[Nice] Compilation of libnice code

[Youness Alaoui]

Hi Daniel,

On 02/15/2013 11:27 AM, Daniel Lobo wrote:
> This is not a question, but some kind of help for people with problems compiling
> libnice examples. I was very surprised to find that no one ever asked how to
> compile code using libnice, seeing as instructions were impossible for me to
> find. Am I missing something really obvious?
> 
Thanks for writing this, I'm sure others will find some of its content useful.
As for instructions. Maybe I should write build instructions in the README file.
> 
> Anyway, I have, for the past 4 days, been trying to compile and use a C/C++
> library that allows P2P communication for my project. After giving up for now on
> the massively hard libjingle (hard to compile, hard to understand, examples with
> thousands of lines...), I tried libnice.

haha, yes, libjingle is a huge huge mess. libnice itself was written so we could
get rid of libjingle! You'll find libnice to be much easier to work with :)

> 
> 
> Compiling the library (Windows and Linux):
> 
> I successfully compiled libnice under Windows, using VS (just follow the readme
> given in the libnice package), and under Linux. If you are compiling libnice in
> Linux, and are unexperienced like I am (the readme instructions are
> nonexistent), know that you have to run (inside the libnice folder) ./autogen.sh
> (run "chmod +x autogen.sh" if it gives errors about permissions), ./configure,
> make, sudo make install, in this order.
Great! The README.win32 and VS support was added by "Filippo Della Betta" who
sent his patches to this mailing list. I'm glad they were helpful to you! If you
find anything was missing, let me know and we could enhance/modify the readme
file to help others.
As for linux, there were no build instructions because the "./configure && make
&& sudo make install" is the 'standard' way of compiling anything on Linux. If
you need to compile stuff on linux, then you should know that magic sequence of
commands! To me at least, explicitely saying it is kind of like saying in the
windows instructions "in Visual Studio, go to menu build, and click the Build
button" :)
As you are new to linux, it's perfectly understandable that you didn't know
this, but at least now, you do. I will add build instructions in the README file
so other unexperienced liux users will not go through the same trouble as you did.
As for the ./autogen.sh, that's also the standard way of generating the
configure file. That's only necessary if you download the source from git, but
you don't need to do it if you download a release version since the configure
file is always pre-generated in those tarballs.

> 
> You *might* need to do some apt-gets before (glib-2.0?), but I can't remember if
> that was true for me (I tried loooots of things when attempting to build). If
> this is the case, I'm sorry that I can't help enough, but I can't remember all
> that I did (besides, I believe you can find most errors on the web, and they
> should direct you to some missing library that can be acquired with apt-get).
As far as I remember, libnice has no dependencies other than glib. So you
probably had to do apt-get install libglib-2.0-dev. There are also dependencies
on gstreamer and on gupnp, but if those are not found during the ./configure
stage, then their respective features will simply be disabled and libnice will
compile without them.



> 
> 
> Compiling examples:
> 
> After compiling, the thing was: I couldn't (and still can't) find instructions
> on how to compile libnice examples, or what libraries and paths to include. I
> tried to compile the example at
> http://nice.freedesktop.org/libnice/NiceAgent.html (inside a main method and
> using #include "agent.h") but I had to do a lot of trial and error on code
> callbacks, linkage libraries, include paths, etc. Besides, there was an
> undeclared variable "rcands" and, as of this writing, I still haven't understood
> the theory about candidates.
The example there is more of a pseudo-code than an actual compilable example. It
is only meant to be read and to allow you to understand which API functions to
call and when. That's also why it couldn't compile and had missing variables, etc...
Until very recently (thanks Bryce Allen who contributed it), we never had real
examples with libnice. Most people would just read the documentation and the
unit tests to see how to use the library.
You can now find these examples here :
http://cgit.collabora.com/git/user/kakaroto/libnice.git/tree/examples
They will be included in the next release of libnice (to be released very soon).
As you can see from the comment in the header of those files, they can be built
with :
 * Build:
 *   gcc -o simple-example simple-example.c `pkg-config --cflags --libs nice`

pkg-config is the standard tool on linux for defining which compiler flags and
options and libraries are needed when you compile a program that depends on the
library.
However, in the case of those examples, simply typing "make" will get them to
compile now that they are part of libnice's build system.

> 
> I finally gave up after many many many undefined references of various kinds.
> 
> The ONLY thing that did save me was something called pkg-config.
> 
> Apparently, pkg-config is a tool that knows what flags you have to use when
> compiling and linking your code with some libraries. One of the libraries which
> it can help is "nice" (libnice).
> 
Yep, libnice installs the file 'nice.pc' to /usr/lib/pkgconfig which allows
pkg-config to find which version of libnice is installed, what C flags to pass
to the compiler and what LD flags and dependent libraries to pass to the linker.
As I said above, it's the standard way on linux of checking for dependencies and
compiling programs with their dependent libraries. For example, libnice (and
pretty much every other software out there) uses pkg-config to check for the
existence and versions of their dependencies and to link with them. In the
configure.ac file, you will see this line :
PKG_CHECK_MODULES(GLIB, [dnl
        glib-2.0 >= 2.13 dnl
        gobject-2.0 >= 2.13 dnl
        gthread-2.0 >= 2.13 dnl
        gio-2.0 >= 2.13 dnl
        ])
This will check for all these modules (glib-2.0, gobject-2.0, gthread-2.0 and
gio-2.0) and will store the appropriate C flags and LD flags and dependencies in
GLIB_CFLAGS and GLIB_LIBS variables to be used in the makefile.



> 
> Eclipse:
> 
> If you are using Eclipse, like me, go to "Help -> Install New Software...", use
> http://petrituononen.com/pkg-config-support-for-eclipse-cdt/update as the "Work
> with" site and select and install the plugin.
> 
> Then, on your project with the examples you want to run, go to Properties ->
> C/C++ Build -> Pkg-config tab and select "nice". That should set the correct
> includes, flags and libraries in the "Tool Settings" tab. Now it's hopefully
> just a matter of using the right #includes in your code.
> 
> For those without Eclipse and wanting to know the paths and libraries, this is
> what pkg-config gave me in Linux:
> 
> GCC C/C++ Compiler -> Includes -> Include paths (-I):
> /usr/include/glib-2.0
> /usr/lib/x86_64-linux-gnu/glib-2.0/include
> /usr/local/include/nice
> 
> Compiler (C or C++) -> Miscellaneous -> other flags:
> -pthread
> (in addition to -c -fmessage-length=0)
> 
> GCC C++ Linker -> Libraries -> Libraries (-l):
> nice
> gthread-2.0
> rt
> gio-2.0
> gobject-2.0
> glib-2.0
> nice
> gthread-2.0
> rt
> gio-2.0
> gobject-2.0
> glib-2.0
> 
> GCC C++ Linker -> Libraries -> Library search path:
> /usr/local/lib
> 
> If it helps, Eclipse ended up doing something like:
> 
> Compiler:
> g++ -I/usr/include/glib-2.0 -I/usr/lib/x86_64-linux-gnu/glib-2.0/include
> -I/usr/local/include/nice -O0 -g3 -Wall -c -fmessage-length=0 -pthread -MMD -MP
> -MF"test.d" -MT"test.d" -o "test.o" "../test.cpp"
> 
> Linker:
> g++ -L/usr/local/lib -o "libnice_tests"  ./test.o   -lnice -lgthread-2.0 -lrt
> -lgio-2.0 -lgobject-2.0 -lglib-2.0 -lnice -lgthread-2.0 -lrt -lgio-2.0
> -lgobject-2.0 -lglib-2.0
> 

Thanks for that, this looks useful, would you mind if I included parts of it in
the build instructions of the README ?

> 
> pkg-config in Linux:
> 
> You can naturally also download and run pkg-config by itself (without Eclipse)
> to get all of this, but I didn't do this so please bear with me and search the
> web for a bit on the generic way to use pkg-config :) It should be something
> like: gcc -o test test.c `pkg-config --libs --cflags glib-2.0`
> 
Yep, that would do the trick, it should be installed on your system though since
I think pretty much everything would depend on it! If you want to compile
something, you would usually install gcc, autotools and some -dev packages and I
think pkg-config comes with them automatically as a dependency. :)

> 
> pkg-config in Windows:
> 
> Try to download pkg-config already pre-compiled from somewhere like:
> http://ftp.gnome.org/pub/gnome/binaries/win32/dependencies/
> The rest is the same as in Linux, but the problem is: pkg-config needs some
> things set on path variables to detect the installed libraries and I couldn't
> get it to work, not even in Eclipse :(
Humm.. I don't know about pkg-config on windows, but was this needed or were the
README.win32 instructions enough for you to get it to compile correctly on windows ?

> 
> 
> I hope some of this actually helps someone...
It is, thanks for taking the time to write this email. I will use that to
improve the README so others don't have to go through it the hard way.

Thanks,
Youness.


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