Re: store reference detection

[Thomas Danckaert <post@thomasdanckaert.be>]

From: ludo@gnu.org (Ludovic Courtès)
Subject: Re: store reference detection (was Re: JARs and reference 
scanning)
Date: Thu, 27 Apr 2017 15:46:59 +0200

> Really? Qt/WxWidgets “hide” store references by default?

Not by default.  But there are cases were I've been bitten:

  - Qt has a “QStringLiteral”, which transforms your character literal
    to a UTF-16-encoded string at compile-time.  For example the
    kdbusaddons source used such a literal to encode the kdeinit5
    executable.  (In this case I patched the code, replacing it by a
    regular string.)

  - Similarly, when I packaged DVDStyler (a wxWidgets program), I
    noticed it also uses wchar_t strings to encode the name of
    executables.  (Here I used wrap-program to set the PATH, instead 
of
    embedding the full store location of the executables)

>> Does it make sense to expand the reference detecting code (perhaps
>> this would lead to too many different special cases?), or maybe
>> provide a mechanism to force references when the daemon cannot 
>> detect
>> them.  I suppose you can always add a text file with a list of 
>> store
>> items to the output, but maybe there's a more elegant way?
>
> ‘propagated-inputs’ is one way to manually specify run-time 
> references.
> It works at the package level and not at the store level—that is, 
> the
> store item’s references are unaffected by what ‘propagated-inputs’
> contains.  It’s usually enough for our purposes though.
>
> In that sense, I think jars are comparable to Python/Perl libraries,
> which do not carry reference information by themselves and thus 
> need a
> manually-provided ‘propagated-inputs’.

I think it's nice to avoid propagated inputs if possible, because 
they pollute the profile with things the user didn't strictly as for. 
 So Hartmuts proposed workaround (embed dependencies in the .jar's, 
if it's really possible, and use a .deps text file in the store to 
enable reference detection) sounds better.

Thomas