glibc devel info pages

[Brian May <bam@debian.org>]

Hello,

What is the quickest way to look up a include file required
for a given function in glibc?

Before, with the man page system, I would be able to type in "man
vasprintf" and all the information I ever required would be presented
on the screen right in front of me.

Now, it seems that I have to type:

info libc<enter>
ivasprintf<enter>

and I find a limited 2 line description which still does not answer my
initial question.

This is my one and only dislike of info pages - that it seems so
difficult to find anything. Not only is it difficult to get to the
correct info page, but once you get there the information is
unstructured and incomplete.

If I look at the stdio.h, I see:

#ifdef __USE_GNU
/* Write formatted output to a string dynamically allocated with `malloc'.
   Store the address of the string in *PTR.  */
extern int vasprintf __P ((char **__restrict __ptr,
                           __const char *__restrict __f, _G_va_list __arg))
     __attribute__ ((__format__ (__printf__, 2, 0)));
[...]
#endif

so the challenge seems to be what is the correct way to define
__USE_GNU (just #define __USE_GNU messes up other #include stuff).

Again, I would expect to see this somewhere under one of the info
pages, but which one?
-- 
Brian May <bam@debian.org>