diff --git a/doc/jemalloc.xml.in b/doc/jemalloc.xml.in
index 19afe362..f283fd37 100644
--- a/doc/jemalloc.xml.in
+++ b/doc/jemalloc.xml.in
@@ -1760,7 +1760,16 @@ malloc_conf = "xmalloc:true";]]></programlisting>
         automatically managed one that is used by default.  Each explicit cache
         can be used by only one thread at a time; the application must assure
         that this constraint holds.
+        </para>
+
+        <para>If the amount of space supplied for storing the thread-specific
+        cache identifier does not equal
+        <code language="C">sizeof(<type>unsigned</type>)</code>, no
+        thread-specific cache will be created, no data will be written to the
+        space pointed by <parameter>oldp</parameter>, and
+        <parameter>*oldlenp</parameter> will be set to 0.
         </para></listitem>
+
       </varlistentry>
 
       <varlistentry id="tcache.flush">
@@ -2300,7 +2309,14 @@ struct extent_hooks_s {
         </term>
         <listitem><para>Explicitly create a new arena outside the range of
         automatically managed arenas, with optionally specified extent hooks,
-        and return the new arena index.</para></listitem>
+        and return the new arena index.</para>
+
+        <para>If the amount of space supplied for storing the arena index does
+        not equal <code language="C">sizeof(<type>unsigned</type>)</code>, no
+        arena will be created, no data will be written to the space pointed by
+        <parameter>oldp</parameter>, and <parameter>*oldlenp</parameter> will
+        be set to 0.
+        </para></listitem>
       </varlistentry>
 
       <varlistentry id="arenas.lookup">
@@ -3607,7 +3623,8 @@ MAPPED_LIBRARIES:
             <listitem><para><parameter>newp</parameter> is not
             <constant>NULL</constant>, and <parameter>newlen</parameter> is too
             large or too small.  Alternatively, <parameter>*oldlenp</parameter>
-            is too large or too small; in this case as much data as possible
+            is too large or too small; when it happens, except for a very few
+            cases explicitly documented otherwise, as much data as possible
             are read despite the error, with the amount of data read being
             recorded in <parameter>*oldlenp</parameter>.</para></listitem>
           </varlistentry>
diff --git a/src/ctl.c b/src/ctl.c
index 92e9f511..9cfb2588 100644
--- a/src/ctl.c
+++ b/src/ctl.c
@@ -1488,6 +1488,15 @@ ctl_mtx_assert_held(tsdn_t *tsdn) {
 	}								\
 } while (0)
 
+/* Verify that the space provided is enough. */
+#define VERIFY_READ(t)	do {						\
+	if (oldp == NULL || oldlenp == NULL || *oldlenp != sizeof(t)) {	\
+		*oldlenp = 0;						\
+		ret = EINVAL;						\
+		goto label_return;					\
+	}								\
+} while (0)
+
 #define READ(v, t)	do {						\
 	if (oldp != NULL && oldlenp != NULL) {				\
 		if (*oldlenp != sizeof(t)) {				\
@@ -1559,8 +1568,8 @@ label_return:								\
 
 #define CTL_RO_CGEN(c, n, v, t)						\
 static int								\
-n##_ctl(tsd_t *tsd, const size_t *mib, size_t miblen, \
-    void *oldp, size_t *oldlenp, void *newp, size_t newlen) {			\
+n##_ctl(tsd_t *tsd, const size_t *mib, size_t miblen,			\
+    void *oldp, size_t *oldlenp, void *newp, size_t newlen) {		\
 	int ret;							\
 	t oldval;							\
 									\
@@ -1602,8 +1611,8 @@ label_return:								\
  */
 #define CTL_RO_NL_CGEN(c, n, v, t)					\
 static int								\
-n##_ctl(tsd_t *tsd, const size_t *mib, size_t miblen, \
-    void *oldp, size_t *oldlenp, void *newp, size_t newlen) {			\
+n##_ctl(tsd_t *tsd, const size_t *mib, size_t miblen,			\
+    void *oldp, size_t *oldlenp, void *newp, size_t newlen) {		\
 	int ret;							\
 	t oldval;							\
 									\
@@ -1621,8 +1630,8 @@ label_return:								\
 
 #define CTL_RO_NL_GEN(n, v, t)						\
 static int								\
-n##_ctl(tsd_t *tsd, const size_t *mib, size_t miblen, \
-    void *oldp, size_t *oldlenp, void *newp, size_t newlen) {			\
+n##_ctl(tsd_t *tsd, const size_t *mib, size_t miblen,			\
+    void *oldp, size_t *oldlenp, void *newp, size_t newlen) {		\
 	int ret;							\
 	t oldval;							\
 									\
@@ -1637,8 +1646,8 @@ label_return:								\
 
 #define CTL_RO_CONFIG_GEN(n, t)						\
 static int								\
-n##_ctl(tsd_t *tsd, const size_t *mib, size_t miblen, \
-    void *oldp, size_t *oldlenp, void *newp, size_t newlen) {			\
+n##_ctl(tsd_t *tsd, const size_t *mib, size_t miblen,			\
+    void *oldp, size_t *oldlenp, void *newp, size_t newlen) {		\
 	int ret;							\
 	t oldval;							\
 									\
@@ -2103,6 +2112,7 @@ tcache_create_ctl(tsd_t *tsd, const size_t *mib, size_t miblen,
 	unsigned tcache_ind;
 
 	READONLY();
+	VERIFY_READ(unsigned);
 	if (tcaches_create(tsd, b0get(), &tcache_ind)) {
 		ret = EFAULT;
 		goto label_return;
@@ -2608,10 +2618,6 @@ arenas_narenas_ctl(tsd_t *tsd, const size_t *mib, size_t miblen,
 
 	malloc_mutex_lock(tsd_tsdn(tsd), &ctl_mtx);
 	READONLY();
-	if (*oldlenp != sizeof(unsigned)) {
-		ret = EINVAL;
-		goto label_return;
-	}
 	narenas = ctl_arenas->narenas;
 	READ(narenas, unsigned);
 
@@ -2702,6 +2708,7 @@ arenas_create_ctl(tsd_t *tsd, const size_t *mib, size_t miblen,
 
 	malloc_mutex_lock(tsd_tsdn(tsd), &ctl_mtx);
 
+	VERIFY_READ(unsigned);
 	extent_hooks = (extent_hooks_t *)&ehooks_default_extent_hooks;
 	WRITE(extent_hooks, extent_hooks_t *);
 	if ((arena_ind = ctl_arena_init(tsd, extent_hooks)) == UINT_MAX) {
@@ -2731,12 +2738,14 @@ arenas_lookup_ctl(tsd_t *tsd, const size_t *mib,
 	malloc_mutex_lock(tsd_tsdn(tsd), &ctl_mtx);
 	WRITE(ptr, void *);
 	edata = emap_edata_lookup(tsd_tsdn(tsd), &arena_emap_global, ptr);
-	if (edata == NULL)
+	if (edata == NULL) {
 		goto label_return;
+	}
 
 	arena = arena_get_from_edata(edata);
-	if (arena == NULL)
+	if (arena == NULL) {
 		goto label_return;
+	}
 
 	arena_ind = arena_ind_get(arena);
 	READ(arena_ind, unsigned);