From ecd4eceae98cfb1c83133bdeaa9095546ca8b7c6 Mon Sep 17 00:00:00 2001
From: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Date: Thu, 26 May 2016 15:05:48 +0200
Subject: [PATCH] Use <fenv.h> when available instead of <fpu_control.h>

musl libc (http://musl-libc.org lack the non-standard <fpu_control.h>
header, which is used in src/os/linux/{i386,x86_64}/init.c files to
setup the floating point precision. This patch makes it use the
standard C <fenv.h> header instead when available.

Original patch at Felix Janda at
https://sourceforge.net/p/jamvm/patches/6/, adapted to still use
<fpu_control.h> if <fenv.h> is not provided.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
---
 configure.ac               |  2 +-
 src/os/linux/i386/init.c   | 15 +++++++++++++++
 src/os/linux/x86_64/init.c | 15 +++++++++++++--
 3 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/configure.ac b/configure.ac
index 19f77e6..ce59a3e 100644
--- a/configure.ac
+++ b/configure.ac
@@ -279,7 +279,7 @@ fi
 
 dnl Checks for header files.
 AC_HEADER_STDC
-AC_CHECK_HEADERS(sys/time.h unistd.h endian.h sys/param.h locale.h alloca.h)
+AC_CHECK_HEADERS(sys/time.h unistd.h endian.h sys/param.h locale.h alloca.h fenv.h)
 
 if test "$enable_zip" != no; then
     AC_CHECK_HEADER(zlib.h,,AC_MSG_ERROR(zlib.h is missing))
diff --git a/src/os/linux/i386/init.c b/src/os/linux/i386/init.c
index d9c6648..8fefe7d 100644
--- a/src/os/linux/i386/init.c
+++ b/src/os/linux/i386/init.c
@@ -19,18 +19,33 @@
  * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  */
 
+#include "config.h"
+
+#if defined(HAVE_FENV_H)
+#include <fenv.h>
+#else
 #include <fpu_control.h>
+#endif
 
 /* Change floating point precision to double (64-bit) from
  * the extended (80-bit) Linux default. */
 
 void setDoublePrecision() {
+#if defined(HAVE_FENV_H)
+    fenv_t fenv;
+
+    fegetenv(&fenv);
+    fenv.__control_word &= ~0x300; /* _FPU_EXTENDED */
+    fenv.__control_word |= 0x200; /* _FPU_DOUBLE */
+    fesetenv(&fenv);
+#else
     fpu_control_t cw;
 
     _FPU_GETCW(cw);
     cw &= ~_FPU_EXTENDED;
     cw |= _FPU_DOUBLE;
     _FPU_SETCW(cw);
+#endif
 }
 
 void initialisePlatform() {
diff --git a/src/os/linux/x86_64/init.c b/src/os/linux/x86_64/init.c
index 9d55229..b42b14e 100644
--- a/src/os/linux/x86_64/init.c
+++ b/src/os/linux/x86_64/init.c
@@ -19,7 +19,11 @@
  * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  */
 
-#ifdef __linux__
+#include "config.h"
+
+#if defined(HAVE_FENV_H)
+#include <fenv.h>
+#else
 #include <fpu_control.h>
 #endif
 
@@ -30,7 +34,14 @@
 */
 
 void setDoublePrecision() {
-#ifdef __linux__
+#if defined(HAVE_FENV_H)
+    fenv_t fenv;
+
+    fegetenv(&fenv);
+    fenv.__control_word &= ~0x300; /*_FPU_EXTENDED */
+    fenv.__control_word |= 0x200; /*_FPU_DOUBLE */
+    fesetenv(&fenv);
+#else
     fpu_control_t cw;
 
     _FPU_GETCW(cw);
-- 
2.7.4