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Why can't code be uncompiled?
(lemmy.world)
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this post was submitted on 03 Jan 2024
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The long answer involves a lot of technical jargon, but the short answer is that the compilation process turns high level source code into something that the machine can read, and that process usually drops a lot of unneeded data and does some low-level optimization to make things more efficient during actual processing.
One can use a decompiler to take that machine code and attempt to turn it back into something human readable, but will usually be missing data on variable names, function calls, comments, etc. and include compiler-added optimizations which makes it nearly impossible to reconstruct the original code
It's sort of the code equivalent of putting a sentence into Google translate and then immediately translating it back to the original. You often end up with differences in word choice that give you a good general idea of intent, but it's impossible to know exactly which words were in the original sentence.
Thank you, sorry to push further but my understanding is that computers deal with binary so every language is compiled to machine code, which I took as binary.
So if the language has elements being removed and the machine doesn't need them shouldn't you get back out exactly what is needed to do the task? Like if you compiled some code and then uncompiled it you would get the most efficient version of it because the computer took what it needed, discarded the rest and gave it back to you?
Sorta, an optimizing compiler will always trim dead code which isn't needed, but it will also do things that are more efficient but make the code harder to understand like unrolling loops. e.g. you might have some code that says "for numbers 1-100 call some function" the compiler can look at this and say "let's just go ahead and insert 100 calls to that function with the specific number" so instead of a small loop you'll see a big block of function calls almost the same.
Other optimizations will similarly obfuscate the original programmers intent, and thinks like assertions are meant to be optimized out in production code so those won't appear in the de-compiled version of the sources.