Two Lines of C in Ruby Source


#1

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


#2

Hi,

At Mon, 23 Jan 2006 16:20:59 +0900,
Brian T. 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.


#3

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/stdarg.html

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. :slight_smile:

Thank you,
Brian T.


#4

Brian T. removed_email_address@domain.invalid 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-talk/140058


#5

On Tuesday 24 January 2006 09:53, Brian T. wrote:

#ifdef HAVE_PROTOTYPES

define _(args) args

#else

define _(args) ()

#endif
Are there still compilers that don’t support function prototypes?


#6

Spoiler warning:

http://ruby-talk.org/cgi-bin/scat.rb/ruby/ruby-talk/140058

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 T.


#7

Brian T. removed_email_address@domain.invalid writes:

Spoiler warning:

http://ruby-talk.org/cgi-bin/scat.rb/ruby/ruby-talk/140058

Thank you for your help Christian.

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

http://rubystuff.org/nodewrap/


#8

Thank you Christian. This is really neat.