Merge branch 'rickard/configure-defaults/OTP-11723'

* rickard/configure-defaults/OTP-11723:
  Always default to disabled floating point exceptions on Linux

HOWTO/INSTALL.md

@@ -268,6 +268,11 @@ Some of the available `configure` options are:
     default if possible)
 *   `--{enable,disable}-hipe` - HiPE support (enabled by default on supported
     platforms)
+*   `--{enable,disable}-fp-exceptions` - Floating point exceptions (an
+    optimization for floating point operations). The default differs
+    depending on operating system and hardware platform. Note that by
+    enabling this you might get a seemingly working system that sometimes
+    fail on floating point operations.
 *   `--enable-darwin-universal` - Build universal binaries on darwin i386.
 *   `--enable-darwin-64bit` - Build 64-bit binaries on darwin
 *   `--enable-m64-build` - Build 64-bit binaries using the `-m64` flag to
@@ -293,7 +298,7 @@ Some of the available `configure` options are:
     memory accesses. If `configure` should inform you about no native atomic
     implementation available, you typically want to try using the
     `libatomic_ops` library. It can be downloaded from
-    <http://www.hpl.hp.com/research/linux/atomic_ops/>.
+    <https://github.com/ivmai/libatomic_ops/>.
 *   `--disable-smp-require-native-atomics` - By default `configure` will
     fail if an SMP runtime system is about to be built, and no implementation
     for native atomic memory accesses can be found. If this happens, you are

erts/configure.in

@@ -2798,6 +2798,11 @@ esac
 
 if test X${enable_fp_exceptions} = Xauto ; then
    case $host_os in
+   	*linux*)
+	      enable_fp_exceptions=no
+	      AC_MSG_NOTICE([Floating point exceptions disabled by default on Linux]) ;;
+	      *)
+	      ;;
 	darwin*)
 	      enable_fp_exceptions=no
 	      AC_MSG_NOTICE([Floating point exceptions disabled by default on MacOS X]) ;;

otp_build

@@ -173,6 +173,14 @@ determine_version_controller ()
 # Special static config flags for certain platforms are set here  
 set_config_flags ()
 {
+	#
+	# NOTE! Do not add special flags here without a *very good*
+	#       reason. We normally do not want "./otp_build configure"
+	#       and "./configure" to produce different results.
+	#       However, in the Windows case this does not matter, since
+	#       the only supported way to build on Windows is using
+	#       otp_build.
+	#
 	# * Extra flags to pass to configure are placed in `CONFIG_FLAGS'.
 	# * The command line is no longer added to `CONFIG_FLAGS' by
 	#   `set_config_flags'. It is instead passed directly to
@@ -183,16 +191,6 @@ set_config_flags ()
 	#   (in the cross compilation case the whole command line as well as
 	#   the cross configuration have been moved here). 
 
-	if target_contains linux; then 
-	        XX=`echo $* | grep -v able-fp-exceptions`
-		if [ "$*" = "$XX" ]; then 
-		    CONFIG_FLAGS="$CONFIG_FLAGS --disable-fp-exceptions"
-		fi
-	fi
-	if target_contains "univel-sysv4"; then
-		CONFIG_FLAGS="$CONFIG_FLAGS --x-libraries=/usr/lib/X11"
-	fi
-
 	if target_contains free_source; then
 		CONFIG_FLAGS="$CONFIG_FLAGS --host=$TARGET"
 	fi