Paged Out #9 [pdf]

> Sorry, we moved this.

Isn't the borrow checker supposed to prevent these things? I was still holding an immutable reference.

Wait, you're getting blocked trying to download Paged Out!? This most likely is a problem with your ISP, not with the zine's server. Check with them first.

It's not standard conforming C. asm() is an extension.

What do you mean? It's just simple beginner's examples in C. Should be easy enough to understand, C is famously very simple ('portable assembler' as they say!).

I'll try to do the first one since I think it's the most illustrative:

  1  long typedef[[]]*($)(void*($),...);  
  2  int main() {  
  3   char* str = "Hello, world.";  
  4   $ $ asm("puts");  
  5   $:&&$&&$(str);  
  6  }

(1) is equivalent to "typedef long* $(void*, ...)". '$' is the name of the defined function type.

it's obfuscated as follows:

- typedef is a specifier and can go on either side of the type, same as int const/const int

- [[ ]] is an empty list of attributes

- "void*($)" is an argument named '$' of type void*, but parameter names are ignored in declarations.

- you can put parens in declarations since sometimes you need to group prefixes and postfixes in a different order

- dollar signs in names are allowed in many c compilers (and some other c-like languages)

- "..." are variadic arguments. puts doesn't have those, but the first argument uses the same register either way so it happens to work out in this case

(4) declares a function named '$' of type '$', shadowing the type, and links it to the assembly label "puts". calling $ calls puts.

normally it looks like `int call_foo(void) asm("foo");`

(5) is parsed as: "label $: address-of-label $ and function $ called on str. the address of a label is truthy, so the function also gets called.

unary && looks for the argument in the label namespace, but other operators don't, so the two dollars refer to different things.

that's about it. if you're familiar with the c standard and some common gnu extentions, you can deconstruct the examples into their basic elements easily enough