Fix bug #12805 with compilation error in the cygw32 build.

 src/makefile.w32-in ($(BLD)/w32fns.$(O)): Depend on $(NT_INC)/unistd.h.
 src/w32fns.c Include unistd.h, to avoid compiler warnings on Cygwin.
 (emacs_abort) [CYGWIN]: Don't call _open_osfhandle; instead, use
 file descriptor 2 for standard error.

1 files changed, 9 insertions, 1 deletions

diff --git a/src/w32fns.c b/src/w32fns.c
index 74bb2375ea5..18e29ecaaf5 100644
--- a/src/w32fns.c
+++ b/src/w32fns.c
@@ -27,6 +27,7 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 #include <errno.h>
 #include <math.h>
 #include <fcntl.h>
+#include <unistd.h>
 
 #include "lisp.h"
 #include "w32term.h"
@@ -7749,12 +7750,19 @@ emacs_abort (void)
 
         if (i)
           {
+#ifdef CYGWIN
+            int stderr_fd = 2;
+#else
             HANDLE errout = GetStdHandle (STD_ERROR_HANDLE);
-            int stderr_fd = -1, errfile_fd = -1;
+            int stderr_fd = -1;
+#endif
+            int errfile_fd = -1;
             int j;
 
+#ifndef CYGWIN
             if (errout && errout != INVALID_HANDLE_VALUE)
               stderr_fd = _open_osfhandle ((intptr_t)errout, O_APPEND | O_BINARY);
+#endif
             if (stderr_fd >= 0)
               write (stderr_fd, "\r\nBacktrace:\r\n", 14);
             errfile_fd = _open ("emacs_backtrace.txt", O_RDWR | O_CREAT | O_BINARY, S_IREAD | S_IWRITE);