Comment by DSMan195276 | Hacker News Reader

Comment by DSMan195276 | Hacker News Reader

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IMO, whether or not the C preprocessor is good depends on what you're trying to do and how you do it. I doubt there are any preprocessors or macro systems that can't be used to obfuscate code - That's basically the definition of what they do, modify your code before you compile it. Obviously, and strange/unexplained preprocessor usage should be examined and preferably removed.

The example you gave is not really fair though, because it seems pretty obvious to me that nobody ever looked at that code - it hardly matters they hid the backdoor in the the C pre-processor. If you take a look at the repo, it only has three commits - With the first one (https://github.com/alerj78/lucky7coin/commit/07d7e5fc53e5673...) being a supposed import of the code from the repo it used to exist in, and it's in this commit where the backdoor was inserted. The real issue is that people were running code from someone who appears to be a complete unknown, has no history for his code, and just assumed it was the same as the old code without checking.

Preprocessors are uniquely problematic in this regard, though, since they're just simple text-substitution engines. Things like templating (as in C++), in-language macros (as in Lisp variants), or language-level metaprogramming facilities (as in Ruby, Python, ...) all have access to actual entities in the language, which constrains their effects in a way that's safer and easier to reason about.

I'm not looking to deny that straight text-substitution has it's drawbacks, you're completely right. But that being said, I still don't see it as big of a deal as it seems. Generally speaking, bad/malicious pre-processor abuse like this sticks out like a sore thumb when you're reviewing code. If you don't have anybody reviewing the code then it doesn't really matter how you disguised it. At least with the C preprocessor, if there's something you're unsure about, you can run the preprocessor separately and look at the output, clearing up all doubt over what it does.

Also worth noting, one of the nicer things about the design of the C preprocessor is that it can be applied to a lot of different file-types. In more complicated low-level C projects, you can run the preprocessor over your C code, assembly code, linker scripts, etc.. which is a huge gain since you can have access to all your constants and simple macros, simplifying work and duplication. You can't get that with something tied to the language - Which is unfortunate, because like you said it's better to avoid the preprocessor, since writing things on the language-level makes them much easier to reason about.)

Even in Java – this is something next to no one knows – you can use metaprogramming and get the full AST, which you can then manipulate at will.

It seems to me that you could create something at least this devious using C++ templates and operator overloading. I wouldn't bet against it in the other languages you mention, either.

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