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Introducing cvm
Offirmo, 18/01/2013
The best way to manage your C++ applications dependencies
Tribute to rvm
cvm
C++ Version Manager
a tool
to automatically manage
your C++ application's dependencies
Once upon a time…
…there was a programmer…
…who was developping an honest C++ application…
His C++ app was not standalone…
His app was based on a C++ lib called :
He was using of course.
He was also unit-testing using : UnitTest++
…and using cmake to build. (and gcc of course)
One day, the app got (somewhat) ready to go in production.
The programmer set up a clean linux box and began installing his app… (Note : it's a server app)
Then the troubles arrived...
● Ubuntu 10.04 LTS (at that time, and make a better example ;)
● Clean, no packages installed● Current situation :
● My app : git clone https://github.com/abcd/xyz● So I need git : sudo apt-get install git
● Need gcc & co. : sudo apt-get install build-essentials● Need wt : sudo apt-get install witty witty-dbg witty-dev
● Need Boost : sudo apt-get install libboost-dev● Nedd UnitTest++, which has no packet :
wget …
make (yes, it's a very simple lib)
● Need cmake : sudo apt-get install cmake● Let's compile :
cmake ../xyzmake
Fail !!!
● First cmake can't find UnitTest++ that I installed manually in a custom dir, so :
export … (have fun with pathes)
● Then cmake of Ubuntu 10.04 is too old for my app, I need to install latest from source :
wget …./bootstrap --prefix="…"makemake install
● Default Wt is also too old :git clone …cmake ../… -PREFIX … -DCONFIGDIR …makemake install--> but FAIL because Boost is too old !
● So for Boost :...
Well, you get it…
Pain !!!Pain!!!
Fail !!!
Pain ! Fail ! %$# !Completely value-less task !
Utter loss of time and energy !Unworthy of us programmers !
proposed solution : the cvmcvm tool
sudo apt-get install gitgit clone git://github.com/Offirmo/cvmcvm.git(add cvmcvm/bin to the path)git clone git://github.com/abcd/myappmyapp.git
cvmcvm new myapp
cd myappcvmcvm set_compfilecvmcvm updatecvmcvm upgrade
mkdir ../buildcd ../buildcvm_execcvm_exec cmake ../myappcvm_execcvm_exec make
Done !Installation of dependencies
App build
The magic…
● The app provides a «component file» listing its dependencies :
(simplified)
# As far as I know, no particular gcc version is required require compiler.gcc require lib.std
# need a recent version require lib.UnitTest++, version : 1.4+
# need a recent version require lib.Boost, version : 1.51+
# need a recent version require lib.Wt, version : 3.2.3
The magic…
● Then cvm automatically setup the environment so that all dependencies are met !
cvmcvm set_compfile
cvmcvm update
cvmcvm upgrade
Set the « component file »
compute dependencies (who needs what, which version)
Install everything needed : - use apt-get if possible - download and build from source else
The magic…
● Of course, cvm must know about the components :● corresponding apt packets● download url● how to build them● ...
● So cvm has a database of components
Does it ring a bell ?
● Other languages have such a tool for a while● ex. ruby "bundler" http://gembundler.com/
● It's a shame that C++ still didn't have it !● Fixed ;)
More awesomness...
● cvm installs everything in user-land● No need to be admin (except for apt-get install)
● cvm doesn't mess with the env vars● set them on demand, hence the cvm_exec wrapper
● cvm can ensure exact components versions● Perfect for production environment
● cvm can maintain separate sets of components● So you can have different versions of the
components for different apps/versions
More awesomness...
● cvm has more nice features● Not listed here for brievity, see «bonuses»
● cvm is easy to install● Just bash scripts !
● cvm is totally free● Copyfree license, do whatever you want with it !
Current status
● cvm works (at last for me on my machine ;)● It is still rough :
● compfile syntax still in progress● multi-users usage needs to be enhanced● only 16 components at this time (jan-2013)
● But easy to add some !● Code and architecture would benefit from a little cleanup to ease contributions
● Comments and suggestions are welcomed !● Fork me on github ! (doc on internals coming soon)
One more thing...
● Why c.v.m. ?● Because of rvm (ruby version manager) https://rvm.io/
● Like rvm, cvm is meant to play with multiple compilers : gcc 4.7 (for C++11), clang...● This feature is not available yet (jan-2013)
Bonuses
Dependencies handlingOf course, cvm computes dependencies recursively and resolves them.
Example 1 : My app --> Boost 1.49+ My app --> Wt 3.2.3 --> Boost 1.41+ --> Latest known Boost newer or equal to 1.49 will be installed
Example 2 : My app --> Boost 1.40 (exact version) My app --> Wt 3.2.3 --> Boost 1.41+ --> Error ! cvm can't resolve those conflicting requests
The real dependency graph of my app is :
The orange parts are non-trivial to install on my target OS (no correct packet)
While developping, I installed everything by hand when needed. Then I forgot about it...
The corresponding compfile is…## C++ VM component set definition## see https://github.com/Offirmo/cvm#### Thanks to this file and the C++VM tool,## all exact dependencies are installed.
cvm_minimum_required_version 1.0
# As far as I know, no particular gcc version is requiredrequire compiler.gccrequire lib.std
require lib.UnitTest++, version : 1.4+
# need a recent versionrequire lib.Boost, version : 1.51+
# sqlite is an optional dependency of Wt. We want a decent version for some bugfixesrequire lib.sqlite, version : 3.7+# exact version of Wt + ensure that sqlite is built beforerequire lib.Wt, version : 3.2.3, require : lib.sqlite
Additional features● cvm automatically set env vars needed by autotools and cmake, so they correctly find the manually installed libs (over the system one)● cvm can automatically detect headers for libs that don't provide a «make install»● cvm automatically creates a folder with all headers so you can provide it to your IDE code indexer (ex. Eclipse)● cvm try to save resources by caching common resources : downloaded archives and source code (src not duplicated if out-of-src build is available)
Links :● https://rvm.io/● http://gembundler.com/
S/O● http://stackoverflow.com/q/14263324/587407● http://stackoverflow.com/q/1827705/587407
Image credits :● http://tecfa.unige.ch/tecfa/teaching/UVLibre/0001/bin17/troubles.html● wikipedia
