Untangling the preprocessor

I found while working on my latest pet project that GCC pragmas and builtins were getting in the way of clean Doxygen parsing, for example, the following snippet would cause problems:

struct foo {
  struct bar yeah;
  char *woah;
  int wow;
} __attribute__((packed));

_Pragma("GCC diagnostic ignore -Wunused-parameter")
void foo(struct foo *f) {
  do_nothing_useful();
}

(Editors note: This is not production code… yet)

For future reference, Doxygen can easily be configured to ignore certain macros:

# ======================================
# Allow us to define our own list of
# macros to expand during preprocessing
# ======================================
ENABLE_PREPROCESSING   = YES
MACRO_EXPANSION        = YES
EXPAND_ONLY_PREDEF     = YES

# --------------------------------------
# A list of all of the macros to expand,
# in the form <macro>=<expansion>.
# --------------------------------------
PREDEFINED             = __attribute__(x)=
PREDEFINED            += _Pragma(x)=