From cc19109af966331f76cc8b6fd7c92eec36dc2276 Mon Sep 17 00:00:00 2001
From: Corinna Vinschen <corinna@vinschen.de>
Date: Wed, 24 Mar 2021 11:06:58 +0100
Subject: [PATCH] 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 | 5 -----
 newlib/libm/machine/shared_x86/fenv.c     | 7 +------
 winsup/cygwin/Makefile.in                 | 1 +
 winsup/cygwin/dcrt0.cc                    | 2 +-
 winsup/cygwin/fenv.c                      | 5 +++++
 5 files changed, 8 insertions(+), 12 deletions(-)
 create mode 100644 winsup/cygwin/fenv.c

diff --git a/newlib/libc/machine/shared_x86/sys/fenv.h b/newlib/libc/machine/shared_x86/sys/fenv.h
index e0408fe5b..243cac27a 100644
--- a/newlib/libc/machine/shared_x86/sys/fenv.h
+++ b/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
diff --git a/newlib/libm/machine/shared_x86/fenv.c b/newlib/libm/machine/shared_x86/fenv.c
index 8d1f1ad7f..ccc08e2d8 100644
--- a/newlib/libm/machine/shared_x86/fenv.c
+++ b/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
-#endif
-void
+static void
 _feinitialise (void)
 {
   extern fenv_t __fe_dfl_env;
diff --git a/winsup/cygwin/Makefile.in b/winsup/cygwin/Makefile.in
index ff6798867..73d9b37fd 100644
--- a/winsup/cygwin/Makefile.in
+++ b/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 \
diff --git a/winsup/cygwin/dcrt0.cc b/winsup/cygwin/dcrt0.cc
index 810017956..d4a08d18b 100644
--- a/winsup/cygwin/dcrt0.cc
+++ b/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);
 }
diff --git a/winsup/cygwin/fenv.c b/winsup/cygwin/fenv.c
new file mode 100644
index 000000000..80f7cc52c
--- /dev/null
+++ b/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)
+{}
-- 
2.43.5