[gentoo-java] Cross compiling for older platform versions

[gentoo-java] Cross compiling for older platform versions

[David Herron]

Hi, I talked with Petterati at FOSDEM last weekend and he explained to 
me (again) the issue y'all have.  I just noticed that Joe Darcy has 
posted a blog entry which seems to be really close to what you want.  
Namely that even if you specify "-source 1.4" the platform library is 
gonna change from release-release.  Please take a look.

http://blogs.sun.com/darcy/entry/how_to_cross_compile_for


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Re: [gentoo-java] Cross compiling for older platform versions

[David Herron]

David Herron wrote:
> Hi, I talked with Petterati at FOSDEM last weekend and he explained to 
> me (again) the issue y'all have.  I just noticed that Joe Darcy has 
> posted a blog entry which seems to be really close to what you want.  
> Namely that even if you specify "-source 1.4" the platform library is 
> gonna change from release-release.  Please take a look.
>
> http://blogs.sun.com/darcy/entry/how_to_cross_compile_for
>
>

Obviously I misremembered Petteri's name... sigh.
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Re: [gentoo-java] Cross compiling for older platform versions

[Petteri Räty]

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David Herron kirjoitti:
> Hi, I talked with Petterati at FOSDEM last weekend and he explained to 
> me (again) the issue y'all have.  I just noticed that Joe Darcy has 
> posted a blog entry which seems to be really close to what you want.  
> Namely that even if you specify "-source 1.4" the platform library is 
> gonna change from release-release.  Please take a look.
> 
> http://blogs.sun.com/darcy/entry/how_to_cross_compile_for
> 
> 

Yeah we talked a while ago on #gentoo-java or was it on this mailing 
list that our approach to backwards compatibility is not enough to be 
able to always run things with 1.4 but using -source is enough to get us 
through the following situation:

-appfoo depends on libfoo
-libb depends on liba but only compiles against 1.4 class library
-liba can be emerged with 1.6

So what I am trying to say here is that using -source 1.4 enables us to 
compile libb (if liba wasn't compiled to 1.4 bytecode, javac would fail 
with class version issues) but people should usually be running things 
with the latest stable JDK/JRE (this is what happens by default).

Regards,
Petteri




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Re: [gentoo-java] Cross compiling for older platform versions

[Petteri Räty]

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Marat Radchenko kirjoitti:
> Hi, Gentoo Java Team.
> 
> I'd like to share my thoughts on backwards-compatible compilation. As 
> you already said, specifying -source and -target is not enough because 
> different JDKs have different rt.jar. Solution is very simple - you just 
> need to specify -bootclasspath and point to rt.jar of target jre. The 
> only problem (he-he) is that you need to get it 
> somewhere. I see two options:
> 
> 1) Install target jre
> 2) Have separate package with rt.jar only.
> 
> Hope this info will be useful.
> 
> With best regards,
> Marat Radchenko
> 

Please don't top post. I already tried to explain that we don't 
necessarily need to make our jars work perfectly with older JDKs we only 
need the older bytecode so that we are able to compile things. If you 
really want backwards compatible jars just use *=sun-jdk-1.4 in 
jdk.conf. Should probably document this on the Java Guide.

Regards,
Petteri


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Re: [gentoo-java] Cross compiling for older platform versions

[Vlastimil Babka]

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Petteri Räty wrote:
> David Herron kirjoitti:
>> Hi, I talked with Petterati at FOSDEM last weekend and he explained to 
>> me (again) the issue y'all have.  I just noticed that Joe Darcy has 
>> posted a blog entry which seems to be really close to what you want.  
>> Namely that even if you specify "-source 1.4" the platform library is 
>> gonna change from release-release.  Please take a look.
>>
>> http://blogs.sun.com/darcy/entry/how_to_cross_compile_for
>>
>>
> 
> Yeah we talked a while ago on #gentoo-java or was it on this mailing 
> list that our approach to backwards compatibility is not enough to be 
> able to always run things with 1.4 but using -source is enough to get us 
> through the following situation:

Actually, this idea might be worth exploring when gen-1 is gone and some 
packages in gen-2 still need 1.4 to compile (but can run with 1.5+), 1.4 
EOL is near... Maybe taking rt.jar from blackdown-jdk would not break 
the license (didn't check), wouldn't need fetch restriction and because 
it would be just used as compilation target, the security 
vulnerabilities would be moot.

Or maybe there will be only few packages, with existing or easy patches 
to work with 1.5+ :)
-- 
Vlastimil Babka (Caster)
Gentoo/Java


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