Re: Problem with sys_select on Cygwin

[Ken Brown]

On 3/19/2016 10:44 PM, Paul Eggert wrote:
> Ken Brown wrote:
> > Cygwin is changing its headers as of the next release so that sys/types.h
> > includes sys/select.h....
> > Can sys_select be changed so that it doesn't try to include other
> > headers before
> > it has finished including sys/types.h?  Or is there some other way to
> > solve this
> > problem?
>
> Probably the latter. Why is Cygwin changing its headers? What is it
> changing? This may help us to provide a special case in Gnulib to solve
> the problem.  For example, we might be able to add Cygwin to the
> existing mess of code near the start of lib/sys_select.in.h that does
> something special for __osf__ and/or for __sun.

Eric can probably explain this better than I can, but I'll give it a 
try.  Newlib, which provides Cygwin's libc, has just had a complete 
overhaul of its feature test macros, with the goal of increasing 
compatibility with Glibc and/or BSD.  The relevant change to sys/types.h 
is simply

--- a/newlib/libc/include/sys/types.h
+++ b/newlib/libc/include/sys/types.h
@@ -87,5 +87,7 @@
 # if   __BSD_VISIBLE

+#include <sys/select.h>
+
 #  define      physadr         physadr_t
 #  define      quad            quad_t

I gather that __BSD_VISIBLE is similar to Glibc's __USE_MISC, which 
Glibc uses to guard the inclusion of sys/select.h.

Ken