diff --git a/Include/Python.h b/Include/Python.h
index cf87a5c..bece208 100644
--- a/Include/Python.h
+++ b/Include/Python.h
@@ -53,6 +53,15 @@
 #include "pyport.h"
 #include "pymacro.h"
 
+/* A convenient way for code to know if clang's memory sanitizer is enabled. */
+#if defined(__has_feature)
+#  if __has_feature(memory_sanitizer)
+#    if !defined(MEMORY_SANITIZER)
+#      define MEMORY_SANITIZER
+#    endif
+#  endif
+#endif
+
 /* Debug-mode build with pymalloc implies PYMALLOC_DEBUG.
  *  PYMALLOC_DEBUG is in error if pymalloc is not in use.
  */
diff --git a/Misc/NEWS.d/next/Core and Builtins/2018-11-12-11-38-06.bpo-35214.PCHKbX.rst b/Misc/NEWS.d/next/Core and Builtins/2018-11-12-11-38-06.bpo-35214.PCHKbX.rst
new file mode 100644
index 0000000..c7842f3
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2018-11-12-11-38-06.bpo-35214.PCHKbX.rst
@@ -0,0 +1,4 @@
+The interpreter and extension modules have had annotations added so that
+they work properly under clang's Memory Sanitizer.  A new configure flag
+--with-memory-sanitizer has been added to make test builds of this nature
+easier to perform.
diff --git a/Modules/_ctypes/callproc.c b/Modules/_ctypes/callproc.c
index ba154fe..33b7055 100644
--- a/Modules/_ctypes/callproc.c
+++ b/Modules/_ctypes/callproc.c
@@ -75,6 +75,10 @@
 #include <alloca.h>
 #endif
 
+#ifdef MEMORY_SANITIZER
+#include <sanitizer/msan_interface.h>
+#endif
+
 #if defined(_DEBUG) || defined(__MINGW32__)
 /* Don't use structured exception handling on Windows if this is defined.
    MingW, AFAIK, doesn't support it.
@@ -1125,6 +1129,13 @@
     rtype = _ctypes_get_ffi_type(restype);
     resbuf = alloca(max(rtype->size, sizeof(ffi_arg)));
 
+#ifdef MEMORY_SANITIZER
+    /* ffi_call actually initializes resbuf, but from asm, which
+     * MemorySanitizer can't detect. Avoid false positives from MSan. */
+    if (resbuf != NULL) {
+        __msan_unpoison(resbuf, max(rtype->size, sizeof(ffi_arg)));
+    }
+#endif
     avalues = (void **)alloca(sizeof(void *) * argcount);
     atypes = (ffi_type **)alloca(sizeof(ffi_type *) * argcount);
     if (!resbuf || !avalues || !atypes) {
diff --git a/Modules/_posixsubprocess.c b/Modules/_posixsubprocess.c
index 9661e38..7ee3f71 100644
--- a/Modules/_posixsubprocess.c
+++ b/Modules/_posixsubprocess.c
@@ -21,6 +21,10 @@
 #include <dirent.h>
 #endif
 
+#ifdef MEMORY_SANITIZER
+# include <sanitizer/msan_interface.h>
+#endif
+
 #if defined(__ANDROID__) && __ANDROID_API__ < 21 && !defined(SYS_getdents64)
 # include <sys/linux-syscalls.h>
 # define SYS_getdents64  __NR_getdents64
@@ -287,6 +291,9 @@
                                 sizeof(buffer))) > 0) {
             struct linux_dirent64 *entry;
             int offset;
+#ifdef MEMORY_SANITIZER
+            __msan_unpoison(buffer, bytes);
+#endif
             for (offset = 0; offset < bytes; offset += entry->d_reclen) {
                 int fd;
                 entry = (struct linux_dirent64 *)(buffer + offset);
diff --git a/Modules/faulthandler.c b/Modules/faulthandler.c
index 2f9c2f6..17bf3fa 100644
--- a/Modules/faulthandler.c
+++ b/Modules/faulthandler.c
@@ -1370,7 +1370,7 @@
 #ifdef HAVE_SIGALTSTACK
     if (stack.ss_sp != NULL) {
         /* Fetch the current alt stack */
-        stack_t current_stack;
+        stack_t current_stack = {};
         if (sigaltstack(NULL, &current_stack) == 0) {
             if (current_stack.ss_sp == stack.ss_sp) {
                 /* The current alt stack is the one that we installed.
diff --git a/Python/bootstrap_hash.c b/Python/bootstrap_hash.c
index 7b187f1..1b8f9d9 100644
--- a/Python/bootstrap_hash.c
+++ b/Python/bootstrap_hash.c
@@ -20,6 +20,10 @@
 #  endif
 #endif
 
+#ifdef MEMORY_SANITIZER
+#  include <sanitizer/msan_interface.h>
+#endif
+
 #ifdef Py_DEBUG
 int _Py_HashSecret_Initialized = 0;
 #else
@@ -143,6 +147,11 @@
         else {
             n = syscall(SYS_getrandom, dest, n, flags);
         }
+#  ifdef MEMORY_SANITIZER
+        if (n > 0) {
+             __msan_unpoison(dest, n);
+        }
+#  endif
 #endif
 
         if (n < 0) {
diff --git a/Python/pymath.c b/Python/pymath.c
index 6799d20..c1606bd 100644
--- a/Python/pymath.c
+++ b/Python/pymath.c
@@ -17,7 +17,9 @@
 
 /* inline assembly for getting and setting the 387 FPU control word on
    gcc/x86 */
-
+#ifdef MEMORY_SANITIZER
+__attribute__((no_sanitize_memory))
+#endif
 unsigned short _Py_get_387controlword(void) {
     unsigned short cw;
     __asm__ __volatile__ ("fnstcw %0" : "=m" (cw));
diff --git a/configure b/configure
index 3d66c1c..e9e33b3 100755
--- a/configure
+++ b/configure
@@ -819,6 +819,8 @@
 with_lto
 with_hash_algorithm
 with_address_sanitizer
+with_memory_sanitizer
+with_undefined_behavior_sanitizer
 with_libs
 with_system_expat
 with_system_ffi
@@ -1515,7 +1517,10 @@
   --with-hash-algorithm=[fnv|siphash24]
                           select hash algorithm
   --with-address-sanitizer
-                          enable AddressSanitizer
+                          enable AddressSanitizer (asan)
+  --with-memory-sanitizer enable MemorySanitizer (msan)
+  --with-undefined-behavior-sanitizer
+                          enable UndefinedBehaviorSanitizer (ubsan)
   --with-libs='lib1 ...'  link against additional libs
   --with-system-expat     build pyexpat module using an installed expat
                           library
@@ -10038,6 +10043,44 @@
 $as_echo "$withval" >&6; }
 BASECFLAGS="-fsanitize=address -fno-omit-frame-pointer $BASECFLAGS"
 LDFLAGS="-fsanitize=address $LDFLAGS"
+# ASan works by controlling memory allocation, our own malloc interferes.
+with_pymalloc="no"
+
+else
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+fi
+
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for --with-memory-sanitizer" >&5
+$as_echo_n "checking for --with-memory-sanitizer... " >&6; }
+
+# Check whether --with-memory_sanitizer was given.
+if test "${with_memory_sanitizer+set}" = set; then :
+  withval=$with_memory_sanitizer;
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $withval" >&5
+$as_echo "$withval" >&6; }
+BASECFLAGS="-fsanitize=memory -fsanitize-memory-track-origins=2 -fno-omit-frame-pointer $BASECFLAGS"
+LDFLAGS="-fsanitize=memory -fsanitize-memory-track-origins=2 $LDFLAGS"
+# MSan works by controlling memory allocation, our own malloc interferes.
+with_pymalloc="no"
+
+else
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+fi
+
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for --with-undefined-behavior-sanitizer" >&5
+$as_echo_n "checking for --with-undefined-behavior-sanitizer... " >&6; }
+
+# Check whether --with-undefined_behavior_sanitizer was given.
+if test "${with_undefined_behavior_sanitizer+set}" = set; then :
+  withval=$with_undefined_behavior_sanitizer;
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $withval" >&5
+$as_echo "$withval" >&6; }
+BASECFLAGS="-fsanitize=undefined $BASECFLAGS"
+LDFLAGS="-fsanitize=undefined $LDFLAGS"
 
 else
   { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
diff --git a/configure.ac b/configure.ac
index d1502df..15d03ba 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2854,11 +2854,37 @@
 AC_MSG_CHECKING(for --with-address-sanitizer)
 AC_ARG_WITH(address_sanitizer,
             AS_HELP_STRING([--with-address-sanitizer],
-                           [enable AddressSanitizer]),
+                           [enable AddressSanitizer (asan)]),
 [
 AC_MSG_RESULT($withval)
 BASECFLAGS="-fsanitize=address -fno-omit-frame-pointer $BASECFLAGS"
 LDFLAGS="-fsanitize=address $LDFLAGS"
+# ASan works by controlling memory allocation, our own malloc interferes.
+with_pymalloc="no"
+],
+[AC_MSG_RESULT(no)])
+
+AC_MSG_CHECKING(for --with-memory-sanitizer)
+AC_ARG_WITH(memory_sanitizer,
+            AS_HELP_STRING([--with-memory-sanitizer],
+                           [enable MemorySanitizer (msan)]),
+[
+AC_MSG_RESULT($withval)
+BASECFLAGS="-fsanitize=memory -fsanitize-memory-track-origins=2 -fno-omit-frame-pointer $BASECFLAGS"
+LDFLAGS="-fsanitize=memory -fsanitize-memory-track-origins=2 $LDFLAGS"
+# MSan works by controlling memory allocation, our own malloc interferes.
+with_pymalloc="no"
+],
+[AC_MSG_RESULT(no)])
+
+AC_MSG_CHECKING(for --with-undefined-behavior-sanitizer)
+AC_ARG_WITH(undefined_behavior_sanitizer,
+            AS_HELP_STRING([--with-undefined-behavior-sanitizer],
+                           [enable UndefinedBehaviorSanitizer (ubsan)]),
+[
+AC_MSG_RESULT($withval)
+BASECFLAGS="-fsanitize=undefined $BASECFLAGS"
+LDFLAGS="-fsanitize=undefined $LDFLAGS"
 ],
 [AC_MSG_RESULT(no)])