From 10b064ffe902d5af31bb49bd8e4f03c545f8d462 Mon Sep 17 00:00:00 2001
From: Ladislav Michl <ladis@linux-mips.org>
Date: Tue, 13 Nov 2012 11:19:47 +0100
Subject: [PATCH] Support building with older compilers.

Add a check for __builtin_unreachable.

Upstream-Status: Pending
---
 configure.ac          |   11 +++++++++++
 include/libunwind_i.h |    6 ++++++
 src/arm/Gresume.c     |    2 +-
 src/sh/Gresume.c      |    2 +-
 4 files changed, 19 insertions(+), 2 deletions(-)

--- a/configure.ac
+++ b/configure.ac
@@ -285,6 +285,17 @@ if test x$have__builtin___clear_cache =
 fi
 AC_MSG_RESULT([$have__builtin___clear_cache])
 
+AC_MSG_CHECKING([for __builtin_unreachable])
+AC_LINK_IFELSE(
+  [AC_LANG_PROGRAM([[]], [[__builtin_unreachable()]])],
+  [have__builtin_unreachable=yes],
+  [have__builtin_unreachable=no])
+if test x$have__builtin_unreachable = xyes; then
+  AC_DEFINE([HAVE__BUILTIN_UNREACHABLE], [1],
+            [Defined if __builtin_unreachable() is available])
+fi
+AC_MSG_RESULT([$have__builtin_unreachable])
+
 AC_MSG_CHECKING([for __sync atomics])
 AC_LINK_IFELSE(
   [AC_LANG_PROGRAM([[]], [[
--- a/include/libunwind_i.h
+++ b/include/libunwind_i.h
@@ -72,6 +72,12 @@ WITH THE SOFTWARE OR THE USE OR OTHER DE
 # endif
 #endif
 
+#if defined(HAVE__BUILTIN_UNREACHABLE)
+# define unreachable() __builtin_unreachable()
+#else
+# define unreachable() do { } while (1)
+#endif
+
 #ifdef DEBUG
 # define UNW_DEBUG	1
 #else
--- a/src/arm/Gresume.c
+++ b/src/arm/Gresume.c
@@ -96,7 +96,7 @@ arm_local_resume (unw_addr_space_t as, u
 	: : "r" (c->sigcontext_sp), "r" (c->sigcontext_pc)
       );
    }
-  __builtin_unreachable();
+  unreachable();
 #else
   printf ("%s: implement me\n", __FUNCTION__);
 #endif
--- a/src/sh/Gresume.c
+++ b/src/sh/Gresume.c
@@ -109,7 +109,7 @@ sh_local_resume (unw_addr_space_t as, un
 	  "r" (c->sigcontext_pc)
       );
    }
-  __builtin_unreachable();
+  unreachable();
 #endif
   return -UNW_EINVAL;
 }