diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_common_interceptors.inc b/compiler-rt/lib/sanitizer_common/sanitizer_common_interceptors.inc
--- a/compiler-rt/lib/sanitizer_common/sanitizer_common_interceptors.inc
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_common_interceptors.inc
@@ -957,6 +957,7 @@
   // Assuming frexp() always writes to |exp|.
   COMMON_INTERCEPTOR_WRITE_RANGE(ctx, exp, sizeof(*exp));
   double res = REAL(frexp)(x, exp);
+  COMMON_INTERCEPTOR_INITIALIZE_RANGE(exp, sizeof(*exp));
   return res;
 }
 
@@ -969,22 +970,18 @@
 INTERCEPTOR(float, frexpf, float x, int *exp) {
   void *ctx;
   COMMON_INTERCEPTOR_ENTER(ctx, frexpf, x, exp);
-  // FIXME: under ASan the call below may write to freed memory and corrupt
-  // its metadata. See
-  // https://github.com/google/sanitizers/issues/321.
-  float res = REAL(frexpf)(x, exp);
   COMMON_INTERCEPTOR_WRITE_RANGE(ctx, exp, sizeof(*exp));
+  COMMON_INTERCEPTOR_INITIALIZE_RANGE(exp, sizeof(*exp));
+  float res = REAL(frexpf)(x, exp);
   return res;
 }
 
 INTERCEPTOR(long double, frexpl, long double x, int *exp) {
   void *ctx;
   COMMON_INTERCEPTOR_ENTER(ctx, frexpl, x, exp);
-  // FIXME: under ASan the call below may write to freed memory and corrupt
-  // its metadata. See
-  // https://github.com/google/sanitizers/issues/321.
-  long double res = REAL(frexpl)(x, exp);
   COMMON_INTERCEPTOR_WRITE_RANGE(ctx, exp, sizeof(*exp));
+  long double res = REAL(frexpl)(x, exp);
+  COMMON_INTERCEPTOR_INITIALIZE_RANGE(exp, sizeof(*exp));
   return res;
 }
 
diff --git a/compiler-rt/test/asan/TestCases/frexpf_interceptor.cpp b/compiler-rt/test/asan/TestCases/frexpf_interceptor.cpp
new file mode 100644
--- /dev/null
+++ b/compiler-rt/test/asan/TestCases/frexpf_interceptor.cpp
@@ -0,0 +1,16 @@
+// RUN: %clangxx_asan -O0 %s -o %t && not %run %t 2>&1 | FileCheck %s
+
+// Test the frexpf() interceptor.
+
+#include <math.h>
+#include <stdio.h>
+#include <stdlib.h>
+int main() {
+  float x = 3.14;
+  int *exp = (int *)malloc(sizeof(int));
+  free(exp);
+  double y = frexpf(x, exp);
+  // CHECK: use-after-free
+  // CHECK: SUMMARY
+  return 0;
+}
diff --git a/compiler-rt/test/asan/TestCases/frexpl_interceptor.cpp b/compiler-rt/test/asan/TestCases/frexpl_interceptor.cpp
new file mode 100644
--- /dev/null
+++ b/compiler-rt/test/asan/TestCases/frexpl_interceptor.cpp
@@ -0,0 +1,16 @@
+// RUN: %clangxx_asan -O0 %s -o %t && not %run %t 2>&1 | FileCheck %s
+
+// Test the frexpl() interceptor.
+
+#include <math.h>
+#include <stdio.h>
+#include <stdlib.h>
+int main() {
+  long double x = 3.14;
+  int *exp = (int *)malloc(sizeof(int));
+  free(exp);
+  double y = frexpl(x, exp);
+  // CHECK: use-after-free
+  // CHECK: SUMMARY
+  return 0;
+}