Cygwin: don't export _feinitialise from newlib

Use the more official fesetenv(FE_DFL_ENV) from _dll_crt0, thus
allowing to drop the _feinitialise declaration from fenv.h.

Provide a no-op _feinitialise in Cygwin as exportable symbol for really
old applications when _feinitialise was called from mainCRTStartup in
crt0.o.

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

newlib/libc/machine/shared_x86/sys/fenv.h

@@ -170,11 +170,6 @@ int fegetprec (void);
 int fesetprec (int __prec);
 #endif
 
-#ifdef __INSIDE_CYGWIN__
-/* Cygwin-internal ONLY. */
-extern void _feinitialise ();
-#endif
-
 #endif /* __CYGWIN__ */
 
 #ifdef __cplusplus

newlib/libm/machine/shared_x86/fenv.c

@@ -63,10 +63,8 @@ static inline bool use_sse(void)
   return false;
 }
 
-#ifndef __CYGWIN__
 /* forward declaration */
 static void _feinitialise (void);
-#endif
 
 /*  This function enables traps for each of the exceptions as indicated
    by the parameter except. The individual exceptions are described in
@@ -451,10 +449,7 @@ fesetprec (int prec)
 #endif
 
 /*  Set up the FPU and SSE environment at the start of execution.  */
-#ifndef __CYGWIN__
+static void
-static
-#endif
-void
 _feinitialise (void)
 {
   extern fenv_t __fe_dfl_env;

winsup/cygwin/Makefile.in

@@ -288,6 +288,7 @@ DLL_OFILES:= \
 	exec.o \
 	external.o \
 	fcntl.o \
+	fenv.o \
 	fhandler.o \
 	fhandler_clipboard.o \
 	fhandler_console.o \

winsup/cygwin/dcrt0.cc

@@ -1085,7 +1085,7 @@ _dll_crt0 ()
     fork_info->alloc_stack ();
 #endif
 
-  _feinitialise ();
+  fesetenv (FE_DFL_ENV);
   _main_tls = &_my_tls;
   _main_tls->call ((DWORD (*) (void *, void *)) dll_crt0_1, NULL);
 }

winsup/cygwin/fenv.c

@@ -0,0 +1,5 @@
+/* no-op function as entry point for applications built between
+   2010-09-11 and 2011-03-16.  That's the timeframe of _feinitialise
+   being called from mainCRTStartup in crt0.o. */
+void _feinitialise (void)
+{}