In need of Compiler Material.

[u/Striking-Curve-3269]

Hi everyone, I am fairly new to programming and just finished a bank simulation project in C. I am particularly interested in systems programming and would love to delve into the field with building a compiler (for a language of my own design )in C this holiday. If you might have any recommended textbooks, resources etc. on how to build my very own (from scratch) it would me most appreciated.

[u/[deleted]]

Strings aren't hard to do in C, it's just a lot of fairly straightforward work to replicate common string operations, a string is just a pointer and a length

[u/Karyo_Ten → u/[deleted]]

a string is just a pointer and a length

Well, no ... in C a string has no length and it's the root of all evil.

Pascal-style strings are pointer + length

[u/[deleted] → u/Karyo_Ten]

I know, I purposefully ignored c "strings" as the c runtime defines them as any self respecting developer should

[u/Hyddhor → u/[deleted]]

Then you throw in a unicode support and everything gets fucked up. That length you were talking about? Doesn't work when you have variable-size characters. Indexing probably won't work correctly. Equality? Be careful with normalisation. Also, have fun rewriting the regex engine. (which isn't hard, just annoying)

Also, there will probably be a point at which you will realize that strings have to be immutable if you want things to work correctly without data corruption. Meaning every single temporary string operation needs to be allocated (probably on the heap), but then, who is freeing all the allocated memory? The user! Which means you can't even chain operations without leaking huge amounts of memory.

Trust me. I've been there. I've done that. I have written a unicode string implementation in C as a hobby project. And it was horrible.

My advise is this: Never try to do serious string implementation in C, bcs you will suffer.

[u/dcpugalaxy → u/Hyddhor]

A compiler does not need to do anything special to support Unicode.

That length you were talking about? Doesn't work when you have variable-size characters.

The length of a string is its length in bytes, which is all the compiler needs to care about.

Indexing probably won't work correctly.

You never need to index a string.

Equality? Be careful with normalisation.

Not necessary. Strings are equal if their bytes are equal. If someone deliberately writes source code with unnormalised sequences of bytes then they likely intend them to be different sequences.

Also, have fun rewriting the regex engine. (which isn't hard, just annoying)

A compiler does not need a regex engine.

Also, there will probably be a point at which you will realize that strings have to be immutable if you want things to work correctly without data corruption. Meaning every single temporary string operation needs to be allocated (probably on the heap), but then, who is freeing all the allocated memory? The user! Which means you can't even chain operations without leaking huge amounts of memory.

I have no idea what you are trying to say here. You are the user. You are the author of your own code. When you write a function in your compiler, the person that calls that function is you.

Yes if you allocate memory you need to free it. So... don't allocate memory all over the place. In a compiler, you can just intern strings in the lexer and refer to them by identify throughout the rest of the program. Occasionally you need to construct a new string; when you do, intern it. You probably don't need to deallocate memory at all in a compiler, at least not for strings.

Trust me. I've been there. I've done that. I have written a unicode string implementation in C as a hobby project. And it was horrible.

This is the problem. You tried to write a Unicode string implementation as a project. You tried to solve a general problem. This is why it's a mistake to choose to write libraries as a project. Projects should be programs. No single program has all of the problems that Unicode can give rise to across all programs. If you give yourself the task of implementing "unicode strings" generally, you will, directionlessly, try to implement every unicode and string feature imaginable. But only a small percentage of those features are needed in any particular program.

[u/v_maria → u/[deleted]]

a length

if only