__attribute__

[ghazel]

It might be ambitious, but I'm trying to parse /usr/include/math.h (on OS X)

Here's what I have so far:

f = '/usr/include/math.h'
prep = C::Preprocessor.new
# XXX: bug #4
prep.pwd = File.expand_path('.')
source = prep.preprocess_file(f)
# XXX: there seem to still be some '#' lines, which cause Cast to choke
source.gsub!(/(^\#.+)/, '')
begin
  ast = C.parse(source)
rescue C::ParseError => e
  p e
  # XXX: feature request #3
  line_num = e.message.match(/\d*/)[0].to_i
  puts source.lines.to_a[line_num-1]
end

The output of which is:

#<C::ParseError: 32:0: parse error on LPAREN (LPAREN)>
inline __attribute__ ((__always_inline__)) int __inline_isfinitel(long double);

So my guess is Cast doesn't support __attribute__, which I understand is not part of the C spec, but unfortunately is somewhat common in actual code. Description here: http://gcc.gnu.org/onlinedocs/gcc/Attribute-Syntax.html with all its infelicities.

[oggy]

Can you just add __attribute__ as a macro that expands to nothing?

I think adding explicit support for this will be something of a slippery slope. Each compiler seems to do its own weird thing.

If there was a good way to package up compiler-specific tweaks for stuff like this, I'd go for it, but I don't have the time to implement it myself. Happy to discuss if it's something you're keen to send a PR for. :)

[alexdowad]

I have an implementation of __attribute__ ready. Just waiting to see if my first PR will be accepted before opening that one.

In response to @oggy's concern, one option would be to add separate classes C::Parser::ANSI and C::Parser::GNU, one which just accepts "vanilla" C, and one which accepts all the GCC extensions.