diff --git a/changes/bug5969_022 b/changes/bug5969_022
new file mode 100644
index 0000000000..57c8744267
--- /dev/null
+++ b/changes/bug5969_022
@@ -0,0 +1,7 @@
+  o Minor bugfixes
+    - Fix a build warning with Clang 3.1 related to our use of vasprint.
+      Fix for bug 5969. Bugfix on 0.2.2.11-alpha.
+
+  o Compilation improvements:
+    - Tell GCC and Clang to check for any errors in format strings passed
+      to the tor_v*(print|scan)f functions.
diff --git a/src/common/compat.h b/src/common/compat.h
index b0ef63badf..7edd889ee3 100644
--- a/src/common/compat.h
+++ b/src/common/compat.h
@@ -259,11 +259,12 @@ void tor_munmap_file(tor_mmap_t *handle) ATTR_NONNULL((1));
 int tor_snprintf(char *str, size_t size, const char *format, ...)
   CHECK_PRINTF(3,4) ATTR_NONNULL((1,3));
 int tor_vsnprintf(char *str, size_t size, const char *format, va_list args)
-  ATTR_NONNULL((1,3));
+  CHECK_PRINTF(3,0) ATTR_NONNULL((1,3));
 
 int tor_asprintf(char **strp, const char *fmt, ...)
   CHECK_PRINTF(2,3);
-int tor_vasprintf(char **strp, const char *fmt, va_list args);
+int tor_vasprintf(char **strp, const char *fmt, va_list args)
+  CHECK_PRINTF(2,0);
 
 const void *tor_memmem(const void *haystack, size_t hlen, const void *needle,
                        size_t nlen) ATTR_NONNULL((1,3));
diff --git a/src/common/log.c b/src/common/log.c
index df27066f92..f509ddcd6e 100644
--- a/src/common/log.c
+++ b/src/common/log.c
@@ -137,6 +137,13 @@ static void close_log(logfile_t *victim);
 
 static char *domain_to_string(log_domain_mask_t domain,
                              char *buf, size_t buflen);
+static INLINE char *format_msg(char *buf, size_t buf_len,
+           log_domain_mask_t domain, int severity, const char *funcname,
+           const char *format, va_list ap, size_t *msg_len_out)
+  CHECK_PRINTF(6,0);
+static void logv(int severity, log_domain_mask_t domain, const char *funcname,
+                 const char *format, va_list ap)
+  CHECK_PRINTF(4,0);
 
 /** Name of the application: used to generate the message we write at the
  * start of each new log. */
diff --git a/src/common/util.h b/src/common/util.h
index 567efaafef..36601fa790 100644
--- a/src/common/util.h
+++ b/src/common/util.h
@@ -213,7 +213,11 @@ const char *escaped(const char *string);
 struct smartlist_t;
 void wrap_string(struct smartlist_t *out, const char *string, size_t width,
                  const char *prefix0, const char *prefixRest);
-int tor_vsscanf(const char *buf, const char *pattern, va_list ap);
+int tor_vsscanf(const char *buf, const char *pattern, va_list ap)
+#ifdef __GNUC__
+  __attribute__((format(scanf, 2, 0)))
+#endif
+  ;
 int tor_sscanf(const char *buf, const char *pattern, ...)
 #ifdef __GNUC__
   __attribute__((format(scanf, 2, 3)))
diff --git a/src/or/control.c b/src/or/control.c
index 1bba2e18de..91d94fd665 100644
--- a/src/or/control.c
+++ b/src/or/control.c
@@ -136,6 +136,13 @@ typedef int event_format_t;
 static void connection_printf_to_buf(control_connection_t *conn,
                                      const char *format, ...)
   CHECK_PRINTF(2,3);
+static void send_control_event_impl(uint16_t event, event_format_t which,
+                                    const char *format, va_list ap)
+  CHECK_PRINTF(3,0);
+static int control_event_status(int type, int severity, const char *format,
+                                va_list args)
+  CHECK_PRINTF(3,0);
+
 static void send_control_done(control_connection_t *conn);
 static void send_control_event(uint16_t event, event_format_t which,
                                const char *format, ...)
@@ -4208,6 +4215,7 @@ control_event_my_descriptor_changed(void)
 static int
 control_event_status(int type, int severity, const char *format, va_list args)
 {
+  char *user_buf = NULL;
   char format_buf[160];
   const char *status, *sev;
 
@@ -4239,13 +4247,15 @@ control_event_status(int type, int severity, const char *format, va_list args)
       log_warn(LD_BUG, "Unrecognized status severity %d", severity);
       return -1;
   }
-  if (tor_snprintf(format_buf, sizeof(format_buf), "650 %s %s %s\r\n",
-                   status, sev, format)<0) {
+  if (tor_snprintf(format_buf, sizeof(format_buf), "650 %s %s\r\n",
+                   status, sev)<0) {
     log_warn(LD_BUG, "Format string too long.");
     return -1;
   }
+  tor_vasprintf(&user_buf, format, args);
 
-  send_control_event_impl(type, ALL_FORMATS, format_buf, args);
+  send_control_event(type, ALL_FORMATS, "%s %s", format_buf, user_buf);
+  tor_free(user_buf);
   return 0;
 }