Index: compiler-rt/lib/tsan/rtl/tsan_interceptors_posix.cpp
===================================================================
--- compiler-rt/lib/tsan/rtl/tsan_interceptors_posix.cpp
+++ compiler-rt/lib/tsan/rtl/tsan_interceptors_posix.cpp
@@ -31,6 +31,8 @@
 #include "tsan_mman.h"
 #include "tsan_fd.h"
 
+#include <stdarg.h>
+
 using namespace __tsan;
 
 #if SANITIZER_FREEBSD || SANITIZER_MAC
@@ -135,6 +137,7 @@
 #endif
 const int MAP_FIXED = 0x10;
 typedef long long_t;
+typedef __sanitizer::u16 mode_t;
 
 // From /usr/include/unistd.h
 # define F_ULOCK 0      /* Unlock a previously locked region.  */
@@ -1508,20 +1511,28 @@
 #define TSAN_MAYBE_INTERCEPT_FSTAT64
 #endif
 
-TSAN_INTERCEPTOR(int, open, const char *name, int flags, int mode) {
-  SCOPED_TSAN_INTERCEPTOR(open, name, flags, mode);
+TSAN_INTERCEPTOR(int, open, const char *name, int oflag, ...) {
+  va_list ap;
+  va_start(ap, oflag);
+  mode_t mode = va_arg(ap, int);
+  va_end(ap);
+  SCOPED_TSAN_INTERCEPTOR(open, name, oflag, mode);
   READ_STRING(thr, pc, name, 0);
-  int fd = REAL(open)(name, flags, mode);
+  int fd = REAL(open)(name, oflag, mode);
   if (fd >= 0)
     FdFileCreate(thr, pc, fd);
   return fd;
 }
 
 #if SANITIZER_LINUX
-TSAN_INTERCEPTOR(int, open64, const char *name, int flags, int mode) {
-  SCOPED_TSAN_INTERCEPTOR(open64, name, flags, mode);
+TSAN_INTERCEPTOR(int, open64, const char *name, int oflag, ...) {
+  va_list ap;
+  va_start(ap, oflag);
+  mode_t mode = va_arg(ap, int);
+  va_end(ap);
+  SCOPED_TSAN_INTERCEPTOR(open64, name, oflag, mode);
   READ_STRING(thr, pc, name, 0);
-  int fd = REAL(open64)(name, flags, mode);
+  int fd = REAL(open64)(name, oflag, mode);
   if (fd >= 0)
     FdFileCreate(thr, pc, fd);
   return fd;
Index: compiler-rt/test/tsan/Darwin/variadic-open.cpp
===================================================================
--- /dev/null
+++ compiler-rt/test/tsan/Darwin/variadic-open.cpp
@@ -0,0 +1,24 @@
+// RUN: %clangxx_tsan -O1 %s -o %t && %run %t %t.tmp 2>&1 | FileCheck %s
+#include <stdio.h>
+#include <assert.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <sys/stat.h>
+
+int main(int argc, char *argv[]) {
+  fprintf(stderr, "Hello world.\n");
+  assert(argv[1]);
+  unlink(argv[1]);
+  int fd = open(argv[1], O_RDWR | O_CREAT, 0644);
+  assert(fd != -1);
+  struct stat info;
+  int result = fstat(fd, &info);
+  fprintf(stderr, "permissions = 0%o\n", info.st_mode & ~S_IFMT);
+  assert(result == 0);
+  close(fd);
+  fprintf(stderr, "Done.\n");
+}
+
+// CHECK: Hello world.
+// CHECK: permissions = 0644
+// CHECK: Done.