Polyglot Lua+C

[Hugo Musso Gualandi <hgualandi@...>]

I found a cool trick that I wanted to share... It is a short program 
that can be used by C and Lua at the same time. From the point of view 
of C it is as a header file you can #include. From the point of view of 
Lua, it is a module you can require(), which produces a string with the 
contents of said header file. I promise I have an excuse for why I did 
this!

   #define HACK \
   return [=[
       int foo() { return 42; }
   //]=]

How this works: In Lua, if the first line of the file starts with # 
then it is treated as a shebang line and skipped. In C, the backslash 
line continuation makes the second line be part of the `#define HACK` 
directive, which eats the opening [=[. The C99 comment at the end eats 
the closing ]=].

-- Hugo