问题
Is it possible to compile C++ program into some intermediate stage (similar to bytecode in java) where the output is platform independent and than later compile/link at runtime to run in native (platform dependent) code? If answer is no, why?
回答1:
It is indeed possible, see for example LLVM.
回答2:
Of course. Keep in mind that the C++ standard only specifies behavior: What should happen when this program executes. It doesn't specify how it should be implemented.
C++ code can be compiled to an intermediate format and JIT'ed to machine code, or it can be interpreted or anything else you like.
回答3:
This is trivial, and most compilers already do that. gcc compiles to RTL (register transfer language) which is then translated to the target CPU.
Similarly, managed C++ and C++/CLI are compiled to .NET.
Finally you can consider the Church Turing thesis that is a statement of equivalence of programming languages, so C++ can be compiled/translated to your favorite platform independent language (say, Perl, lisp, C--, etc).
回答4:
C++ source code (with some restrictions) is a platform-independent bytecode.
Why is it not?
Indeed, "bytecode" compilation procedure is then mere copying. The virtual machine that runs the "bytecode" is C++ compiler and a wrapper script. Yeah, it does some stuff that resembles compilation to machine code--but that's an implementation detail.
Here's a Linux implementation of such a "C++ virtual machine":
#/bin/sh
tmp=`mktemp`
g++ $1 -o $tmp && $tmp $2 $3 $4 ...
Does it answer the question? I think, it does. To the extent how specific the question is. Because it clearly explains theoretical possibility of compiling C++ into bytecode. Practical implementations also exist, for example, LLVM.
回答5:
Yes it is technically feasible. A bit of a plug for a former employer, but here's an implementation of exactly that: http://antixlabs.com/products/antixgamedevelopmentkit/. The packaging process is, roughly speaking, C/C++ -> (compiler) -> LLVM -> (backend) -> bespoke bytecode -> zip file. This is platform-independent. Once it's on the user's device the "player" converts bespoke bytecode -> (translator for that device) -> native elf file -> (loader/linker) -> fixed up code.
If the real question is, "does there exist any such industry-standard intermediate format which is widely supported on multiple platforms and suitable for all-purpose use, like Java bytecode?" then the answer is "no".
As for why, I'd say it's because there is no one organisation which has enough influence over C++ programmers, and no true necessity for Java-style deployment of C++ applications. Sun invented Java and a GUI library in one go, presented it to programmers, and didn't introduce the big proliferation of profiles until later.
C++ doesn't even have a standard GUI, and C++ environments are far more fragmented than Java. How do you tell a Windows app developer, a mobile phone developer, a smartcard implementer and a stock exchange backend implementer that they need to ditch their existing toolchain in favour of a platform-independent deployment mechanism for C++? They don't. And that's even before you get to the folks writing OSes and device drivers in C or C++ mixed with assembly. It's simply impossible to come up with a standard environment to support all of them.
回答6:
Parrot project will have c++ bytecode compilation and execution parrot Visual Studio can compile C++ as bytecode C++ managed
来源：https://stackoverflow.com/questions/1510989/can-c-be-compiled-into-platform-independent-code-why-not