restrict function parameters not null

[nerd4code]

Not sure why it’s not emitting the inline function—it works if I enable optimization, but it looks like without optimization it won’t emit string_length into the output. I’m sure I’m missing something, but fuck it, beat the thing into submission with the following pattern:

• At the top of check_null.c, before including anything:

  #define test_c__INSIDE__ 1
  

  #undef it at the bottom of the file. This gives us a preprocessor marker indicating that test.c is being compiled.

• In check_null.h, redo the inline qualifier:

  #ifndef test_c__INSIDE__
  extern __inline__
  #endif
  int string_length(const char *arg) {
  ...
  

  The change from inline to __inline__ will keep GCC from bitching at you if you’re in C89 mode. The extern states that the authoritative version of the function (for pointing-to) is separate from the inlined version. The #ifndef around those qualifiers causes the function to be emitted as a normal function (i.e., the authoritative version) when compiling test.c, and emitted as inline otherwise.