Take out (parts of) broken fp exception support for MacOS X

Floating-point exception support on MacOS X has never been especially
reliable, and has therefore been disabled by default for a long time.

The fpe support is now broken.

Therefore, take out the unnecessary test for modern mcontext in
configure (whatever that means) and the associated code in sys_float.c.
Add #error directives to sys_float.c to make it clear that
fpe is not supported.

It seems to risky to mess with the mess of #ifdef's, so we will
not attempt to remove all fpe support code for MacOS X.

2 files changed, 3 insertions, 61 deletions

diff --git a/erts/configure.in b/erts/configure.in
index 854bdbdc15..cae3843465 100644
--- a/erts/configure.in
+++ b/erts/configure.in
@@ -2807,44 +2807,6 @@ if test "$cross_compiling" != "yes" && test X${enable_hipe} != Xno; then
   fi
 fi
 
-case $ARCH-$OPSYS in
-	amd64-darwin*|x86-darwin*)
-		AC_MSG_CHECKING([For modern (leopard) style mcontext_t])
-		AC_TRY_COMPILE([
-				#include <stdlib.h>
-				#include <sys/types.h>
-				#include <unistd.h>
-				#include <mach/mach.h>
-				#include <pthread.h>
-				#include <machine/signal.h>
-				#include <ucontext.h>
-				],[
-				#if defined(__APPLE__) && defined(__MACH__) && !defined(__DARWIN__)
-				#define __DARWIN__ 1
-				#endif
-
-				#ifndef __DARWIN__
-				#error inpossible
-				#else
-
-				mcontext_t mc = NULL;
-				int x = mc->__fs.__fpu_mxcsr;
-
-				#endif
-				],darwin_mcontext_leopard=yes,
-				darwin_mcontext_leopard=no)
-				if test X"$darwin_mcontext_leopard" = X"yes"; then
-				   AC_DEFINE(DARWIN_MODERN_MCONTEXT,[],[Modern style mcontext_t in MacOSX])
-				   AC_MSG_RESULT(yes)
-				else
-				   AC_MSG_RESULT(no)
-				fi
-		;;
-	*)
-		darwin_mcontext_leopard=no
-		;;
-esac
-
 if test X${enable_fp_exceptions} = Xauto ; then
    case $host_os in
    	*linux*)
diff --git a/erts/emulator/sys/unix/sys_float.c b/erts/emulator/sys/unix/sys_float.c
index 8fe7e599e5..89e2484b17 100644
--- a/erts/emulator/sys/unix/sys_float.c
+++ b/erts/emulator/sys/unix/sys_float.c
@@ -499,18 +499,8 @@ static int mask_fpe(void)
 #define mc_pc(mc)	((mc)->gregs[REG_RIP])
 #elif defined(__linux__) && defined(__i386__)
 #define mc_pc(mc)	((mc)->gregs[REG_EIP])
-#elif defined(__DARWIN__) && defined(__i386__)
-#ifdef DARWIN_MODERN_MCONTEXT
-#define mc_pc(mc)	((mc)->__ss.__eip)
-#else
-#define mc_pc(mc)	((mc)->ss.eip)
-#endif
-#elif defined(__DARWIN__) && defined(__x86_64__)
-#ifdef DARWIN_MODERN_MCONTEXT
-#define mc_pc(mc)	((mc)->__ss.__rip)
-#else
-#define mc_pc(mc)	((mc)->ss.rip)
-#endif
+#elif defined(__DARWIN__)
+# error "Floating-point exceptions not supported on MacOS X"
 #elif defined(__FreeBSD__) && defined(__x86_64__)
 #define mc_pc(mc)	((mc)->mc_rip)
 #elif defined(__FreeBSD__) && defined(__i386__)
@@ -575,17 +565,7 @@ static void fpe_sig_action(int sig, siginfo_t *si, void *puc)
     regs[PT_FPSCR] = 0x80|0x40|0x10;	/* VE, OE, ZE; not UE or XE */
 #endif
 #elif defined(__DARWIN__) && (defined(__i386__) || defined(__x86_64__))
-#ifdef DARWIN_MODERN_MCONTEXT
-    mcontext_t mc = uc->uc_mcontext;
-    pc = mc_pc(mc);
-    mc->__fs.__fpu_mxcsr = 0x1F80;
-    *(unsigned short *)&mc->__fs.__fpu_fsw &= ~0xFF;
-#else
-    mcontext_t mc = uc->uc_mcontext;
-    pc = mc_pc(mc);
-    mc->fs.fpu_mxcsr = 0x1F80;
-    *(unsigned short *)&mc->fs.fpu_fsw &= ~0xFF;
-#endif /* DARWIN_MODERN_MCONTEXT */
+# error "Floating-point exceptions not supported on MacOS X"
 #elif defined(__DARWIN__) && defined(__ppc__)
     mcontext_t mc = uc->uc_mcontext;
     pc = mc->ss.srr0;