Index: src/Unwind/AddressSpace.hpp
===================================================================
--- src/Unwind/AddressSpace.hpp
+++ src/Unwind/AddressSpace.hpp
@@ -57,9 +57,18 @@
 #endif // !defined(_LIBUNWIND_IS_BAREMETAL)
 #endif  // LIBCXXABI_ARM_EHABI
 
-#if defined(__linux__)
+#if defined(__CloudABI__) || defined(__FreeBSD__) || defined(__linux__)
 #if _LIBUNWIND_SUPPORT_DWARF_UNWIND && _LIBUNWIND_SUPPORT_DWARF_INDEX
 #include <link.h>
+// Macro for machine-independent access to the ELF program headers. This
+// macro is not available on some systems (e.g., FreeBSD). On these
+// systems the data structures are called Elf{32,64}_XXX. Define ElfW()
+// locally.
+#ifndef ElfW
+#define ElfW(type) ElfW2(__INTPTR_WIDTH__, type)
+#define ElfW2(width, type) ElfW3(width, type)
+#define ElfW3(width, type) Elf##width##_##type
+#endif
 #include "EHHeaderParser.hpp"
 #endif
 #endif