Re: [Opencxx-users] Unable to compile metaclass on Cygwin 1.5.18

[Stefan S. <se...@sy...>]

Maciej Leks wrote:
> Hi All,
> 
> I’ve made the latest version of OpenC++ based on the snapshot given by  
> some of this list expert on Cygwin 1.5.18-1 (gcc 3.4.4.).
> 
> Then, I was trying to compile one of the example that is injected with 
> the  distribution, as follows:
> 
> $ occ2 BeforeClass.mc
> occ2: command failed: /usr/local/bin/occ --private--external-driver -E  
> <BeforeClass.ii --private--output BeforeClass.occ.tmp  
> 2>BeforeClass.feedback
> 
> ..and the content of the BeforeClass.feedback is:

Could you please post the actual code which occ complains about ? (Just
the surrounding lines will probably do.)

Chances are indeed that occ is getting to its limits with modern C++
code (such as the type traits).

The problem stems from occ being a 'context-free' parser,
when the actual C++ grammar is not context-free. Specifically, a conformant
parser has to consider a symbol's type when it attemps to decide on
a particular production. Depending on whether a given symbol corresponds
to a variable, type, or template, the token stream is interpreted differently
(expression or type-id ? relational-expression or template-id ? Etc.)

As occ builds its symbol table only after the parsing stage is over, it
has to rely on heuristics, which sometimes fail.

I have been able to work with a (slightly enhanced) form of the OpenC++
parser class for some time, but as I'm now trying to parse template-heavy
code, even my version fails.
In the context of the synopsis project (http://synopsis.fresco.org) I
have thus started to rewrite the Parser class from scratch.

Regards,
		Stefan