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Re: make dist-lzma and make dist-xz


From: Peter Rosin
Subject: Re: make dist-lzma and make dist-xz
Date: Wed, 14 Dec 2011 14:29:06 +0100
User-agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:8.0) Gecko/20111105 Thunderbird/8.0

Stefano Lattarini skrev 2011-12-13 18:17:
> oOn Monday 12 December 2011, Peter Rosin wrote:
>> Hi!
>>
> Hi Peter.
> 
>> I noticed that the changes to "make dist-xz" to default to -e fixed
>> the xz.test on MinGW, but that lzma.test still fails (lzma: (stdin): Not
>> enough memory).
>>
> [BTW: thanks for your continuous testing with Cygwin and MinGW!]
> 
>> Hoping to fix the last fail in the testsuite, I looked
>> into adding something like LZMA_OPT or something to "make dist-lzma".
>> But in my cursory googling, I could not get my grips around what variable
>> to use. Does anyone know?
>>
> I don't, but I have another consideration: since lzma seems to be supersed
> by xz [1][2], couldn't we simply deprecate the `dist-lzma' option in this
> 11.1.2 version, and remove it altogether from the next major (or even minor)
> version?  WDYT?

That seems a bit drastic to me.

>> However, what I did find was that there is a variable named XZ_DEFAULT.
>> Shouldn't that be considered before "forcing" -e when XZ_OPT is missing?
>>
> From the xz manpage:
> 
>   XZ_DEFAULTS
>     User-specific  or  system-wide default options.  Typically this is
>     set in a shell initialization script to enable xz's memory usage
>     limiter by default.  Excluding shell initialization scripts and
>     similar special cases, scripts must never set or unset XZ_DEFAULTS.
> 
> So XZ_DEFAULTS is mostly meant to allow the user to set default memory
> usage limiters; since we don't touch such a setting in our use of
> XZ_OPT, I say we should be pretty safe.  Moreover:
> 
>   XZ_OPT
>     This is for passing options to xz when it is not possible to
>     set the options directly on the xz command line ...
>     Scripts may use XZ_OPT e.g. to set script-specific default
>     compression options.  It is still recommended to allow users
>     to override XZ_OPT if that is reasonable ...
> 
> and our use of XZ_OPT seems consistent with the advice given here.

Yes, I guess you are right.

I looked a bit further and it seems newer lzma compressors, probably those
implemented as symlinks to the xz binary, also respond to XZ_DEFAULTS and
XZ_OPT. So, I can make the lzma.test pass with XZ_DEFAULTS=--memlimit=250MiB
in the environment. I wonder how long that workaround will last...

However, older lzma binaries probably don't look at the XZ variables. So,
copying the XZ_OPT code from dist-xz to dist-lzma is probably a no-no.

Cheers,
Peter



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