I'm trying to write my first game in c++, and I want it to dynamically load everything from files. This includes the enemies, and I was wondering if there was a way to dynamically include their code at runtime, instead of linking the on compile, so that the levels are easily interchangeable. Lua might be an option but I have no clue where to start, and dll seems to be Windows-only (and I wouldn't know where to start there anyway). Can anyone help with this?
tl;dr I want to link in code to my c++ game at runtime.
For the Lua approach you first need to choose the version first. Right now there is the major version 5.1 and 5.2. My previous work was using 5.1 and for my new project I decided to update to 5.2, however I found that my favorite script wrapping tool (SWIG) does not work with 5.2. Just something to decide at the beginning, because you do not want to get a version working and then have to change it.
Lua comes with makefile build environment. My first experience of trying to build on Windows was a bit of a nightmare, did not appear to just run out-of-the-box, so I opted to create my own Visual Studio project at the time, and just include all the .C files in the project. There are two files which need to selectively included/excluded depending on how you intend to compile: lua.c and luac.c. If you are planning to embed Lua in your app, then exclude both of these files; they both contain a main() function and are designed to build console apps. Include all the rest of the C files in your project.
You should be able to compile easy from this point.
When you include the headers of Lua, keep in mind that the functions are C functions so if you are including them from C++ you need to wrap the file inclusion inside of: extern "C" {} - example: C++ Lua 5.1 Issue
Wrapping your interfaces in another topic and there are lots of resources available. My favorite is SWIG but there are lots of options, including hand coding the conversion of your C/C++ -> LUA -> C/C++ code. Would recommend just focusing on getting the first part working first, get the interpreter embedded so that you can run a "hello, world!" script from Lua inside your app.
So going by your requirement of crossplatform use and dynamic linking, what you're probably looking for is an environment like QT which has QLibrary: https://stackoverflow.com/a/9675063/453673
But https://softwareengineering.stackexchange.com/questions/88685/why-arent-more-desktop-apps-written-with-qt
MingW is the open-source equivalent for Visual C++, so it can help you writing code for Windows (though if I had a choice, I'd directly use Visual C++). The way dll's are loaded in Windows is somewhat similar to the way they're loaded in Linux, so you'll be able to write code with #ifdef's to do conditional compilation. I've written one such program a couple of years back.
To load a shared library(always with .so as suffix) under Linux, you could use dlopen(), dlsym() and dlclose()
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I have an Objective-C based project with some C++ code. I have included library I want to use via CMake. However, Xcode autocompletion is not working properly for library's methods, classes and etc.
Despite that, project compiles and there are no errors during build after inputting some of the library classes or functions in code. Xcode can also correctly specify the error, if I miss something like required parameters for method call (It will show up build error, telling which parameter I forgot to use).
The problem is lack of autocompletion dramatically slows down the development and I need to fix it.
Considering the fact that Xcode is essentially just another UNIX make with GUI on top of it, I would advice just switching to VSCode because the C++ plugin there is designed to work with this kind of stuff.
In your case you could probably use some automatic cmake -> pbx generator if such tools even exist. Or, of course, do this manually, and configure the compilation out of an Xcode project.
I have some C++ code (exposing a C-only interface through a header) which I will use for an iOS project.
I can either create a static library and link to this from my app project, or add the source files directly to the app project - which option is best?
All answers appreciated!
Add the sources if you expect them to change often. Otherwise a library will be more suitable and will make your project cleaner (however, you will have to put only the header files in your project)
I've used OpenCV in one of my app projects which is mostly written in C++. I've found that adding the source files to the app project worked better for me because I made some minor changes to the code wherever appropriate. Comes down to the use case basically.
I always prefer to add the source if I have it, simply because it makes debugging easier. If you're making a call into a library routine and getting back an unexpected result (or crashing, or whatever), it's much easier to step into the library code with the debugger and figure out what's going on. If you just have a static library, it's a black box and you can't see what's going on inside. It also allows you to change the library code more easily if you encounter a bug or a missing feature (just be careful if the library is shared among other projects, to make sure you keep the library code up to date in its own repository).
Xcode is good about letting you keep your project organized, so use those features to your advantage. Keep the library code and headers separate from your main application and link it in as needed.
I suppose by code you don't mean a well formed library, so I expect this code could get any kind of modification pressure in the future. The best way is then wrapping it. here is one very nice example, but you might do it differently: http://robnapier.net/blog/wrapping-cppfinal-edition-759
I want to use simple plotting functions in my C++ code. Presently I am using Qt5 with VS2010 c++ compiler. I came across this library called koolplot. But I cannot buid it with VS2010 from its source files. I am opening vs2010 cmd and running nmake...It shows winbgim.h missing..I copied that header in MinGW include folder and ran it ...now it shows "Plotdata.h:warning: 'typedef' was ignored in this declaration" Please help...if any one knows a simple plotting library running with VS2010 please suggest..
According to its website, Koolplot is designed for the MinGW/gcc toolchain - you'll have to do a bit of leg work to get it to compile on Visual Studio, though I don't know specifically what you'd have to do without taking a closer look.
Also, the library seems to do its own window management and the like, so I'm not sure how well you'll be able to integrate it with Qt.
koolplot needs WinBGI library (BGI = Borland Graphics Interface?).
I have changed it to use native Win32 using VS2008:
http://www.tu-chemnitz.de/~heha/hs/koolplot-heha.zip/
It's still incomplete as a good Win32 implementation would implement koolplot in a DLL which self-registers a Window class, and has both C and C++ interface. Moreover, koolplot as-is doesn't support multiple scales, finer plotting options, GDIplus, and fast data update, so it's not the right thing to write an oscilloscope program.
It's C++ code is also outdated as there are lambda functions available now.
However, good integrating into Qt is another task.
how do I correctly implement Lua in a C++ program? I downloaded the Lua source, put the .c files in my src folder and the .h files in my include folder, included lua.h in my program's source code (with extern "C"{} of course) and hit "Build".
That's how all the tutorials tell me to use Lua with a C++ project.
But now I get the error "multiple definition of main" and some Symbols in the Lua code that could not be resolved. I understand what the first error means (conflict because Lua has a main and my program also has one), but how can I solve it?
Or did I understand something completely wrong about implementing Lua in a C++ program?
Check to make sure you didn't include luac.c, lua.c, and the source for any other programs that are included with Lua in with your source code. Lua's source includes a few extra utilities (i.e., luac), and chances are you've just included them in the project and forgotten to remove them, thus resulting in having more than one main.
In short, those are separate programs that you don't add to your project. If you can, just build Lua normally, link to the library, and include the header files as normal.
So, on the point of you misunderstanding how to use Lua, you probably did to some degree. It is entirely possible to just copy Lua's source into your code, though probably not advisable. What you really want to do is pull up the extracted Lua source in a terminal and build it. Then (according to Lua's INSTALL document), you'll want to type make platform, where you'll replace platform with whichever platform you're currently using (i.e., I'd use macosx, you might use linux, refer to the INSTALL for which platforms are supported). After that, it's up to you if you want to install it or not, but you'll just do make install (or sudo make install) to get that done.
After that, either add the appropriate linker flags when compiling to link to Lua (e.g., -llua) or alter your project's settings in your editor of choice to do roughly the same thing. That said, you'll want to refer to the INSTALL document provided with Lua for complete instructions on this.
I'm embedding Lua in my projects other way around, preferred way, IMO: compiled Lua as a static library.
Just comment the two main() blocks in Lua.c an Luac.c, then hit build and run again.
I made this on Lua 5.3.
I'm a total noob when it comes to linking and building with Visual Studio. I would like to integrate Lua into my C++ console application.
Can someone give a step by step on how to do this from getting the Lua dependencies from lua.org, to actually running a "Hello World from Lua" in VS, and all the steps in between.
Finding something like this online has been very difficult since most require prerequisite knowledge of building Lua and such.
Thanks :)
Start with the Lua for Windows package. It will get you a self-contained batteries included Lua installation. Lua for Windows is not an official distribution, but it is well respected by the Lua user community. You can use its lua.exe to gain experience with the language in a Windows environment, and its rich collection of tested extension modules is also available for use.
If you add its include and lib folders to your VS project configuration, you should be able to compile and link against Lua in short order.
One possible complication is that the LfW distribution is built against VC8's C runtime library. If that becomes a problem, then you can either compile Lua yourself as part of your Solution, or get a known good DLL that matches your specific version of Visual Studio from the Lua Binaries project.
Do remember that if you are using one of the distributed DLLs, it will have been compiled as C, and not C++. That means that you must wrap any references to the Lua include files in extern "C" {...} or you will have problems with linkage.
It really helps to have some experience with VS project configuration and building. In particular, experience with mixing C and C++ in a VS project is very helpful.
I heartily recommend following the advice already given about learning C and C++ and mixing the two together. Once you have that under your belt, you may want to check out LuaBind or LuaPlus for connecting C++ and Lua. You can do it manually (and you probably should, at first, to understand what's going on under the hood), but it's more efficient and cleaner, code-wise, to use one of those binding libraries. For debugging purposes, Decoda is a good choice; it can attach to processes started in VS which contain Lua code you want to check.