Index: configure.in
===================================================================
--- configure.in	(revision 61828)
+++ configure.in	(working copy)
@@ -2232,6 +2232,19 @@ then
 fi
 AC_MSG_RESULT($with_pymalloc)
 
+# Check for Valgrind support
+AC_MSG_CHECKING([for --with-valgrind])
+AC_ARG_WITH([valgrind],
+  AC_HELP_STRING([--with-valgrind], [Enable Valgrind support]),,
+  with_valgrind=no)
+AC_MSG_RESULT([$with_valgrind])
+if test "$with_valgrind" != no; then
+    AC_CHECK_HEADER([valgrind/valgrind.h],
+      [AC_DEFINE([WITH_VALGRIND], 1, [Define if you want pymalloc to be disabled when running under valgrind])],
+      [AC_MSG_ERROR([Valgrind support requested but headers not available])]
+    )
+fi
+
 # Check for --with-wctype-functions
 AC_MSG_CHECKING(for --with-wctype-functions)
 AC_ARG_WITH(wctype-functions, 
Index: Objects/obmalloc.c
===================================================================
--- Objects/obmalloc.c	(revision 61828)
+++ Objects/obmalloc.c	(working copy)
@@ -2,6 +2,21 @@
 
 #ifdef WITH_PYMALLOC
 
+#ifdef WITH_VALGRIND
+#include <valgrind/valgrind.h>
+
+/* If we're using GCC, use __builtin_expect() to reduce overhead of
+   the valgrind checks */
+#if defined(__GNUC__) && (__GNUC__ > 2) && defined(__OPTIMIZE__)
+#  define UNLIKELY(value) __builtin_expect((value), 0)
+#else
+#  define UNLIKELY(value) (value)
+#endif
+
+/* -1 indicates that we haven't checked that we're running on valgrind yet. */
+static int running_on_valgrind = -1;
+#endif
+
 /* An object allocator for Python.
 
    Here is an introduction to the layers of the Python memory architecture,
@@ -726,6 +741,13 @@ PyObject_Malloc(size_t nbytes)
 	poolp next;
 	uint size;
 
+#ifdef WITH_VALGRIND
+	if (UNLIKELY(running_on_valgrind == -1))
+		running_on_valgrind = RUNNING_ON_VALGRIND;
+	if (UNLIKELY(running_on_valgrind))
+		goto redirect;
+#endif
+
 	/*
 	 * This implicitly redirects malloc(0).
 	 */
@@ -916,6 +938,11 @@ PyObject_Free(void *p)
 	if (p == NULL)	/* free(NULL) has no effect */
 		return;
 
+#ifdef WITH_VALGRIND
+	if (UNLIKELY(running_on_valgrind > 0))
+		goto redirect;
+#endif
+
 	pool = POOL_ADDR(p);
 	if (Py_ADDRESS_IN_RANGE(p, pool)) {
 		/* We allocated this address. */
@@ -1110,6 +1137,7 @@ PyObject_Free(void *p)
 		return;
 	}
 
+redirect:
 	/* We didn't allocate this address. */
 	free(p);
 }
@@ -1130,6 +1158,12 @@ PyObject_Realloc(void *p, size_t nbytes)
 	if (p == NULL)
 		return PyObject_Malloc(nbytes);
 
+#ifdef WITH_VALGRIND
+	/* Treat running_on_valgrind == -1 the same as 0 */
+	if (UNLIKELY(running_on_valgrind > 0))
+		goto redirect;
+#endif
+
 	pool = POOL_ADDR(p);
 	if (Py_ADDRESS_IN_RANGE(p, pool)) {
 		/* We're in charge of this block */
@@ -1157,6 +1191,7 @@ PyObject_Realloc(void *p, size_t nbytes)
 		}
 		return bp;
 	}
+ redirect:
 	/* We're not managing this block.  If nbytes <=
 	 * SMALL_REQUEST_THRESHOLD, it's tempting to try to take over this
 	 * block.  However, if we do, we need to copy the valid data from
Index: Misc/NEWS
===================================================================
--- Misc/NEWS	(revision 61828)
+++ Misc/NEWS	(working copy)
@@ -60,6 +60,11 @@ Core and builtins
 
 - Issue #2143: Fix embedded readline() hang on SSL socket EOF.
 
+- Issue #2422: When compiled with the ``--with-valgrind`` option, the
+  pymalloc allocator will be automatically disabled when running under
+  Valgrind.  This gives improved memory leak detection when running
+  under Valgrind, while taking advantage of pymalloc at other times.
+
 Library
 -------
 
Index: pyconfig.h.in
===================================================================
--- pyconfig.h.in	(revision 61828)
+++ pyconfig.h.in	(working copy)
@@ -958,6 +958,9 @@
 /* Define to profile with the Pentium timestamp counter */
 #undef WITH_TSC
 
+/* Define if you want pymalloc to be disabled when running under valgrind */
+#undef WITH_VALGRIND
+
 
  /* Define to 1 if your processor stores words with the most significant byte
     first (like Motorola and SPARC, unlike Intel and VAX).