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Syntax errors will be detected prior to runtime because the application will not be able to be compiled into whatever format it compiles down to (raw ASM, some

Syntax errors will be detected prior to runtime because the application will not be able to be compiled into whatever format it compiles down to (raw ASM, some IR, etc.). A fully AOT compiler will generally check more than a JIT compiler, but there is still compilation and it is still a "compiler" in a technical sense. And for the record, AOT languages also have "runtimes" provided by a platform. If someone combined gcc and glibc, would the combined product no longer be considered a "compiler"?

josteink 10y ago
It is my understanding that V8 provides you with the capability to interpret your code and run it, while gcc produces a resulting binary which be run independently of gcc. Can V8 be used to compile js to a artifact/binary which can later be executed independently of V8? If no, then it's not a compiler. It's as simple as that.
- cookiecaper 10y ago
  Executables from gcc can't be run independent of a binary-compatible C runtime. The difference is just that V8 includes the runtime and compiler in the same program. If they split it into v8c and v8lib without making any changes to the way that JavaScript is converted into something that your CPU processes, would it then be a "real compiler"? Are mcs or javac real compilers? They both leave behind an "executable", but they require a separate runtime to be installed actually execute it. What about GCJ? What about anything that compiles down to LLVM IR and depends on LLVM to convert it to machine code? Is that not a real compiler either? Is CPython a compiler? It leaves junk on my disk in the form of pyc files. I'm really curious why you insist that something isn't performing compilation if it doesn't write its output to disk. When is the process of compiling from one target into another not compilation? Perhaps you're suggesting that only compilers that emit appropriate machine code are "real compilers". That's silly, but I could understand if that's what you mean. However, I think you'll be disappointed to learn that V8 does directly emit machine code. [0] [0] https://github.com/v8/v8/tree/master/src/compiler https://github.com/v8/v8/tree/master/src/compiler
- slikts 10y ago
  There is no interpretation involved; V8 has an unoptimized base compiler for compiling JS to machine code one function at a time, and a pair of optimizing compilers that work based on runtime profiling. V8 also has a bytecode interpreter for low memory devices, but it'd mainly be used on very low end mobile devices.

josteink 10y ago

It is my understanding that V8 provides you with the capability to interpret your code and run it, while gcc produces a resulting binary which be run independently of gcc. Can V8 be used to compile js to a artifact/binary which can later be executed independently of V8? If no, then it's not a compiler. It's as simple as that.

cookiecaper 10y ago
Executables from gcc can't be run independent of a binary-compatible C runtime. The difference is just that V8 includes the runtime and compiler in the same program. If they split it into v8c and v8lib without making any changes to the way that JavaScript is converted into something that your CPU processes, would it then be a "real compiler"? Are mcs or javac real compilers? They both leave behind an "executable", but they require a separate runtime to be installed actually execute it. What about GCJ? What about anything that compiles down to LLVM IR and depends on LLVM to convert it to machine code? Is that not a real compiler either? Is CPython a compiler? It leaves junk on my disk in the form of pyc files. I'm really curious why you insist that something isn't performing compilation if it doesn't write its output to disk. When is the process of compiling from one target into another not compilation? Perhaps you're suggesting that only compilers that emit appropriate machine code are "real compilers". That's silly, but I could understand if that's what you mean. However, I think you'll be disappointed to learn that V8 does directly emit machine code. [0] [0] https://github.com/v8/v8/tree/master/src/compiler https://github.com/v8/v8/tree/master/src/compiler
slikts 10y ago
There is no interpretation involved; V8 has an unoptimized base compiler for compiling JS to machine code one function at a time, and a pair of optimizing compilers that work based on runtime profiling. V8 also has a bytecode interpreter for low memory devices, but it'd mainly be used on very low end mobile devices.