Once in a while I stumble over some cool cloud service like readthedocs.org (auto generating your documentation) or travis-ci.org (continuous integration build service), but I’ve always had the feeling that there were a ton of other cool services that I did not see.

Now I found a new service called leanstack.io that tries to solve exactly that problem. Leanstack keeps track of the new developer cloud services and keeps a nice categorized inventory for you to browse if you are looking for something concrete.

I recently had the need to install a newer version of the g++ compiler on Ubuntu 12.04 LTS. I documented the approach here.

Ubuntu does not typically release new toolchains for their stable versions, instead newer toolchains are made available in a PPA (Personal Package Archive) “https://launchpad.net/~ubuntu-toolchain-r/+archive/test“ to use the repository we can use the add-apt-repository command:

sudo add-apt-repository ppa:ubuntu-toolchain-r/test
sudo apt-get update
sudo apt-get install gcc-4.7 g++-4.7

Currently the PPA contains gcc/g++-4.7 and 4.8. After installing one or multiple of the newer versions we can use update-alternatives to switch between the different versions. The update-alternatives tool manages symlinks to the different installed versions and allow us to easily switch between them.

Before we add the new gcc/g++ lets check if we already have any alternatives setup by running:
$ update-alternatives --display gcc

If you don’t have any alternatives installed it will just print:
update-alternatives: error: no alternatives for gcc.

Lets see how to add an alternative:

$ sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-4.7 60 --slave /usr/bin/g++ g++ /usr/bin/g++-4.7
$ sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-4.6 40 --slave /usr/bin/g++ g++ /usr/bin/g++-4.6

As a default when we install new alternatives they are added to a group (in this case gcc) in automatic mode. This means that the link with the highest priority will become the default. In the case above we gave gcc-4.7 a priority of 60 and gcc-4.6 a priority of 40, so the default with be gcc-4.7
The –slave options tells update-alternative that when we change gcc it should also update the g++ links.

To check that everything is ok or to switch between the compilers we can use

$ sudo update-alternatives --config gcc
There are 2 choices for the alternative gcc (providing /usr/bin/gcc).

Press enter to keep the current choice[*], or type selection number: 0

That is more or less it. Running gcc --version shows that we are now using the newer version:

gcc (Ubuntu/Linaro 4.7.3-2ubuntu1~12.04) 4.7.3
Copyright (C) 2012 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

Recently I had the need to build a specific version (3.3) of the clang compiler from source. Following the instructions on the clang website this turned out to be quite easy. I recorded the steps here for future reference (steps adapted from http://clang.llvm.org/get_started.html):

1. Checkout llvm
svn co http://llvm.org/svn/llvm-project/llvm/tags/RELEASE_33/final llvm33_src

2. Checkout clang
cd llvm33_src/tools
svn co http://llvm.org/svn/llvm-project/cfe/tags/RELEASE_33/final clang
cd ../..

3. Checkout extra Clang Tools: (optional)
cd llvm33_src/tools/clang/tools/
svn co http://llvm.org/svn/llvm-project/clang-tools-extra/tags/RELEASE_33/final extra
cd ../../../../


4. Checkout Compiler-RT:
cd llvm33_src/projects/
svn co http://llvm.org/svn/llvm-project/compiler-rt/tags/RELEASE_33/final compiler-rt
cd ../..

5a. Building (Debug build)
mkdir llvm33_build
cd llvm33_build
CC=gcc CXX=g++ ../llvm33_src/configure
make -j8
cd ..

5b. Building (Optimized build)
mkdir llvm33_build
cd llvm33_build
CC=gcc CXX=g++ ../llvm33_src/configure --enable-optimized
make -j8
cd ..

Did you ever experience that a template error in C++ produced tons of terminal output, making the task of finding the actual offending error very tedious. Yesterday I stumbled upon a handy little tool called colout (http://nojhan.github.io/colout/).

You can install it using pip:
sudo pip install colout

No invoke the compiler (we redirect both stdout and stderr to the colout tool):
g++ main.cpp 2>&1 | colout error

Now you should see the word “error” nicely highlighted in red.