Index: compiler-rt/lib/sanitizer_common/sanitizer_platform.h
--- compiler-rt/lib/sanitizer_common/sanitizer_platform.h.orig
+++ compiler-rt/lib/sanitizer_common/sanitizer_platform.h
@@ -13,6 +13,7 @@
 #define SANITIZER_PLATFORM_H
 
 #if !defined(__linux__) && !defined(__FreeBSD__) && !defined(__NetBSD__) && \
+    !defined(__OpenBSD__) && \
     !defined(__APPLE__) && !defined(_WIN32) && !defined(__Fuchsia__) &&     \
     !(defined(__sun__) && defined(__svr4__))
 #  error "This operating system is not supported"
@@ -49,6 +50,12 @@
 #  define SANITIZER_NETBSD 0
 #endif
 
+#if defined(__OpenBSD__)
+# define SANITIZER_OPENBSD 1
+#else
+# define SANITIZER_OPENBSD 0
+#endif
+
 #if defined(__sun__) && defined(__svr4__)
 #  define SANITIZER_SOLARIS 1
 #else
@@ -138,7 +145,7 @@
 
 #define SANITIZER_POSIX                                     \
   (SANITIZER_FREEBSD || SANITIZER_LINUX || SANITIZER_APPLE || \
-   SANITIZER_NETBSD || SANITIZER_SOLARIS)
+    SANITIZER_NETBSD || SANITIZER_OPENBSD || SANITIZER_SOLARIS)
 
 #if __LP64__ || defined(_WIN64)
 #  define SANITIZER_WORDSIZE 64
