Older blog entries for jamesh (starting at number 189)

Tracing Python Programs

I was asked recently whether there was an equivalent of sh -x for Python (ie. print out each statement before it is run), to help with debugging a script. It turns out that there is a module in the Python standard library to do so, but it isn't listed in the standard library reference for some reason.

To use it, simply run the program like this:

/usr/lib/python2.4/trace.py -t program.py

This'll print out the filename, line number and contents of that line before executing the code. If you want to skip the output for the standard library (ie. only show statements from your own code), simply pass --ignore-dir=/usr/lib/python2.4 (or similar) as an option.

BitKeeper

So the free (no-cost) version of BitKeeper has been discontinued, leaving just the commercial version and the limited open source version (which is essentially limited to checking out the head revision of a particular tree).

It seems a bit weird that one of the stated reasons for discontinuing the free version is a dispute with OSDL, where some employees were using BitKeeper (eg. Linus), while another unrelated employee was reverse engineering it as a personal project. This is a bit surprising, since it seems that a scenario almost the same as this was brought up last year and Larry said his concern was a licensed BitKeeper user helping someone else reverse engineer the code. Of course, there are probably other issues involved here.

This does bring up an interesting issue of what users of the free version are going to do with their repositories. While they can use the open source editing to easily check out the head revision and continue development, it isn't clear that it can be used to extract all the information stored in a repository. And since BitMover has refused to sell the commercial version to some people, it is conceivable that some projects could find themselves unable to access their revision history with BitKeeper.

I doubt this situation is acceptable to many users (they are using a version control system, so probably want to keep their revision history), so there will probably be some programs written to extract all the information from a BitKeeper repository. Ironically, this could add some value to BitKeeper for BitMover's commercial customers -- insurance for their data in case BitMover disappears or something else makes BitKeeper unusable to them.

Airports

If you are coming to Australia for first time, make sure you pack your camel suit and other valuable in your cabin luggage, rather than the checked luggage. It will save you trouble in the long run.

roozbeh: the Fedora EULA probably isn't a GPL violation (I'm sure Red Hat has legal advice that it is okay). Section 1 says "This agreement does not limit User's rights under, or grant User rights that supersede, the license terms of any particular component". So the EULA explicitly says that it doesn't limit any rights you received under the GPL. Section 2 goes on to say that your rights to copy or modify individual components of the distro are covered by the respective license.

What the EULA does cover is the particular compilation of the individual components making up the distribution. This is similar to the way a book publisher can claim copyright on a particular selection/ordering of poems that are in the public domain — while you can copy the individual poems, it would be a violation to copy the anthology as a whole.

The export controls section is just a restatement of the U.S. export regulations for cryptography, so wouldn't affect the non cryptographic portions. I'm not sure how this section would interact with the first section in the case of GPL'd/LGPL'd cryptography software though.

Eugenia's Article

I find it amusing how Eugenia selectively quotes mailing list posts to create an article about how Gnome doesn't care about what users want, and then in a follow-up asks that people don't take her article out of context.

New Gettext

While looking at the new version of gettext, I noticed the libgettextpo library. Starting with the new 0.14.2 release, this library now includes a .po file writer as well as a parser. I wonder if this could be useful for tools like intltool.

One of the other things I noticed in the new release was at the end of the NEWS file entry for the release:

* Security fixes.

It gives no indication of what those fixes are though, so I don't know how serious the problem is ...

Tim Tams

There are three new varieties of Tim Tams biscuits that came out recently. The weirdest of the three is chocolate and chilli. It tastes like a normal dark chocolate Tim Tam, but after you've finished it leaves a chilli aftertaste.

South Africa

I put up my photos from the trip to Cape Town online. Towards the end there are some photos I took while hiking up Table Mountain.

Building Gnome

It looks like with the Gnome 2.10 release, some packages fail to build from CVS if you are using a version of libtool older than 1.5.12. This is due to the way libtool verifies the version strings — in versions prior to 1.5.12, the check to make sure that the interface version numbers were non negative used a shell pattern that only matched numbers up to 3 digits long.

This might have seemd fine when it was coded, since how many libraries actually end up with more than 999 versions without breaking compatibility? However, many Gnome libraries are using noncontiguous interface version numbers so that releases on the stable branch can be assigned numbers guaranteed to be less than the versions released on HEAD.

So many 2.X libraries use X*100 as a base for the interface version number, which means with 2.10 we reach 1000 and things break. With libtool 1.5.12 and newer, the shell patterns have been modified to handle numbers up to 5 digits long, so it shouldn't cause a problem til we are ready to release Gnome 2.1000 (which will be due for release in about 250 years if the current schedule is maintained).

Mathematics Input

msevior: have you looked at the OpenOffice equation editor? It provides a fairly similar interface to what you've put together, with a few differences:

• In OpenOffice, the equation entry window is shown as a pane below the document in the main window.
• The OpenOffice equation entry syntax seems to be "TeX without the backslashes", which is a little less intimidating for new users (although if you already know TeX, it means that there is more to learn).
• Editing isn't completely one way. If you click on the parts of the equation in the top pane, it will move the cursor to the corresponding position in the bottom pane. I don't know how easy this would be with itex2mml, since I guess the transformation is one-way.

I agree with you that this style of input is a lot more usable than the Microsoft equation editor for people who understand Mathematics and need to enter a lot of it. The MS editor seems to be optimised for transcribing an equation from some other source, where you know exactly what it will look like from the start. In contrast, the text interface makes it as easy to rearrange an equation as it is to rearrange the rest of the text in the document.

South Africa

From the conditions of residence at the place I'm staying:

5. Where appropriate the masculine gender shall include the feminine gender and vice versa and the singular shall include the plural.

Bush fire

When I woke up this morning, there was a lot of smoke in the air from the bush fire up in the hills east of Perth. The smoke is so thick that some buildings less than a kilometer away are only just visible. Also, sunlight filtering through the smoke gives everything a yellow tinge.

It hasn't burnt down any houses yet, and hopefully the fire services will get it under control before it does.

GraphViz

On the gtk-doc-list mailing list, Matthias mentioned that the GraphViz license has been changed to the CPL (the same license as used for Eclipse), which is considered Free by both the FSF and OSI (although still GPL incompatible). This should remove the barriers that prevented it getting packaged by Linux distributions.

Due to the previous licensing, RMS urged developers of GNU software to not even produce output in the form that the GraphViz tools use as input. Maybe that can change now. While the license is GPL incompatible, the GraphViz tools can easily be invoked from the command line, passing a .dot file in, and getting output in PNG, PS, SVG, etc format (or even another .dot file with the layout information added), which is enough for pretty much all uses of the tools.

One of the features I added to JHBuild fairly early on was the ability to dump the dependency tree for a set of modules in the .dot format. So to visualise the dependencies for Gnome, you could run a command like this:

jhbuild dot meta-gnome-desktop | dot -Tps > gnome-2.10.eps

(of course, given the number of modules that are needed to build the entire Gnome desktop, you might get a better picture by picking a smaller number of modules).

Travels

I've put some of the photos from my trip to Mataró, and the short stop over in Japan on the way back. The Mataró set includes a fair number taken around La Sagrida Familia, and the Japan set is mostly of things around the Naritasan temple (I didn't have enough time to get into Tokyo).

Multi-head

A few months back, I got a second monitor for my computer and configured it in a Xinerama-style setup (I'm actually using the MergedFB feature of the radeon driver, but it looks like Xinerama to X clients). Overall it has been pretty nice, but there are a few things that Gnome could do a bit nicer in the setup:

• Backgrounds get stretched over both screens. The Ubuntu backgrounds already looked a bit weird at a 5:4 aspect ratio. They look even worse at a 5:2 ratio :-). Ideally the background image would be repeated on each monitor of the virtual screen. Some details are available as bug 147808, but it looks like the fix would be in EelBackground code.
• Most parts of the desktop treat the monitors as independent (which is good, since most people pick Xinerama over classic X multi-screen so that dragging windows between monitors works, rather than to build video walls), but there is a few bits that don't. One of the more obvious ones is in Metacity: the alt+tab dialog pops up centred on the monitor where mouse currently resides, but it cycles through all the windows visible on the virtual screen. This is a bit confusing, since it looks like it will be a monitor-local operation based on the position of the dialog (however, if it was monitor-local I'm not sure how you'd switch focus to a window on the other monitor with only the keyboard ...).

Bazaar

The new merge command in baz is quite nice. This provides support for merging in ways that tla can't. One of the limitations of star-merge is that it can get confused if you don't strictly follow the star topology when merging. That is, you should only merge to/from the person you branched from, and people who branched from you. If siblings merge for instance, it can cause problems with subsequent merges.

The new merge command doesn't suffer from that problem, and allows you to merge from anyone. Of course, if you break the star topology, people wanting to merge from you will either need to be using Bazaar, or ask for you to merge from them first (so that the star-merge algorithm merges the right changes).

Mataró

The conference has been great so far. The PyGTK BoF on the weekend was very productive, and I got to meet Anthony Baxter (who as well as being the Python release manager, wrote a cool VoiP application called Shtoom). There was an announcement of some of the other things Canonical have been working on, which has been reported on in LWN (currently subscriber only) among other places.

Over the weekend, I had a little time to do some tourist-type things in Barcelona. I went to La Sagrada Família. It was a great place to visit, and there was an amazing level of detail in the architecture. You can walk almost to the very top of the cathedral, and see out over the Barcelona skyline (and see various bits of the cathedral not visible from the ground). I'll have to put my photos up online.

Bazaar

I've been using using Bazaar a bit more at work, and it is becoming quite usable, compared to tla. It is a little interesting using daily builds of baz from the 1.1 development branch, where some features appear, get renamed or removed as they get developped, but it has a few more useful features not found in the 1.0 release. From a user point of view, it feels like the command line interface for baz is being designed to be easy to use, while tla's feels like they made choices based on what was easy to implement.

I built some Fedora Core 2 i386 builds of the 1.0.1 release, and some 1.1 snapshots that are now up on the Bazaar website in case anyone wants to try them. When I get back home and install FC3 onto my AMD64 box (it only has Ubuntu on at the moment), I'll do some FC3 x86-64 and i386 builds too.