Don't install GTK from source on Ubuntu.  Use the already-provided packages.  There are development packages available, find them.  Having gtk libraries installed for use is different from having them installed for development.  You should probably be looking for 'libgtk-3-dev', I believe, but I don't run Ubuntu 15.10 so I can't be positive.

@rogue.hackz & ArkPhase - I've been programming for 20 years, I started on the C88, with vi, on a console based bare bones 0.3 Red Hat. I was taught embedded systems design by a 30+ year senior embedded programmer for NASA. I see absolutely no point in using any of the flashy bullshit most n00bs use these days. The truth is, N00Bs have to use those plugins, and all those "extras", cause they are too busy being too new, to keep track of simple bullshit... If you are incapable of keeping track of your program's execution without needing "documentation", you're a n00b, if you can not deduce your mistakes without needing some "auto error finder", you're a n00b. More importantly, if you can not code in a manner, that is self-secured, and hard to exploit; you are a n00b. Period. So, in other words, you are kids... I am a kid.

Let's get the credentials out of the way, since they appear important.

I've been coding for roughly 27 years.  I'm a 'qualified expert'(meaning my aptitude has been tested and verified) in multiple languages and have taught/tutored several, especially C & C++.  I've done quite of a bit of embedded development on multiple platforms and have implemented code for systems run by NASA JPL as well as the United States Navy.  I have created custom hardware and written drivers for numerous devices.  I have assisted in the development of operating systems, kernels, bootloaders, system libraries, service daemons, and more.  I have been asked to edit more than one doctoral thesis and assisted with writing the firmware for an MIT robotics project.  I have even told genuinely humorous assembly jokes after half a bottle of jager in the middle of the woods with no computer nearby for miles.

Now for the shock & awe: I use so-called 'n00b' features.

I don't personally need it, but I do tend to make use of it when available and properly implemented.  Being well-versed or even highly proficient in a language and using features such as auto-completion, object browsers, class maps, flow monitors, etc. are not mutually exclusive.  I'll admit that I sometimes find myself fighting with auto-completion specifically when I find it to be less than adequately implemented but that does not mean that I do not find use for such features.  Typically, the speed at which usable, functional, efficient, and secure code can be written is improved when using such features.  This is true for 'n00bs' as well as for more experienced developers.

I also document my code.  I do this for multiple reasons, not the least of which is so that others can more easily understand my methods and reasoning.  I also use documentation to indicate the expected state of values at certain points in the code, to remind myself of interfaces, to denote future plans and intentions, and even to supplement the features provided by things like auto-completion.

I also attest to the capabilities of ArkPhaze.  ArkPhaze is one of the few people here from whom I accept critical criticism.  I respect ArkPhaze as a developer and hacker.  You should too.

More importantly; you should consider not just the words you speak(type) but also the wisdom(or lack thereof) behind the message that they provide.  One would expect someone of your supposed experience and proficiency to be more aware.

Actually, Mytosus's approach is valid, except that the "array to store the chars" should store pointers to char instead.  Given the base of an array, the index stored in the first array acts as an offset.  The first string will be at offset 0, the next at  *(baseAddressOfArray + arrayOfIndices[1]), then *(baseAddressOfArray + arrayOfIndices[2]), and so on.  The char* array can store pointers to these locations directly, effectively producing an array of C-style strings.

Can you be more specific about the message type?  Are you looking for an active connection between two clients or the ability to send a message to be read later(like via e-mail)?

PKI tends to work very well so I would strongly suggest looking into that.  If you're wanting to build the service yourself, there is plenty of documentation available.  If you're looking for an existing service, you may be able to locate one that uses PKI already.  You may also consider looking into I2P.

You're welcome.

+3 cookies for the amazingly important & useful information, thank you.

This is very unfortunate.  I would be interested in a list of all the companies that have been the cause for this drastic, but entirely necessary, action.  Those companies, and their actions, should be brought out into the spotlight for all to see.  What's more, I wouldn't be sad if their efforts were proven to be inadequate through a number of attacks that proved why grsec's standards are important.

I remember the call for copyright lawyers going out some time ago and checked with the lawyers that I knew at the time.  Unfortunately, they specialized in musical copyrights and despite my attempts to explain that software copyrights also fall under the realm 'artistic rights to license', they were unwilling to handle such a case.  Perhaps they knew what kind of assholes they'd be dealing with.

Although some of us will remain unaffected, for the most part, due to the fact that we port our own patches from testing or write our own patches from scratch, I expect this may have some far-reaching impacts that aren't easily predicted at this time.  I would not doubt that another project that claims to do similar work would pop up in the next couple of years.  I could see such a thing being started specifically to gain the interest of a number of people in the FOSS community and get new patches submitted by new people, effectively abusing a different subgroup for free work.  However, I also expect to see quite a few new 0days circulate in the next year or so.  Perhaps the latter will prompt the former; we shall see.

Update: it looks like VeriFone, producers a very popular credit/debit card processing system, are involved.

+1 cookie for determination.  Keep it up.  You can never learn too much(unless it's that your parents have a cam site).