[Problem] mempcpy is missing? (FAQ alert)

[Charles Wilson]

Christopher Faylor wrote:

> So, the cygwin bug report is noted and appreciated.  We'll fix this
> eventually.  However, the "correct" fix is to modify the configury
> mechanism which trips up on this in libintl.
> 
> I guess I can't get by without giving the long answers to reports
> like this...  We should add this to the FAQ.

That is, you should check both for the appropriate header, and for the 
function.  Some (bad) configure.in's check only for "memcpy.h" (or 
whatever), but don't check that the function memcpy() can actually be 
linked.  The right incantation is

in configure.in:

AC_CHECK_HEADERS([memcpy.h ...])
AC_CHECK_FUNCS([memcpy ...])

And in your C code, guard with

#if defined(HAVE_MEMCPY_H) && defined(HAVE_MEMCPY)
memcpy code here...
#endif

Technically, this is an autoconf question -- but it crops up on cygwin 
often.  Mainly, because there are so many "regular C library functions" 
that are missing from newlib, but slowly get added to it (and hence, 
added to cygwin) such that the cygwin exports are often behind -- and we 
have the header <direct from newlib> but don't make the function 
visible.  Thus, we're a good testbed for revealing these third-party 
packages which make too many assumptions in their configury.

Chris is right -- this is really a problem with the third party package. 
  But we probably need a blurb in the FAQ about it anyway.

--Chuck


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