Paged Out #9 [pdf]

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

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

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