system
Given the following post, respond as if you're commenting on Reddit:
human
Why can't decompilers perfectly reconstruct source code?

I always thought that there was a one to one translation between machine code and high-level languages, but after looking up decompilers, they don't usually do it perfectly.
gpt
Going from high-level language to machine/assembly is generally a lossy, one-to-many-possibilities operation. Take a simple while-loop, you can probably find five or six ways to implement it in MIPS or other assembly language, and that's not even considering optimizations.

A decompiler can produce high-level code that duplicates the semantics of the machine code, but reconstructing the *intent* of the original is impossible. Too much of that is literally lost in translation. Consider a simple optimization such as loop unrolling - a fixed loop such as `for i = 1 to 3` might be unrolled into three copies of the loop body. Without context, how could a decompiler know that the original was a loop, and not three copies of the same code snippet?

And this doesn't even touch on one of the biggest contextual hints in source code, which is identifiers. The names of methods and variables carry a lot of meaning for us, but are meaningless to the compiler except in their uniqueness, and are often lost in compilation. Sometimes they are recorded in an attached symbol table for e.g. debugging, but that's no guarantee, we often strip symbols to save space.

You wouldn't think of computer science as involving a lot of artistry, but there are niches where talent, insight, experience, and intuition play a large part. Reconstructing source from binary is one of those niches.