From dd24ca1cb76de9973220fed356540f190a05ac83 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= <bjorn@erlang.org>
Date: Tue, 30 Aug 2011 17:01:14 +0200
Subject: Fix build problems on MacOS 10.7 (Lion)

On MacOS 10.7 (Lion) with Xcode 4.1 installed, the default
C compiler is llvm-gcc-4.2. That compiler compiles beam_emu.c
incorrectly, resulting in an emulator that will not start.

The problem can be worked around by turning off all optimizations,
but that will significantly degrade the performance of the run-time
system. The problem can also be worked around manually like this:

  CC=gcc-4.2 ./configure

To allow a working system to be built "out of the box", have
the configure script set up the emulator Makefile so that gcc-4.2
will be used to compile beam_emu.c if the default compiler is
llvm-based. All other C files will still be compiled with the
default compiler.
---
 erts/aclocal.m4           |  5 ++++-
 erts/emulator/Makefile.in | 10 +++++-----
 2 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/erts/aclocal.m4 b/erts/aclocal.m4
index b64380e817..9956835dc8 100644
--- a/erts/aclocal.m4
+++ b/erts/aclocal.m4
@@ -125,6 +125,9 @@ AC_DEFUN(LM_FIND_EMU_CC,
 			ac_cv_prog_emu_cc,
 			[
 AC_TRY_COMPILE([],[
+#ifdef __llvm__
+#error "llvm is currently unable to compile beam_emu.c"
+#endif
     __label__ lbl1;
     __label__ lbl2;
     int x = magic();
@@ -140,7 +143,7 @@ lbl2:
 ],ac_cv_prog_emu_cc=$CC,ac_cv_prog_emu_cc=no)
 
 if test $ac_cv_prog_emu_cc = no; then
-	for ac_progname in emu_cc.sh gcc; do
+	for ac_progname in emu_cc.sh gcc-4.2 gcc; do
   		IFS="${IFS= 	}"; ac_save_ifs="$IFS"; IFS=":"
   		ac_dummy="$PATH"
   		for ac_dir in $ac_dummy; do
diff --git a/erts/emulator/Makefile.in b/erts/emulator/Makefile.in
index b658e79378..620402fbfb 100644
--- a/erts/emulator/Makefile.in
+++ b/erts/emulator/Makefile.in
@@ -598,11 +598,6 @@ INCLUDES += -I$(ERL_TOP)/erts/etc/vxworks
 endif
 
 ifeq ($(TARGET),win32)
-# Usually the same as the default rule, but certain platforms (i.e. win32) mix
-# different compilers
-$(OBJDIR)/beam_emu.o: beam/beam_emu.c
-	$(EMU_CC) $(subst -O2, $(GEN_OPT_FLGS), $(CFLAGS)) $(INCLUDES) -c $< -o $@
-
 $(OBJDIR)/dll_sys.o: sys/$(ERLANG_OSTYPE)/sys.c
 	$(CC) $(CFLAGS) -DERL_RUN_SHARED_LIB=1 $(INCLUDES) -c $< -o $@
 
@@ -616,6 +611,11 @@ $(OBJDIR)/beam_emu.o: beam/beam_emu.c
 	$(CC) $(subst -O2, $(GEN_OPT_FLGS), $(CFLAGS)) \
          -OPT:Olimit=0 -WOPT:lpre=off:spre=off:epre=off \
          $(INCLUDES) -c $< -o $@
+else
+# Usually the same as the default rule, but certain platforms (e.g. win32) mix
+# different compilers
+$(OBJDIR)/beam_emu.o: beam/beam_emu.c
+	$(EMU_CC) $(subst -O2, $(GEN_OPT_FLGS), $(CFLAGS)) $(INCLUDES) -c $< -o $@
 endif
 
 
-- 
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