity0: yes, but why not detecting it at 
runtime (and a comment explaining why 128 is better than NAME_MAX=255)
Jan 13 21:57:09  because it would involve more perl code


So I agree.  Please don't merge that as it is until somebody does what's
written here ↑.

-- 
regards,
Mattia Rizzolo

GPG Key: 66AE 2B4A FCCF 3F52 DA18  4D18 4B04 3FCD B944 4540  .''`.
more about me:  https://mapreri.org : :'  :
Launchpad user: https://launchpad.net/~mapreri  `. `'`
Debian QA page: https://qa.debian.org/developer.php?login=mattia  `-


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