CVM (C++ Version Manager) is a tool designed to automate the management of C++ application dependencies, streamlining the installation process and reducing setup errors associated with various library and tool versions. It allows for user-level installation of components without requiring admin rights and can handle complex dependency graphs while ensuring compatible versions. CVM aims to provide an easy-to-use solution similar to Ruby's Bundler, simplifying the development and deployment of C++ applications.

1. Tribute to rvm
Introducing cvm
The best way to manage your C++ applications dependencies
Offirmo, 18/01/2013

2. cvm
C++ Version Manager
a tool
to automatically manage
your C++ application's dependencies

3. Once upon a time…
…there was a programmer…
…who was developping an honest C++
application…

4. 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)

5. 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...

6. ● Ubuntu 10.04 LTS (at that time, and make a better example ;)
● Clean, no packages installed
● Current situation :

7. ● 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 ../xyz
make
Fail !!!

8. ●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="…"
make Pain !!!
make install
● Default Wt is also too old : Pain!!!
git clone …
cmake ../… -PREFIX … -DCONFIGDIR …
make
Fail !!!
make install
--> but FAIL because Boost is too old !
● So for Boost :
...
Well, you get it…

9. Pain ! Fail ! %$# !
Completely value-less task !
Utter loss of time and energy !
Unworthy of us programmers !

10. proposed solution : the cvm tool
sudo apt-get install git
git clone git://github.com/Offirmo/cvm.git
cvm
(add cvm/bin to the path)
cvm
git clone git://github.com/abcd/myapp.git
myapp
cvm new myapp
cd myapp
cvm set_compfile Installation of
cvm update
cvm upgrade
dependencies
Done !
mkdir ../build
cd ../build
App build
cvm_exec cmake ../myapp
cvm_exec make

11. 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

12. The magic…
● Then cvm automatically setup the environment
so that all dependencies are met !
cvm set_compfile Set the « component file »
cvm update
compute dependencies
cvm upgrade (who needs what, which
version)
Install everything needed :
- use apt-get if possible
- download and build from
source else

13. 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

14. 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 ;)

15. 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

16. 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 !

17. 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)

18. 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)

19. Thank you !
https://github.com/Offirmo/cvm

20. Bonuses

21. Dependencies handling
Of 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

22. 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...

23. 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 required
require compiler.gcc
require lib.std
require lib.UnitTest++, version : 1.4+
# need a recent version
require lib.Boost, version : 1.51+
# sqlite is an optional dependency of Wt. We want a decent version
for some bugfixes
require lib.sqlite, version : 3.7+
# exact version of Wt + ensure that sqlite is built before
require lib.Wt, version : 3.2.3, require : lib.sqlite

24. 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)

25. 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