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Re: An ImageMagick review (partial) [Was Re: [ITP - Ready for review]ImageMagick]


Sigh... the cat is already out of the bag. In the absence of a review I uploaded the package since it didn't seem that anyone was interested and this was the general pattern when I requested a review.

If Chris, Daniel, et al want to delete release/ImageMagick and clean it from setup.ini that is fine... otherwise we are going to have to provide compatibility packages if we change the layout significantly.

Thanks for the review anyway. I am going to bed though. It looks like anything other than the way I have done it now is going to take a lot of time to think through. Maybe it is best to just have a version that isn't perfect released so that people start using it and we have an incentive to actually get it right. :)


Charles Wilson wrote:

Harold L Hunt II wrote:

[The package now has plenty of votes and I have installed the package and tested the 'convert' command. I would like someone else to give the package at least a brief review before Daniel or I upload it.]

I would like to contribute and maintain ImageMagick:

ImageMagick 5.5.7 is a robust collection of tools and libraries offered under a usage license to read, write, and manipulate an image in many image formats (over 89 major formats) including popular formats like TIFF, JPEG, PNG, PDF, PhotoCD, and GIF.

Changes since initial ITP
1) Patched to actually stick LIBS onto the end of the libs passed to the linker, as the ImageMagick documentation says can be done.

2) Pass LIBS=-lcygipc to configure.

3) Pass --enable-shared to configure. Builds shared cygMagick-6.dll and cygMagick++-6.dll... drops each executable from 2+ MiB to roughly 10 KiB.

4) Create three packages instead of one: ImageMagick, libMagick6, and libMagick-devel.

5) Change my PATH before building so that 'convert' is not found in the Windows/System32/ directory.

I think that /usr/bin/Magick-config and /usr/bin/Magick++-config should be in the -devel package, instead of the main one. (ditto the man pages for them)

I think the entire /usr/lib/ImageMagick-5.5.7/ tree should be in its own versioned package: And the dll package and the main package should depend on it. But it definitely shouldn't be in the -devel package because the runtime queries it! Possible names:

  <or just stick 'em into the main ImageMagick-5.5.7-1 package>

The problem with 'ImageMagick6' is
(a) when 5.5.8 is released, IF the API hasn't changed and the DLLNUM stays '6', then no harm no foul. The new libMagick6 (from 5.5.8) will still require the matching ImageMagick6 (also from 5.5.8, using the /usr/lib/ImageMagick-5.5.8/ directory).

(b) Suppose for whatever reason, the API changes but the IM version does not -- perhaps due to a new choice of compilation options, or cygwin-specific patches that modify the API. Now you've got libMagick7 -- and ImageMagick7, presumably. But ImageMagick6 and ImageMagick7 can't coexist -- because they are both from the same 'upstream' version of ImageMagick and use the same dir in /usr/lib/.

(b1) "Don't do that". Fine -- but sometimes it has actually happened that I needed to bump the DLL version in the same upstream release. Say, for instance, when cygwin kernel 1.5 was released. So it DOES, in fact, occur.

(b2) "Don't version it at all" -- or keep it in the main package. Well, if you do that, then you can only have one "copy" at a time installed on your system. But if you have cygMagick-6.dll from 5.5.7 and, say, cygMagick-7.dll from 5.5.10 -- then cygMagick-6.dll is going to want /usr/lib/ImageMagick-5.5.7/* and cygMagick-7.dll is going to want /usr/lib/ImageMagick-5.5.10/*

Okay, I get that. So what about 'ImageMagick5_5_7'
(c) "What's the harm? Keep a separate sequence number for this set of files. Since it's the dirname "ImageMagick5.5.7" that causes the conflict, why don't we just use "5_5_7" for the vernum for this subpackage?" Well, that way all of these /usr/lib/ImageMagick-*/ directories can coexist. But

(d) Suppose you have to disable some codec in a build, where in 5.5.7-1 it was enabled, but in 5.5.7-2 is disabled. This does not actually change the API of the library itself (because codecs are on-demand loaded, via dlopen() if compiled externally, or via libtool's fake static dlopen() if compiled into the main dll). So there's no reason to bump the DLL version number. However, now the libMagick6 package depends on the ImageMagick5_5_7 package -- but the -1 version (ImageMagick5_5_7-5.5.7-1) advertises support for the newly disabled codec, while the -2 version (correctly) does not. So, you really need to ensure that the libMagick6 package and the ImageMagick5_5_7 package are upgraded together -- but there's no support, in setup.exe, for doing that -- unless you add ANOTHER level of versioning.

And in fact, that's often the way RPMs containing kernel modules are distributed:
with the version of the module AND the version of the kernel for which it is built.

But wait, there's more!

Now suppose that you succeed in building the codecs and filters as separate DLL's, instead of monolithically in the cygMagick-6.dll. NOW, the contents of /usr/lib/ImageMagick-5.5.7/modules-Q16/codecs/* really DO depend on cygMagick-6.dll -- not just vice versa. So, you really need BOTH the '6' AND the '5_5_7' as part of the package name for this group of files. Double double blech.

So, if you have to keep the stuff in /usr/lib/ImageMagick-*/ and the DLL tightly coupled as far as versioning goes, then it seems that what you really ought to do is just use 5_5_7 for the DLL version -- and issue a new DLL with each updated release. You can do this by using
"libXXXX_LDFLAGS = -release 5.5.7"
instead of
"libXXXX_LDFLAGS = -version-info 6:0:0

And then you'll get cygmagick-5-5-7.dll and stick it into libmagick5.5.7-5.5.7-1.tar.bz2; put the /usr/lib/ImageMagick-5.5.7/ stuff into ImageMagick5.5.7-5.5.7-1.tar.bz2, and all is well.

Except that now, if case (b) occurs, you're out of luck. Because you *can't* bump the DLL version number now that it is equivalent to the release number. (And another "problem" -- users will accumulate lots and lots of 'libmagickX.Y.Z' and 'ImageMagickX.Y.Z' packages, unless they manually remove them every now and then. All this is to support third party apps that may be compiled against cygMagick-5-5-7.dll etc.

And here's the final rub: back in the 20021102 timeframe, <src>/magick/ DID specify _LDFLAGS = -release $MAJ.$MIN.$MIC. Sometime between then and now, somebody deliberately decided to suddenly start following libtool guidelines, and use -version-info $LIBCUR:$LIBREV:$LIBAGE ! What a great time to start following the rules! (Unfortunately, I can't figure out when/who did this; when IM moved from to, they lost all CVS history older than about 5.5.5 it seems)

So, maybe you *shouldn't* revert back to -release versioning. I'd ask Bob F. what he was thinking...because 'strings cygMagick-6.dll' (or 'strings' on linux) shows that the /usr/lib/ImageMagick-X.Y.Z/modules-Q16/coders/ path is compiled into the DLL, which means that the interface really really DOES change with every release, so you might as well use -${MAJ}-${MIN}-${MIC} to name the shared library!


Now, I've taken a look at my original build of ImageMagick, and I've got a few questions based on that. Note that my build was from CVS ImageMagick between the 5.5.2 release and the 5.5.3 release, on 20021102 (slow release cycles, I guess: over one year to go from micro version .2 to .7) At that time, I was able to
1) build the codecs as separate DLLs
2) the 'main' DLL was named cygmagick-5-5-2.dll, as described above.
3) cygwin's libtool-1.5 is not actually stock libtool-1.5. There is a fix from Max Bowser for library search order (but that should have no effect here), plus a fix for the binary wrappers -- but that should only affect built-in testing and running the executables from the build dir[*]; it should have no effect on a fully installed ImageMagick.

[*] IIRC, this fix was actually occasioned by a failure to build PerlMagick -- because the PerlMagick configury needs to be able to run a proggie from the .build dir, but it invokes it via setting the $PATH and calling the proggie indirectly (which doesn't work on cygwin with stock libtool-1.5), instead of explicitly using /the/full/path/proggie (which DOES work on cygwin with stock libtool-1.5). So, it's just as well you're not building PerlMagick right now. :-)


I'm about to test the build procedure (but adding --with-modules) for your -src package, and install your binary for testing. Unfortunately, this involves some risk for me, as I can no longer find my binary tarball for IM-5.5.2...which is working fine. But I need to uninstall it before installing and testing yours. Perhaps I'll recreate my tarball using the /etc/setup/*.lst.gz file first. So patience, plz. :-)


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