Index: lib/sanitizer_common/sanitizer_platform_interceptors.h
===================================================================
--- lib/sanitizer_common/sanitizer_platform_interceptors.h
+++ lib/sanitizer_common/sanitizer_platform_interceptors.h
@@ -161,7 +161,7 @@
   SI_FREEBSD || SI_MAC || SI_LINUX_NOT_ANDROID
 #define SANITIZER_INTERCEPT_SIGPENDING SI_NOT_WINDOWS
 #define SANITIZER_INTERCEPT_SIGPROCMASK SI_NOT_WINDOWS
-#define SANITIZER_INTERCEPT_BACKTRACE SI_LINUX_NOT_ANDROID
+#define SANITIZER_INTERCEPT_BACKTRACE SI_FREEBSD || SI_LINUX_NOT_ANDROID
 #define SANITIZER_INTERCEPT_GETMNTENT SI_LINUX
 #define SANITIZER_INTERCEPT_GETMNTENT_R SI_LINUX_NOT_ANDROID
 #define SANITIZER_INTERCEPT_STATFS SI_FREEBSD || SI_MAC || SI_LINUX_NOT_ANDROID
Index: test/msan/backtrace.cc
===================================================================
--- test/msan/backtrace.cc
+++ test/msan/backtrace.cc
@@ -17,7 +17,7 @@
   char **s = backtrace_symbols(buf, sz);
   assert(s > 0);
   for (int i = 0; i < sz; ++i)
-    printf("%d\n", strlen(s[i]));
+    printf("%d\n", (int)strlen(s[i]));
 }
 
 int main(void) {
Index: test/msan/lit.cfg
===================================================================
--- test/msan/lit.cfg
+++ test/msan/lit.cfg
@@ -14,6 +14,9 @@
                      "-fno-omit-frame-pointer",
                      "-fno-optimize-sibling-calls",
                      "-m64"] + config.debug_info_flags
+# Some Msan tests leverage backtrace() which requires libexecinfo on FreeBSD.
+if config.host_os == 'FreeBSD':
+  clang_msan_cflags += ["-lexecinfo"]
 clang_msan_cxxflags = config.cxx_mode_flags + clang_msan_cflags
 
 def build_invocation(compile_flags):