Recently, I've started working with OpenGL using C++.
I'm annoyed by the way of declaring Vertex or changing current Color
the glColor3f() and glVertex{2,3,4}{sdif}() methods.
now then, why OpenGL don't overload those functions.
for instance, it will be better to type glColor() and glVertex() and they will be recognized by the number of parameters and their type.
eventually, the code will look much better and easier to read, with the same results.
I hope there's a good reason to not overload similar functions.
Because OpenGL was originally designed with C as the primary language for its API, and C doesn't support function overloading.
However, quoting from Wikipedia:
Although the function definitions are superficially similar to those
of the C programming language, they are language-independent.
It is always possible for OpenGL to have a C++ interface that supports function overloading and all the good stuff, though AFAIK there aren't any specification on that, and are mostly supported only with C++ wrappers.
Related
Where I can find C++ specification for Vulkan (same like the official C one on Khornos pages), describing the particular Vulkan api primitives and functions? Does it even exist (I was trying to find it with no success)?
Personaly I am using the C api even with C++ as I already got used to its style and it fits my needs perfectly (verbose, but you see everything), but I have to go through the code written by other people using C++ api. Usually Vulkan C++ api is just some syntactic sugar build upon the C api function calls, but sometimes digging through vulkan.hpp and trying to figure out what is going on is really annoying.
I am aware of this: https://github.com/KhronosGroup/Vulkan-Hpp
There is no "Vulkan C++ specification". There's a header file containing some functions and types that make using Vulkan more C++-friendly. But those are not part of any actual specification.
The mapping from "VulkanHpp" into regular C Vulkan is pretty obvious in most cases and can be deduced just from the nature of the APIs in question. vk::ImageCreateInfo means the same thing, with the same fields, as VkImageCreateInfo as defined by the Vulkan specification. The C++ wrapper is not trying to confuse users as to how it works.
While developing a new product, we decided to go for a mix of C++ and C#, haven been told that bridging them to allow the C# code to call the C++ code would be easy (spoiler, it's not).
We're pretty experienced C++ programmers and not at all C# programmers so we pretty much just had to believe what we've read. A few attempts to call C and Objective-C was promising and we even found a few articles that showed how to make an unmanaged C++ class available in C# -- or at least we thought. The C++ code in the articles, wasn't C++, but instead the horrible monster C++/CLI that Microsoft seems to think is C++. Since we're doing the C# stuff to get some bits "for free" in macOS and Windows, C++/CLI isn't an option either :-(.
Anyway, plenty of people have claimed that it's easy to call C++ code from some specific programming language, but so far, I haven't seen a single one that will allow me to do so (I haven't been paying too much attention to this, so please provide me with an obvious example). C++ invariably always means C with no C++ stuff at all; no namespaces, classes, no stl, lambdas or anything. Just plain dumb C.
So, are there any languages, besides C++(/CLI) that will allow me to do the following:
Create an instance of a class, using a C++ constructor, and dispatch it with a C++ destructor.
Call member functions on an object ( foo f; f.foo();) with a C++ class.
Use std::vector, std::find_if, std::string and other stuff from the stl. Complete coverage of the stl is not required.
Use overloaded functions (i.e. f(), f(int), f(std::string))
Use overloaded operators (foo operator + (foo, foo))
Use C++11, C++14 and/or C++17 features.
Use RAII (rather important IMHO).
Use namespaces.
No. There is no such language.
Unless you count Objective-C++. But that falls pretty much in the same bucket as C++/CLI, in being C++ with some extensions. And C++/CX is another such beast.
There are some interop tools that can work with C++ classes (SWIG for example), but I have never heard of a tool that is capable of instantiating C++ templates (like vector or find_if) on demand.
What languages will call C++ with no explicit bridging?
The short answer to this question is: NONE
Remember that a programming language is a specification written in some technical report, usually in English. For examples, read n1570 (the spec of C11) or R5RS (the spec of Scheme). For C++, see n3337.
Actually, you are interested in implementations, e.g. in compilers and interpreters for your programming languages. These implementations are practically software. And then the answer might become: it depends (notably on the ABI used & targetted by your compiler and system).
See for examples this list of ABIs for Linux.
plenty of people have claimed that it's easy to call C++ code from some specific programming language,
The C calling conventions are quite common, and it might help to declare every C++ function callable from outside as extern "C". But there is no silver bullet, and details matter a lot.
So, are there any languages, besides C++(/CLI) that will allow me to do the following:
list of C++ features skipped
Probably not.
You probably need at least to understand more about memory management approaches. I recommend understanding more about garbage collection, e.g. by reading the GC handbook (at least for underlying concepts & terminology). Learn more about foreign function interfaces (in some cases, the libffi might help) and language bindings.
You might also consider generating some of the C++ or C glue code, maybe with SWIG (or write your own C++ glue code generator).
On operating systems providing dynamic linking capable of loading plugins at runtime (e.g. Linux with dlopen(3)/dlsym(3); but other OSes often have similar facilities) you could even consider generating some C or C++ glue code at runtime in some temporary file, compile it as a temporary plugin, and dynamically loading that plugin. You could also consider JIT-compiling libraries like GCCJIT or LLVM (or libjit).
I recommend reading SICP, the Dragon Book, and probably Lisp In Small Pieces. Of course, learn something about OSes, e.g. Operating Systems: Three Easy Pieces. Reading about Linkers and Loaders could also help.
As an excellent example of cleverly gluing C++, look into CLASP and see this video.
But whatever approach you take, you'll need a lot of work (years, not weeks).
C++ as a language does not have a defined ABI (Application Binary Interface) - which basically means that there is no universal standard of what a C++ class/function call/template would look like in binary form on any given platform, or across platforms.
What that means is that there is no universal way to call C++ code from other languages, on different platforms, or even across compilers on the same platform. It also means that the people who are telling you "it's easy to call C++ code from XYZ language" are mostly incorrect (or at least incredibly incomplete).
Where there are interfaces it's either because the provider of the interface controls the ABI (C++/CLI with .NET), or because there is a translation layer from C++ to something like the C calling convention (Boost::python).
Some work has been done towards attempting to define an ABI per-platform (http://open-std.org/JTC1/SC22/WG21/docs/papers/2014/n4028.pdf), but as far as I'm aware it has not yet been accepted into C++17.
You can look into using C++ interpreter, which allows for the fine-grained control you ask for. But I don't know of any that "just works", see also:
Have you used any of the C++ interpreters (not compilers)?
I am currently working on a Source-to-source compiler that transforms code wirtten in an OpenCL superset to "ordinary" OpenCL. I would really like to use clang as a library to parse and analyze the source code. Especially, I really need all the available type information and I would like to have an AST to make use of clang's Rewrite capabilities.
Fortunately, the OpenCL superset that needs to be parsed is really a "mixture" between OpenCL and C++, i.e. the code is basically OpenCL extended with some C++ stuff. In detail, there are possibly template annotations before a function definition and there may be structs containing methods (including operator definitions).
I was hoping that I can use clang to parse this language, since the clang parser is capable of parsing all these constructs. However, I am not sure how (if possible) to tell clang to parse OpenCL and C++ constructs at once. If possible, I really want to avoid touching the clang code base, but I would prefer using clang as a library instead. Maybe it is possible to setup an appropriate instance of clang's LangOptions class that tells clang to parse all these constructs?
Any ideas on how to make clang parse this mixture between OpenCL and C++? Any help is appreciated, and thanks in advance!
You're trying to mix two different front ends, involving both parsing and name resolution.
I think you are in for a rough trip. The key problem is you are trying to glue together things that had no effort expended, to make them gluable. This usually leads to integration hell. You don't see people doing this with Fortran and C++ for the same reasons.
To start with, you'll discover you will have to define the semantics of how the C++ extensions interact with those of OpenCL. If you check out the C++ standard, you'll discover 600 pages of results from committee arguments on how C++ interacts with itself. So unless you can define a radically simple interaction, you'll have a tough time knowing what your mixed OpenCL/C++ program means.
Your second problem will be interleaving the Clang parsing machinery for C++ (AFAIK hand written code) with the Clang parsing machinery for OpenCL (don't know anything about it, but assumed it follows the C++ style). There's no obviously good reason to believe you can just pick and choose these to interleave easily. It may work out fine; just not a bet I'd care to make.
The next place you are likely to have trouble is in building an AST for the joint language. Maybe it is the case that Clang has defined AST nodes for both C++ and OpenCL in a way that easily composes to a joint Clang/OpenCL tree. Since the node types are chosen by hand, and there was no specific reason to design them to work together, it is also not obvious they will compose nicely.
Your last task, given a "valid" OpenCL/C++ tree, to transform it to OpenCL. How in fact will you expand a C++ template (or any general C++ code) to OpenCL code?
[Check my bio for another system, DMS, that might be a bit better for this task; it provides uniform infrastructure for multiple languages that would make some of this easier. Somewhat similar to what you are trying to do, we have used DMS to mix C++ with F90 and APL concepts for easy expression of vector operations in a prototype Vector C++, but we did not try to preserve F90 and APL syntax and semantics exactly for all the above reasons].
It isn't my purpose to rain on your parade; progress is made by the unreasonable man. Just be sure you understand how big a task you are taking on.
I am choosing a GUI toolkit for C++ to learn. I have done some searching online and most people suggest GTKmm for C++ over GTK+. Despite that fact, I have seen some C++ applications made using GTK+.
Therefore, I just want to know the specific reasons for this:
1. Why GTKmm is preferred for C++?
2. What are the limitations I will face if I use GTK+ for C++ applications instead of GTKmm?
gtkmm allows you to write code using normal C++ techniques such as encapsulation, derivation, and polymorphism. As a C++ programmer you probably already realize that this leads to clearer and better organised code.
gtkmm is more type-safe, so the compiler can detect errors that would only be detected at run time when using C. This use of specific types also makes the API clearer because you can see what types should be used just by looking at a method's declaration.
Inheritance can be used to derive new widgets. The derivation of new widgets in GTK+ C code is so complicated and error prone that almost no C coders do it. As a C++ developer you know that derivation is an essential Object Orientated technique.
Member instances can be used, simplifying memory management. All GTK+ C widgets are dealt with by use of pointers. As a C++ coder you know that pointers should be avoided where possible.
Less code. The GTK+ C object model uses prefixed function names and cast macros. For instance: gtk_button_set_text(GTK_BUTTON(button), "sometext"); gtkmm C++ code is shorter and clearer. For instance: button.set_text("sometext");
There's no need to worry about GTK+'s inconsistent reference-counting policy.
Source: http://live.gnome.org/gtkmm/FAQ
I have often seen the spinning gears OpenGL example ( I think originally done by SGI) but I today I have only been able to find C and Ruby implementations, can anyone point me to a c++ implementation?
What, in particular, would you be looking for in a C++ implementation that the C one doesn't provide? OpenGL is a C API, and thus a C demonstration is practical. A C++ implementation would call all the same functions in the same order and to the same effect, it would likely just wrap the implementation in an object. This doesn't really further one's understanding of the core API, and can possibly add a layer of obfuscation to those not familiar with some C++ styles and patterns.
If what you are really looking for is an example of initiating OpenGL wrapped in a C++ framework, I made a few of those a while back. You can find them here. Please note that I'm no longer actively maintaining the code or page, though.
If you want to mess around with OpenGL i strongly reccomend using OpenSceneGraph (OSG) since you can focus better on computer graphics aspects instead. It's using all the C++ magic and design patterns.