Examining multiple cores with gdb and grep

So you've got a bunch of core files from a failing application. You look in one of them and find what's causing that particular error. However you're not sure whether all the cores are caused by the one same issue.

The application I was having trouble with was a multithreaded app, so I couldn't rely on the stacs being identical every time... so this is what I did.

stackdumper.gdb Then in bash:

In my case I found that string in all 80 cores, so I know that was the only issue.

Javascript databindings with observers

This is not quite as clear as the previous post, but heres a version of my javascrip prototyping with observers on the data. Again you can play with it using jsfiddle .. or heres the code.

Creating data bindings using javascript closures

I've been working on javascript codebase that stores all its data in forms, hiding and showing all the form elements as the view changes. This has worked well while the structure of the data was relatively rigid. But now we've got dynamically structured (tree-like) data we need to be able to grow and shrink the views in more flexible ways.

While I'm not a gung-ho MVC advocate, it certainly looked like the app could do with a bit of an MVC style cleanup (the data was in the view rather than being accessed by the view).

The problem was it wasn't clear how to get the data out of the view... here's a simplified version of the method I'm planning to use.


You can also play with this using jsfiddle

I'm thinking about implementing broadcasting of changes and more model based approach later... but maybe that'll have to be another post.

Gits prepare-commit-message hook

So I often write bad commit messages. At best they're inconsistent - sometimes with ticket ids at the start sometimes with ticket ids at the end. Sometimes only a short message, sometimes a nicely formatted bullet point list.

Thankfully git has a tool to help you get these things consistent. Its called the "prepare-commit-msg hook"

I wrote a little python script to make a default commit message. Its not perfect but it should help... It takes the branch name, searches for a version tag and removes it, then searches for anything that might be a ticket id and adds it to the message. Finally it adds some boilerplate.

Command line git trees

Often I'm stuck in a terminal and want to see the commit history in a nice tree format. There's a nice solution ... git log recently learnt the "--graph" feature.

You can get pretty nice results from "--graph --oneline"

But using the tricks from http://www.jukie.net/bart/blog/pimping-out-git-log we can get a much nicer result - including author and branches and time all coloured nicely

Rendering maths from a web page

Occasionally I do pretty math intensive coding.
And one of the best pieces of software for writing about maths is TeX.
It was written by one of the gurus/fathers of modern computer science in 1978, and is still in use all over the world. So when it comes to putting math on the web, it used to be a workflow like this

• render math using tex
• copy and paste somewhere
• add an image link to your docs.

However some clever people have made that process so much easier: Two efforts in particular look very nice

• TeX Formulas - from the Google Chart API
• MathJax

Heres some mathjax : $ \nabla \times \vec{\rho} = 0 $
Heres the same thing using the google api:

I think the mathjax is nicer, but the google charts version is easier to integrate.

Using saru with googlemock and googletest

Saru (earlier blog post) is my little testing framework. It does everything we need. It's been used in several serious software development situations. But sometimes things are a little painful.

For example, saru doesn't come with any nice mocking helpers for C++. There is a basic C++ testing library that comes with it, but writing your own mocks by hand is one of those painful things I mentioned.

Thankfully there's a nice mocking library for C++ from the folks at google, called oddly enough, googlemock. However googlemock is designed to work with googletest - the google testing framework.

Googletest is also great. But its orthogonal to saru, rather than competitive. Saru is cross-language and designed to be more of a test-running wrapper, while googletest is a c++ unit testing library.

So I had three options if I wanted to use google-mock with my code and saru.

1. Make the google-mocks work with the saru-cxx library.
2. Make google-test output in a format that saru could digest.
3. Make saru able to parse google-test output.

IMO the third is the wisest and most extensible option. Luckily the changes were pretty easy.

So now getting a google-test file working in saru is as trivial as adding a

\\SARU : Format gtest

to the top of the test file.. and everything just works :)
(Well you'll need to make sure the compiler can find the right includes and the gtest library.. but thats all)

For example I get this kind of output when running a test suite.

99-misc-00-periodic-processor.cpp::TestFixture::test_process_many : OK
gmock_test.cpp::PartyTest.CallsDance : OK
gmock_test.cpp::PartyTest.CallsDanceFails : FAILED
==MESSAGE==

==STDERR==
gmock_test.cpp:69: Failure
Value of: p.party()
  Actual: false
Expected: true