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My question is a little bit stupid but I decided to ask advanced programmers like some of you. So I want to make a "dynamic" C++ program. My idea is to compile it and after compilation (maybe with scripting language like python) to change some how the code of the program. I know you will tell me that after the compilation I can not change the code but is there a way of doing that. Thank you!
You could design a modular architecture using plugins in external libraries. For example you could use the Command Pattern. That way you can dynamically load code that was generated after you main program. You would have to fix an interface though. Functions like GetProcAddress in the Windows api might be a good point to start.
For dynamic coding and rapid prototyping I recommend to have a look at Lua. The engine is very small and easy to integrate in your c++ program.
The only way to do that in C++ is to unload the DLL with the code to be
modified, modify the sources, invoke the compiler to regenerate the DLL,
and reload the DLL. It's very, very heavy weight, and it only works if
the compiler is present on the machines where the code is to be run.
(Usually the case under Unix, rarely the case with Windows.)
Interpreted languages like Python are considerably more dynamic; Python
has a built-in function to execute a string as Python code, for example.
If you need dynamically modifiable code, I'd suggest embedding Python in
your application, and using it for the dynamic parts.
Personally I have never played with re-compiling C++ during runtime, and I do not intend too. However I have been doing a lot of embedding of scripting languages lately.
Someone else mentioned the obvious first choice for embedding: Lua. Lua is a pretty popular language to embed and you will find a bunch of documentation about how to do it. Integrating it into the C++ will allow you to define behavior at runtime like you want.
What I am using is a wonderful langauge called Squirrel. It is a lot like Lua but with native object(class) support and C++-like syntax. I have managed to embed it into a C++ application, and through using the sqrat binding library both languages can share information easily.
I have squirrel building and initializing my UI. As a result, 0 compiling is required in order to craft and structure my UI for my game. I intend to take this a step further and use this gameplay-side in order to create similar behavior you are looking for(changing behavior at runtime through dynamic code usage)
I recommend Checking out squirrel here: http://www.squirrel-lang.org/
I plan on writing tutorials on how to embed squirrel and install the binding library, but I have not started on them yet. If I can remember, I will edit this post in the future (could be a few months) once I have completed them. In the meantime give it a shot yourself. You may find it to your liking.
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I'm getting a little rusty in scripting languages, provided they're popping like mushrooms lately :)
Today I thought that it would be nice to have a scripting language that talks seamlessly to C++, that is, could use C++ classes, and, the most important for me, could be compiled into C++ or some DLL/.SO (plus its .h) so that I could link it into my C++ program and make use of the classes the script defines or implements.
I know I could embed any popular scripting language such as lua, ruby, python... but the interface usually includes some kind of "eval" function that evaluates the provided scripting code. Depending on the tool used to couple C++ and the scripting language, the integration for callbacks of the script into C++ could be more or less easy to write, but I haven't seen any scripting language that actually allows me to write independent modules that are exposed as a .h and .so/dll to my program (maybe along the lines of a scripting language that generates C++ code).
Do you know any such tool/scripting language?
Thanks in advance.
PD. I've been thinking along the lines of Vala or Haskell's GHC. They generate C, but not C++...
UPDATE 2020: Today I would probably go with Lua + Sol2/3 except if I really want to avoid Lua as a language. Chaiscript becomes a good candidate in this case though it is not optimal performance-wise compared to Lua+Sol2/3 (though it was greatly improved through years so it is still good enough in many cases).
Falcon have been dead for some years, RIP.
The following ones are more C++ integration oriented than language bindings :
ChaiScript - trying at the moment in a little project, interesting, this one is MADE with C++ in mind and works by just including a header! Not sure if it's good for a big project yet but will see, try it to have some taste!
(not maintained anymore) Falcon - trying on a big project, excellent; it's not a "one include embed" as ChaiScript but it's because it's really flexible, and totally thought to be used in C++ (only C++ code in libs) - I've decided to stick with it for my biggest project that require a lot of scripting flexibility (comparable to ruby/python )
AngelScript - didn't try yet
GameMonkey - didn't try yet
Io - didn't try yet
For you, if you really want to write your scripting module in C++ and easily expose it to the scripting language, I would recommand going with Falcon. It's totally MADE in C++, all the modules/libraries are written that way.
The question usually asked in this context is: how do I expose my C++ classes so they can be instantiated from script? And the answer is often something like http://www.swig.org/
You're asking the opposite question and it sounds like you're complicating matters a bit. A scripting engine that produced .h files and .so files wouldn't really be a scripting engine - it would be a compiler! In which case you could use C++.
Scripting engines don't work like that. You pass them a script and some callbacks that provide a set of functions that can be called from the script, and the engine interprets the script.
Try lua: http://www.lua.org/
For using C++ classes in lua you can use:
To generate binding use tolua++: http://www.codenix.com/~tolua/
It takes a cleaned up header as input and outputs a c file that does the hard work. Easy, nice and a pleasure to work with.
For using Lua objects in C++ I'd take the approach of writing a generic Proxy object with methods like (field, setField, callMethod, methods, fields).
If you want a dll you could have the .lua as a resource (in Windows, I don't know what could be a suitable equivalent for Linux) and on your DllMain initialize your proxy object with the lua code.
The c++ code can then use the proxy object to call the lua code, with maybe a few introspection methods in the proxy to make this task easier.
You could just reuse the proxy object for every lua library you want to write, just changing the lua code provided to it.
This is slightly outside my area of expertise, but I'm willing to risk the downvotes. :-)
Boost::Python seems to be what you're looking for. It uses a bit of macro magic to do its stuff, but it does expose Python classes to C++ rather cleanly.
I'm the author of LikeMagic, a C++ binding library for the Io language. (I am not the author of Io.)
http://github.com/dennisferron/LikeMagic
One of my explicit goals with LikeMagic is complete and total C++ interoperability, in both directions. LikeMagic will marshal native Io types as C++ types (including converting between STL containers and Io's native List type) and it will represent C++ classes, methods, fields, and arrays within Io. You can even pass a block of Io code out of the Io environment and use it in C++ as a functor!!
Wrapping C++ types up for consumption in Io script is simple, quick and easy. Accessing script objects from C++ does require an "eval" function like you described, but the template based type conversion and marshaling makes it easy to access the result of executing a script string. And there is the aforementioned ability to turn Io block() objects into C++ functors.
Right now the project is still in the early stages, although it is fully operational. I still need to do things like document its build steps and dependencies, and it can only be built with gcc 4.4.1+ (not Microsoft Visual C++) because it uses C++0x features not yet supported in MSVC. However, it does fully support Linux and Windows, and a Mac port is planned.
Now the bad news: Making the scripts produce .h files and .so or .dll files callable from C++ would not only require a compiler (of a sort) but it would also have to be a JIT compiler. That's because (in many scripting languages, but most especially in Io) an object's methods and fields are not known until runtime - and in Io, methods can even be added and removed from live objects! At first I was going to say that the very fact that you're asking for this makes me wonder if perhaps you don't really understand what a dynamic language is. But I do believe in a way of design in which you first try to imagine the ideal or easiest possible way of doing something, and then work backwards from there to what is actually possible. And so I'll admit from an ease-of-use standpoint, what you describe sounds easier to use.
But while it's ideal, and just barely possible (using a script language with JIT compilation), it isn't very practical, so I'm still unsure if what you're asking for is what you really want. If the .h and .so/.dll files are JITted from the script, and the script changes, you'd need to recompile your C++ program to take advantage of the change! Doesn't that violate the main benefit of using script in the first place?
The only way it is practical would be if the interfaces defined the scripts do not change, and you just are making C++ wrappers for script functions. You'd end up having a lot of C++ functions like:
int get_foo() { return script.eval("get_foo()"); }
int get_bar() { return script.eval("get_bar()"); }
I will admit that's cleaner looking code from the point of view of the callers of the wrapper function. But if that's what you want, why not just use reflection in the scripting language and generate a .h file off of the method lists stored in the script objects? This kind of reflection can be easily done in Io. At some point I plan to integrate the OpenC++ source-to-source translator as a callable library from LikeMagic, which means you could even use a robust C++ code generator instead of writing out strings.
You can do this with Lua, but if you have a lot of classes you'll want a tool like SWIG or toLua++ to generate some of the glue code for you.
None of these tools will handle the unusual part of your problem, which is to have a .h file behind which is hidden a scripting language, and to have your C++ code call scripts without knowing that that are scripts. To accomplish this, you will have to do the following:
Write the glue code yourself. (For Lua, this is relatively easy, until you get into classes, whereupon it's not so easy, which is why tools like SWIG and toLua++ exist.)
Hide behind the interface some kind of global state of the scripting interpreter.
Supposing you have multiple .h files that each are implemented using scripts, you have to decide which ones share state in the scripting language and which ones use separate scripting states. (What you basically have is a VM for the scripting language, and the extremes are (a) all .h files use the same VM in common and (b) each .h file has its own separate, isolated VM. Other choices are more complicated.)
If you decide to do this yourself, writing the glue code to turn Lua tables into C++ classes (so that Lua code looks like C++ to the rest of the program) is fairly straightforward. Going in the other direction, where you wrap your C++ in Lua (so that C++ objects look to the scripts like Lua values) is a big pain in the ass.
No matter what you do, you have some work ahead of you.
Google's V8 engine is written in C++, I expect you might be able to integrate it into a project. They talk about doing that in this article.
Good question, I have often thought about this myself, but alas there is no easy solution to this kind of thing. If you are on Windows (I guess not), then you could achieve something like this by creating COM components in C++ and VB (considering that as a scripting language). The talking happens through COM interfaces, which is a nice way to interop between disparate languages. Same holds for .NET based languages which can interop between themselves.
I too am eager to know if something like this exists for C++, preferably open source.
You might check into embedding Guile (a scheme interpreter) or V8 (Google's javascript interpreter - used in Chrome - which is written in C++).
Try the Ring programming language
http://ring-lang.net
(1) Extension using the C/C++ languages
https://en.wikibooks.org/wiki/Ring/Lessons/Extension_using_the_C/C%2B%2B_languages
(2) Embedding Ring Interpreter in C/C++ Programs
https://en.wikibooks.org/wiki/Ring/Lessons/Embedding_Ring_Interpreter_in_C/C%2B%2B_Programs
(3) Code Generator for wrapping C/C++ Libraries
https://en.wikibooks.org/wiki/Ring/Lessons/Code_Generator_for_wrapping_C/C%2B%2B_Libraries
This may seem a trivial question, but it's one that's bothered me a lot lately. Why do some programmers refer to "C++/STL" like it's a different language? The STL is part of the C++ standard library -- and therefore is part of the language, "C++". It's not a separate component, and it does not live alone in the scope of things C++. Yet some continually act like it's a different language altogether. Why?
It's possible to be a competent and experienced C++ programmer and never use the STL. You may be using Boost or ACE, or been an MFC windows programmer for 10 years.
If you want someone experienced in using the STL, asking for someone who knows C++ is no guarantee that you'll get one.
Also for my mind, writing code that's heavily dependent on the STL feels very different to writing, say, MFC code. They might as well be different languages. They certainly won't look particularly similar.
An understanding of the STL isn't necessary to understand C++. It's useful to have when you need ADTs, but you can go (could have gone?) through your whole C++ career without needing it.
The above answers are really good; I'm only going to add to their content in a broader context.
Developers might refer to language/api|library e.g. C/Win32, Java/Struts, Java/Spring, C#/.net MVC because there are in essence two knowledge bases - knowledge of the language in question and knowledge of how to use that specific library, API or framework. Something like Win32 is pretty huge, as is say Django, which I'm currently learning. Django itself works in a very specific way and knowing that is what I'm learning, not Python.
The same is true of C++/MFC or C++/Boost or C++/STL. The language is C++ - the API/library you're using is MFC, Boost or STL.
Probably because STL came a little late to the C++ game, and many people have written code that does not use any STL. For example, think early win32 programming with MFC.
Guess:
When C++ was first released, the STL did not exist. It came into existence later as an optional addition and then was incorporated into the standard.
When writing a resume, people would often list C/C++ as a language, which, in many cases means they don't know either.
Sometime resumes would list "Visual C++" as a language, trying to indicate they don't know what a language is.
This, together with "great knowledge of C++ and PHP" statements, go strait into recycle bin at my firm. Not because they are necessarily bad programmers - but because the interview time waste is not worth it.
I'm looking to be able to build GUI applications quickly and painlessly as possible. I'm competent (though not expert, and have no formal training) in C++, but have never used a GUI building toolkit or framework or anything. I am not a professional programmer and am totally inexperienced and ignorant when it comes to building GUI apps. Have spent hours researching trying to figure out what to do; only getting more confused and discouraged though.
Qt and wxWidgets seem like the most popular options for cross-platform apps, though cross-platform isn't necessarily all that important to me; Windows-only is fine if that means the fastest learning curve.
Qt seems cool and the Qt Creator is sweet looking with lots of good demos, except it has its own classes for everything, and I'm not overly keen on learning a bunch of stuff that's only applicable to the Qt platform itself rather than more generally. I suppose I could avoid using the Qt classes except for the GUI stuff where I have to use them, but I have no idea how wise or unwise that would be.
I was thinking Visual Studio would have the smallest learning curve, but when I open a test GUI app, I see a bunch of foreign looking stuff like carats (^) all over the place - I found online that these mean "handles", which I have trouble even understanding the definition or purpose of ("sort of like pointers but not really" is basically how I've read people define them).
I know pretty much nothing about wxWidgets, or how it compares with Qt.
So every option has a big learning curve - and ideally I'd like to know which one minimizes the time you have to spend learning the toolkit/framework itself. Since I'm likely never going to be making money from the programs I create, the time I spend learning a specific toolkit would be pretty costly. I just want to be able to make a functional program using the C++ knowledge I have, but in GUI form. At the moment it seems if I want to make a GUI app, I'd have to spend way more time learning the GUI framework I'd use than writing the functional part of the app itself.
Any input from people wiser and more experienced than me would be appreciated :)
First and foremost, start simple. There's a lot to the subject. If you are finding it hard, don't try and take it in all at once.
Most of the good GUI packages have tutorials. The best advice I can give is that you try each of them, or at least a couple of them. They are the best short introduction you can have to the library you choose and if they are any good they narrow down what you need to absorb at first. That will give you some basis for comparison, because they are each trying to do very similar things (and you will see some of them before you are done), but they have different feels. You will likely find you have a preference for one and that's the one to get serious with. It will also give you a sense of what's hard about GUI programming as separate from the particulars of one package, which, if you have only used one, you won't have seen. Personally I find this sort of knowledge very helpful, because it makes me less intimidated by particulars.
Here's a list of tutorials in one place, though you have likely seen them already:
Qt's tutorial
WxWidgets' tutorial
Gtkmm book. Not quite a tutorial, though there are lots of examples.
.NET tutorials, either for WinForms or for WPF.
Second, it sounds to me that you need to get some in depth understanding of the concepts of GUI programming, not just a particular library. Here there is no substitute for a book. I don't know all of them by a long shot, but the best of the bunch will not just teach you the details of a toolkit, they will teach you general concepts and how to use them. Here are some lists to start with though (and once you have titles, Amazon and Stack Overflow will help to pick one):
List of Qt books
WxWidgets book (PDF version)
There are tons of WPF and WinForms books. I can't make a good recommendation here unfortunately.
Third, take advantage of the design tools (Qt Creator, VS's form building and so on). Don't start by trying to read through all the code they generate: get your own small programs running first. Otherwise it's too hard to know what matters for a basic program and what doesn't. The details get lost. Once you've got the basics down though, Do use them as references to learn how to do specific effects. If you can get something to work in the design tools, then you can look at particular code they generate to be able to try on your own hand-written programs. They are very useful for intermediate learning.
I'm not overly keen on learning a bunch of stuff that's only applicable to the Qt platform itself rather than more generally.
I second the comment of GRB here: Don't worry about this. You are going to need to learn a lot specific to the toolkit no matter which toolkit you use. But you will also learn a lot that's general to GUI programming with any of the decent toolkits, because they are going to have to cover a lot of the same ground. Layouts, events, interaction between widgets/controls, understanding timers -- these will come up in any GUI toolkit you use.
However do be aware that any serious GUI package is an investment of time. You will have a much easier time learning a second package if you decide to pick one up, but every large library has its personality and much of your time will be spent learning its quirks. That is, I think, a given in dealing with any complex subject.
I suppose I could avoid using the Qt classes except for the GUI stuff where I have to use them, but I have no idea how wise or unwise that would be.
You do not need most of the non-GUI classes of Qt to use Qt's GUI properly. There are a handful of exceptions (like QVariant) which you'll need just because the GUI classes use them. I found you can learn those on a case-by-case basis.
Which is the easiest to learn is really going to depend on how you personally learn.
Personally, I've found Qt to be the easiest to learn so far. The GUI classes are rather nice to use, but I've found the non-GUI classes to be excellent, making it easy to avoid a lot of common issues you'd normally get with a more basic API. The documentation is excellent, IMO, as are the books, the examples, etc. It's also being very actively developed, with a few new technologies coming in the near future (like DeclarativeUI).
I've found Visual Studio/Windows API/.Net to be a good bit more complicated to learn. The API documentation on MSDN is rather complicated and not really organized in a manner that I find intuitive.
I've tried learning WxWidgets a few times, but I've never liked the API documentation.
All this is just my personal experience, YMMV of course. I'd say just dabble in all of them and see which one takes you the furthest, it won't hurt to try multiple.
As a person who learned C++ through Qt, I can only say that they work very well together. C++ purists (like I have become) will find lots of things in Qt not to their liking (the moc preprocessor, e.g., and the continued absence of exceptions for error reporting), but looking back, Qt provided a very gentle introduction to C++ for me.
And if you're like me, you throw in a handful of boost libs in each Qt project, because we want to write "real" C++, not the softened thing Qt uses :)
I would suggest wxWidgets. To me, it's pretty intuitive and looks nice.
Code::Blocks was built with it, so check that out to see if you like the graphics.
There are also a slew of bindings for wxWidgets, such as wxPython, wxErlang, and others, so if you decide to switch off of C++, you can take wxWidgets with you.
I also use wxWidgets and use it all the time for Windows-only applications (the only downside is that wxWidgets is notorious for large .exe filesizes, which may or may not be a problem for you). I found it very simple to use from the start, especially when combined with a GUI designer (personally I use wxDev-C++).
I've never used Qt, so I can't speak to its simplicity, but I doubt the difficulty is on a vastly different scale than that of wxWidgets. However, what I can say is that no matter what API you use (wxWidgets, Qt, WinAPI, etc) your code will be "locked into" that particular platform, so don't worry if you feel that learning Qt will lock you into the Qt platform (because the same thing will happen with any of those APIs).
If you're working solely on Windows however, you may want to do a few simple programs with WinAPI first. That way you have a basic understanding of the lowest level of Windows GUI programming before you move onto Qt/wxWidgets. That said, if you're really into cross-platform programming, then don't worry about that and go straight into Qt/wxWidgets.
I can't intelligently comment on the learning curve aspect, but a quick survey of StackOverflow questions shows about twice as many Visual C++ questions as Qt questions. Probably means that there is a larger support group in place for Visual C++. Might make learning it a little easier if there are more folks to help out.
No matter what you pick, I am quite sure it won't be easy and painless.
Having said that, I know that in some schools they use FLTK because they consider it relativelly easy to learn. I have never tried it.
In my everyday work I use WTL which is as close to the system as it gets while still providing some level of abstraction over pure Win32. I am not sure if I would consider it easy to learn, though, especially given the lack of documentation.
I recommend codegear C++ builder (previously known as borland C++ builder) from codegear which comes with a 30 trial. The nicest thing about it is that the GUI provides you with components that you drop onto a form in a WYSIWYG fashion and make functional by adding code to handle the events it fires. It comes with a whole bunch of compontents out of the box and you can add 3rd party components to it too, like the awesome ExpressQuantumGrid from devexpress, or write your own. It's very powerfull if you know what you're doing but intuitive enough that a beginner can write a database CRUD application in about 20 lines of very simple code.
Since nobody has mentioned it yet, for the sake of completeness, have a plug for the Fox toolkit. This is the one I used last time I did any C++ UI work of my own volition. There are also binding for this to Ruby and Python (the latter being many years out of date, though).
In general, the choice of a toolkit for self-directed work comes down to personal preferences for
the layout manager style
the event handler registration style
How native the widget set looks/can be made to look
If cross-platforming is not necessary, try .net + msvs or delphi. easy, all-in-one, no pain.
Qt is the best option for you. It's the easiest to learn, the most elegant and powerful and it is completely free.
Visual C++: This is an IDE, but it comes with its own GUI library called MFC. MFC is an old library with many quirks and it is difficult to learn and use. Many C++ programmers use it on Windows because it comes from MS, it's fast and it's free if you buy Visual C++. Since VC++ is an IDE, you can also use wxWidgets and Qt with it, although in your particular case I would recommend Qt Creator instead.
You seem to have experimented with Managed C++. Don't use that, even MS recommends that you only use Managed C++ as glue between C++ and C#.
wxWidgets: This one was a strong contender up to the day when Qt became free for commercial projects. It was always in the shadow of Qt and it is known that the documentation is not very good and the API is not as easy to learn as Qt's. Cross-platform MFC would be a good way to describe it.
C++ Builder: Borland made too many mistakes with C++ Builder and ended up getting out of the dev tools business altogether. It was a good product and I originally learned Windows GUI programming in one of the first versions, but I won't use it any more. There are better options and it is too expensive.
I want to move various parts of my app into simple scripts, to allow people that do not have a strong knowledge of c++ to be able to edit and implement various features.
Because it's a real time app, I need to have some kind of multitasking for these scripts. Ideally I want it so that the c++ app calls a script function which then continues running (under the c++ thread) until either a pause point (Wait(x)), or it returns. In the case of it waiting the state needs to be saved ready for the script to be restarted the next time the app loops after the duration has expired.
The scripts also need to be able to call c++ class methods, ideally using the c++ classes rather than plain wrapper functions around c++ classes.
I don't want to spend a massive amount of time implementing this, so using an existing scripting language is preferred to writing my own. I heard that Python and Lua can be integrated into a c++ app, but I do not know how to do this to achieve my goals.
The scripts must be able to call c++ functions
The scripts must be able to "pause" when certain functions are called (eg. Wait), and be restarted again by the c++ thread
Needs to be fast -- this is for a real time app and there could potentially be a lot of scripts running.
I can probably roll the multitasking code fairly easily, provided the scripts can be saved and restarted (possibly by a different thread to the original).
You can use either Lua or Python. Lua is more "lightweight" than python. It's got a smaller memory footprint than python does and in our experience was easier to integrate (people's mileage on this point might vary). It can support a bunch of scripts running simultaneously. Lua, at least, supports stopping/starting threads in the manner you desire.
Boost.python is nice, but in my (limited) experience, it was difficult for us to get compiling for our different environments and was pretty heavyweight. It has (in my opinion) the disadvantage of requiring Boost. For some, that might not be a problem, but if you don't need Boost (or are not using it), you are introducing a ton of code to get Boost.python working. YMMV.
We have built Lua into apps on multiple platforms (win32, Xbox360 and PS3). I believe that it will work on x64. The suggestion to use Luabind is good. We wound up writing our own interface between the two and while not too complicated, having that glue code will save you a lot of time and perhaps aggravation.
With either solution though, debugging can be a pain. We currently have no good solution for debugging Lua scripts that are embedded into our app. Since we haven't used python in our apps I can't speak to what tools might be available there, but a couple of years ago the landscape was roughly the same -- poor debugging. Having scripting to extend functionality is nice, but bugs in the scripts can cause problems and might be difficult to locate.
The Lua code itself is kind of messy to work with if you need to make changes there. We have seen bugs in the Lua codebase itself that were hard to track down. I suspect that Boost::Python might have similar problems.
And with any scripting language, it's not necessarily a solution for "non-programmers" to extend functionality. It might seem like it, but you will likely wind up spending a fair amount of time either debugging scripts or even perhaps Lua.
That all said, we've been very happy with Lua and have shipped it in two games. We currently have no plans to move away from the language. All in all, we've found it better than other alternatives that were available a couple of years ago. Python (and IronPython) are other choices, but based on experience, they seem more heavy handed than Lua. I'd love to hear about other experiences there though.
I can highly recommend that you take a look at Luabind. It makes it very simple to integrate Lua in your C++ code and vice versa. It is also possible to expose whole C++ classes to be used in Lua.
Your best bet is to embed either lua (www.lua.org) or python (www.python.org). Both are used in the game industry and both access extern "C" functions relatively easily with lua having an edge here (because data types are easier to translate between lua and C). Interfacing to C++ objects will be a bit more work on your end, but you can look up how to do this on Google, or on lua or python discussion forums.
I hope that helps!
You can definitely do what you want with Python. Here are the docs on embedding Python into an application. I'm pretty sure Lua would work too, I'm just less familiar with it.
You're describing cooperative multi-tasking, where the script needs to call a Break or Wait function periodically. Perhaps a better solution would be to run the scripting language in its own thread, and then use mutexes or lock-free queues for the interfaces between the scripting language and the rest of your program. That way a buggy script that doesn't call Break() often enough can't accidentally freeze your program.
Take a look at the Boost.Python library. It looks like it should be fairly straightforward to do what you want.
Take a look at SWIG. I've used it to interface with Python, but it supports many other languages.
One more vote for Lua. It's small, it's fast, it doesnt consume much memory (for games your best bet is to allocate big buffer at the initialization and re-direct all Lua memory allocations there). We used tolua to generate bindings, but there are other options, most of them much smaller/easier to use (IMO) than boost.python.
As for debugging Lua (if you go that route), I have been using DeCoda, and it has not been bad. It pretends to be an IDE, but sorta fails at that, but you can attach The debugging process to visual studio, and go down the call stack at break points. Very handy for Tracking down that bug.
You can also embed C/C++ scripts using Ch. I've been using it for a game project I'm working on, and it does well. Nice blend of power and adaptability.