2 files changed, 66 insertions, 0 deletions
diff --git a/lib/libcompiler_rt/gcc_personality_v0.c b/lib/libcompiler_rt/gcc_personality_v0.c
index 29e5be30712..0bc76562456 100644
--- a/lib/libcompiler_rt/gcc_personality_v0.c
+++ b/lib/libcompiler_rt/gcc_personality_v0.c
@@ -12,6 +12,17 @@
 #include "int_lib.h"
 
 #include <unwind.h>
+#if defined(__arm__) && !defined(__ARM_DWARF_EH__) && !defined(__USING_SJLJ_EXCEPTIONS__)
+/*
+ * When building with older compilers (e.g. clang <3.9), it is possible that we
+ * have a version of unwind.h which does not provide the EHABI declarations
+ * which are quired for the C personality to conform to the specification.  In
+ * order to provide forward compatibility for such compilers, we re-declare the
+ * necessary interfaces in the helper to permit a standalone compilation of the
+ * builtins (which contains the C unwinding personality for historical reasons).
+ */
+#include "unwind-ehabi-helpers.h"
+#endif
 
 /*
  * Pointer encodings documented at:
diff --git a/lib/libcompiler_rt/unwind-ehabi-helpers.h b/lib/libcompiler_rt/unwind-ehabi-helpers.h
new file mode 100644
index 00000000000..ccb0765975a
--- /dev/null
+++ b/lib/libcompiler_rt/unwind-ehabi-helpers.h
@@ -0,0 +1,55 @@
+/* ===-- arm-ehabi-helpers.h - Supplementary ARM EHABI declarations --------===
+ *
+ *                     The LLVM Compiler Infrastructure
+ *
+ * This file is dual licensed under the MIT and the University of Illinois Open
+ * Source Licenses. See LICENSE.TXT for details.
+ *
+ * ===--------------------------------------------------------------------=== */
+
+#ifndef UNWIND_EHABI_HELPERS_H
+#define UNWIND_EHABI_HELPERS_H
+
+#include <stdint.h>
+/* NOTE: see reasoning for this inclusion below */
+#include <unwind.h>
+
+#if !defined(__ARM_EABI_UNWINDER__)
+
+/*
+ * NOTE: _URC_OK, _URC_FAILURE must be present as preprocessor tokens.  This
+ * allows for a substitution of a constant which can be cast into the
+ * appropriate enumerated type.  This header is expected to always be included
+ * AFTER unwind.h (which is why it is forcefully included above).  This ensures
+ * that we do not overwrite the token for the enumeration.  Subsequent uses of
+ * the token would be clean to rewrite with constant values.
+ *
+ * The typedef redeclaration should be safe.  Due to the protection granted to
+ * us by the `__ARM_EABI_UNWINDER__` above, we are guaranteed that we are in a
+ * header not vended by gcc.  The HP unwinder (being an itanium unwinder) does
+ * not support EHABI, and the GNU unwinder, derived from the HP unwinder, also
+ * does not support EHABI as of the introduction of this header.  As such, we
+ * are fairly certain that we are in the LLVM case.  Here, _Unwind_State is a
+ * typedef, and so we can get away with a redeclaration.
+ *
+ * Guarded redefinitions of the needed unwind state prevent the redefinition of
+ * those states.
+ */
+
+#define _URC_OK       0
+#define _URC_FAILURE  9
+
+typedef uint32_t _Unwind_State;
+
+#if !defined(_US_UNWIND_FRAME_STARTING)
+#define _US_UNWIND_FRAME_STARTING ((_Unwind_State)1)
+#endif
+
+#if !defined(_US_ACTION_MASK)
+#define _US_ACTION_MASK ((_Unwind_State)3)
+#endif
+
+#endif
+
+#endif
+