Archive for July, 2011

DWARF-2 is a format to store debugging information. It is used on many ELF systems such as GNU/Linux. With the way things are compiled, there is a lot of redundant information in the DWARF-2 sections of an ELF binary.

Fortunately, there is an option to gcc that helps dealing with the redundant information and downsizes the DWARF-2 sections of ELF binaries. This option is -feliminate-dwarf2-dups.

Unfortunately, it doesn't work with C++.

With -g alone, libxul.so is 468 MB. With -g -feliminate-dwarf2-dups, it is... 1.5 GB. FAIL.

The good news is that as stated in the message linked above, -gdwarf-4 does indeed help reducing debugging information size. libxul.so, built with -gdwarf-4 is 339 MB. This however requires gcc 4.6 and a pretty recent gdb.

Lintian now has a warning for debian/rules missing build-arch and build-indep targets. As a dh user, I was surprised that some of my dh-using packages had this problem. And when looking at the source, I remembered how I came to this: GNU make is stupid.

Considering the following excerpt of the GNU make manual:

.PHONY

The prerequisites of the special target .PHONY are considered to be phony targets. When it is time to consider such a target, make will run its recipe unconditionally, regardless of whether a file with that name exists or what its last-modification time is.

And considering the following debian/rules:

.PHONY: build
%:
        dh $@

What do you think happens when you run debian/rules build in a directory containing a build file or directory?

make: Nothing to be done for `build'.

However, an explicit rule, like the following, works:

.PHONY: build
build:
        dh $@

It happens that many of the packages I maintain contain a build subdirectory in their source. As such, to work around the aforementioned issue, I just declared the dh rules explicitely, as in:

.PHONY: build binary binary-arch binary-indep (...)
build binary binary-arch binary-indep (...):
        dh $@

And this obviously doesn't scale for new rules such as build-arch and build-indep.

To be future-proof, I'll use the following instead:

.PHONY: build
build %:
        dh $@

I don't know why I didn't do that the first time...

With the upcoming changes in the beta and aurora channels (6.0 is going to reach beta, and 7.0 to reach aurora), the mozilla.debian.net repository is going to adapt, and drop versioned archives in favor of channel archives. The channel archives for beta and aurora already existed, however what is new is the "release" channel. Currently, that channel contains Iceweasel 5.0, but as soon as 6.0 is released, that's what the "release" channel will contain.

To summarize, if you added lines containing iceweasel-x.0 where x is 4, 5, or 6 in your /etc/apt/sources.list, you need to update it to the corresponding channel (don't forget 4.0 is dead, you should use "release" instead).

The iceweasel-5.0 and iceweasel-6.0 archives still exist at the moment but will be dropped as soon as the new aurora and beta releases are ready, which should be real soon now (only waiting for actual upstream releases).

As a somehow related note, it should be noted that Iceweasel 5.0 should (finally) enter Debian unstable on the 15th of July, at which point the latest 6.0 beta will also be uploaded to Debian experimental. It is still unclear how long it will take for Iceweasel 5.0 to reach Debian testing/wheezy, because of all the reverse dependencies, but when that happens, we'll also be able to push it to backports.debian.org.