icu 50 and how to identify dependents

[Jeremy Huddleston Sequoia]

On Feb 10, 2013, at 1:27 AM, Ryan Schmidt <ryandesign at macports.org> wrote:

>> You should check 'nm -m <binary>' to determine what it actually uses.  glibtool is just overzealous and assumes that it's safer to have the final executable link against *everything*.    We'd be doing ourselves a favor if we forced a global post-destroot that just deleted ${prefix}/lib/*.la and added a verification step that ensured every link was actually relevant.
> 
> I haven't used the nm tool before and am not familiar with its output.

nm shows you what symbols are provided by the binary and which symbols it needs.  With 'nm -m' you will see more verbose output including where the library resolves undefined symbols to.  As a quick example of how much crud is being linked which isn't needed, this first line shows what libpangocairo actually needs:

~ $ nm -m /opt/local/lib/libpangocairo-1.0.dylib | grep 'undefined' | sed 's:^.*(from \(.*\)).*$:\1:' | sort -u
libSystem
libcairo
libfontconfig
libfreetype
libglib-2
libgobject-2
libpango-1
libpangoft2-1

And this is what it's linking against:

~ $ otool -L /opt/local/lib/libpangocairo-1.0.dylib
/opt/local/lib/libpangocairo-1.0.dylib:
	/opt/local/lib/libpangocairo-1.0.0.dylib (compatibility version 3201.0.0, current version 3201.5.0)
	/opt/local/lib/libpango-1.0.0.dylib (compatibility version 3201.0.0, current version 3201.5.0)
	/opt/local/lib/libcairo.2.dylib (compatibility version 11203.0.0, current version 11203.12.0)
	/opt/local/lib/libpixman-1.0.dylib (compatibility version 29.0.0, current version 29.2.0)
	/opt/local/lib/libpng15.15.dylib (compatibility version 30.0.0, current version 30.0.0)
	/opt/local/lib/libxcb-shm.0.dylib (compatibility version 1.0.0, current version 1.0.0)
	/opt/local/lib/libX11-xcb.1.dylib (compatibility version 2.0.0, current version 2.0.0)
	/opt/local/lib/libxcb-render.0.dylib (compatibility version 1.0.0, current version 1.0.0)
	/opt/local/lib/libXrender.1.dylib (compatibility version 5.0.0, current version 5.0.0)
	/opt/local/lib/libXext.6.dylib (compatibility version 11.0.0, current version 11.0.0)
	/opt/local/lib/libX11.6.dylib (compatibility version 10.0.0, current version 10.0.0)
	/opt/local/lib/libxcb.1.dylib (compatibility version 3.0.0, current version 3.0.0)
	/opt/local/lib/libXau.6.dylib (compatibility version 7.0.0, current version 7.0.0)
	/opt/local/lib/libXdmcp.6.dylib (compatibility version 7.0.0, current version 7.0.0)
	/opt/local/lib/libpangoft2-1.0.0.dylib (compatibility version 3201.0.0, current version 3201.5.0)
	/opt/local/lib/libgmodule-2.0.0.dylib (compatibility version 3401.0.0, current version 3401.3.0)
	/opt/local/lib/libharfbuzz.0.dylib (compatibility version 913.0.0, current version 913.0.0)
	/opt/local/lib/libgobject-2.0.0.dylib (compatibility version 3401.0.0, current version 3401.3.0)
	/opt/local/lib/libgthread-2.0.0.dylib (compatibility version 3401.0.0, current version 3401.3.0)
	/opt/local/lib/libffi.6.dylib (compatibility version 7.0.0, current version 7.0.0)
	/opt/local/lib/libglib-2.0.0.dylib (compatibility version 3401.0.0, current version 3401.3.0)
	/usr/lib/libresolv.9.dylib (compatibility version 1.0.0, current version 41.1.0)
	/opt/local/lib/libintl.8.dylib (compatibility version 10.0.0, current version 10.2.0)
	/opt/local/lib/libiconv.2.dylib (compatibility version 8.0.0, current version 8.1.0)
	/usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 125.2.11)
	/opt/local/lib/libgraphite2.3.dylib (compatibility version 3.0.0, current version 3.0.1)
	/opt/local/lib/libicule.49.dylib (compatibility version 49.0.0, current version 49.1.2)
	/opt/local/lib/libicuuc.49.dylib (compatibility version 49.0.0, current version 49.1.2)
	/opt/local/lib/libicudata.49.dylib (compatibility version 49.0.0, current version 49.1.2)
	/opt/local/lib/libfontconfig.1.dylib (compatibility version 8.0.0, current version 8.2.0)
	/opt/local/lib/libfreetype.6.dylib (compatibility version 16.0.0, current version 16.0.0)
	/opt/local/lib/libz.1.dylib (compatibility version 1.0.0, current version 1.2.7)
	/opt/local/lib/libbz2.1.0.dylib (compatibility version 1.0.0, current version 1.0.6)
	/opt/local/lib/libexpat.1.dylib (compatibility version 8.0.0, current version 8.0.0)
	/System/Library/Frameworks/ApplicationServices.framework/Versions/A/ApplicationServices (compatibility version 1.0.0, current version 38.0.0)

> We just had a release of MacPorts so it might be awhile before we have another one, and any such global post-destroot to remove .la files would have to be coded first, and its consequences understood.

Well, it's consequences are that glibtool will no longer propagate dependencies like a virus.

> Meanwhile, what do we do today? Not update icu?

No, icu is actually kind of important … and unfortunately, it's kind of a root project.  I'm not sure the best answer here.

> And what will we do once the .la removal code you talk about is added? Won't we have to revbump almost every port?


At minimum, we should poke the buildbots to do a rebuild.  I don't think a revbump would be warranted for every port.  The situation would clear itself up as ports bumped themselves.  The risk in not bumping is that someone might still have a viral link which we didn't account for when we update something again in the future, but rev-upgrade should catch those cases.

--Jeremy