add __dead__ annotation support

CMakeLists.txt

@@ -49,6 +49,7 @@ endif()
 
 if(CMAKE_SYSTEM_NAME MATCHES "OpenBSD")
 	add_definitions(-DHAVE_ATTRIBUTE__BOUNDED__)
+	add_definitions(-DHAVE_ATTRIBUTE__DEAD__)
 endif()
 
 if(CMAKE_SYSTEM_NAME MATCHES "Linux")

include/compat/sys/types.h

@@ -49,6 +49,14 @@ typedef SSIZE_T ssize_t;
 # define __bounded__(x, y, z)
 #endif
 
+#if !defined(HAVE_ATTRIBUTE__DEAD) && !defined(__dead)
+#ifdef _MSC_VER
+#define __dead      __declspec(noreturn)
+#else
+#define __dead      __attribute__((__noreturn__))
+#endif
+#endif
+
 #ifdef _WIN32
 #define __warn_references(sym,msg)
 #else

m4/check-os-options.m4

@@ -98,6 +98,7 @@ char buf[1]; getentropy(buf, 1);
 		HOST_OS=openbsd
 		HOST_ABI=elf
 		AC_DEFINE([HAVE_ATTRIBUTE__BOUNDED__], [1], [OpenBSD gcc has bounded])
+		AC_DEFINE([HAVE_ATTRIBUTE__DEAD], [1], [OpenBSD gcc has __dead])
 		;;
 	*mingw*)
 		HOST_OS=win