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comp.lang.ruby

Two Lines of C in Ruby Source

Brian Takita

1/23/2006 7:21:00 AM

Hello,

Can somebody tell me what these lines of code mean?

extern int snprintf __((char *, size_t n, char const *, ...));
extern int vsnprintf _((char *, size_t n, char const *, va_list));

I am confused over what _, __, and ... mean.

They are in missing.h lines 134 - 135

--
Thank you,
Brian Takita
http://weblog.freeo...
7 Answers

Nobuyoshi Nakada

1/23/2006 7:31:00 AM

0

Hi,

At Mon, 23 Jan 2006 16:20:59 +0900,
Brian Takita wrote in [ruby-talk:176520]:
> I am confused over what _, __, and ... mean.

See defines.h for _ and __. Look for a tutorial of C for ...

Ruby source and extensions are not good as a tutorial.

--
Nobu Nakada

Brian Takita

1/24/2006 8:53:00 AM

0

> See defines.h for _ and __.
Thank you for the pointer. I found the defines.

#ifdef __cplusplus
# ifndef HAVE_PROTOTYPES
# define HAVE_PROTOTYPES 1
# endif
# ifndef HAVE_STDARG_PROTOTYPES
# define HAVE_STDARG_PROTOTYPES 1
# endif
#endif

#undef _
#ifdef HAVE_PROTOTYPES
# define _(args) args
#else
# define _(args) ()
#endif

#undef __
#ifdef HAVE_STDARG_PROTOTYPES
# define __(args) args
#else
# define __(args) ()
#endif

It looks like if __cplusplus is not defined, an empty argument field is
outputted. If __cplusplus is defined, the arguments are outputted by the
preprocessor.

... is a variable argument. stdarg.h is required for this.
More information can be found at
http://www.thinkage.ca/english/gcos/expl/c/incl/s...

> Ruby source and extensions are not good as a tutorial.
I'm trying to find out where the File name and line number of methods are
stored. So far my search has lead me to look in the backtrace function in
eval.c: line 6094.

If you have any pointers to lead me in the right direction, I would
appreciate it very much.

Of course, looking at the ruby c source requires me to learn some c. :)

Thank you,
Brian Takita

Gioele Barabucci

1/24/2006 12:38:00 PM

0

On Tuesday 24 January 2006 09:53, Brian Takita wrote:
> #ifdef HAVE_PROTOTYPES
> # define _(args) args
> #else
> # define _(args) ()
> #endif
Are there still compilers that don't support function prototypes?

--
Gioele <dev@gioelebarabucci.com>

Christian Neukirchen

1/24/2006 6:17:00 PM

0

Brian Takita <brian.takita@gmail.com> writes:

> I'm trying to find out where the File name and line number of methods are
> stored. So far my search has lead me to look in the backtrace function in
> eval.c: line 6094.

Spoiler warning:
http://ruby-talk.org/cgi-bin/scat.rb/ruby/ruby-t...

--
Christian Neukirchen <chneukirchen@gmail.com> http://chneuk...

Brian Takita

1/25/2006 4:42:00 AM

0

>
> Spoiler warning:
>
> http://ruby-talk.org/cgi-bin/scat.rb/ruby/ruby-t...
>

Thank you for your help Christian.

Would there be a way to access the Node struct from a Ruby object?

My objective is to find all of the file and line numbers of the class,
module, and method definitions.
To me, it looks like it would require significant rewriting of the Ruby core
to easily achieve this.

The reason is I'm looking at
#define NEW_METHOD(n,x) NEW_NODE(NODE_METHOD,x,n,0)
...
#define NEW_CLASS(n,b,s) NEW_NODE(NODE_CLASS
#define NEW_SCLASS(r,b)
NEW_NODE(NODE_SCLASS,r,NEW_SCOPE(b),0),n,NEW_SCOPE(b),(s))
#define NEW_MODULE(n,b) NEW_NODE(NODE_MODULE,n,NEW_SCOPE(b),0)

in node.h

They are all called in parse.y, parse.c, class.c, and eval.c
It looks like set_trace_func is the best way to achieve this goal.


Thank you,
Brian Takita

Christian Neukirchen

1/25/2006 3:59:00 PM

0

Brian Takita <brian.takita@gmail.com> writes:

>>
>> Spoiler warning:
>>
>> http://ruby-talk.org/cgi-bin/scat.rb/ruby/ruby-t...
>>
>
> Thank you for your help Christian.
>
> Would there be a way to access the Node struct from a Ruby object?

http://rubystuff.org...

> Thank you,
> Brian Takita
--
Christian Neukirchen <chneukirchen@gmail.com> http://chneuk...

Brian Takita

1/27/2006 5:27:00 PM

0

Thank you Christian. This is really neat.

On 1/25/06, Christian Neukirchen <chneukirchen@gmail.com> wrote:
>
> Brian Takita <brian.takita@gmail.com> writes:
>
> >>
> >> Spoiler warning:
> >>
> >> http://ruby-talk.org/cgi-bin/scat.rb/ruby/ruby-t...
> >>
> >
> > Thank you for your help Christian.
> >
> > Would there be a way to access the Node struct from a Ruby object?
>
> http://rubystuff.org...
>
> > Thank you,
> > Brian Takita
> --
> Christian Neukirchen <chneukirchen@gmail.com> http://chneuk...
>
>