Amir Shalem writes:

there is a missing include for <bits/uClibc_uintmaxtostr.h> in 
libc/string/_syserrmsg.h, where _syserrmsg.h uses __UIM_BUFLEN_INT

libc/string/__xpg_strerror_r.c

@@ -8,7 +8,6 @@
 #include <features.h>
 #include <errno.h>
 #include <string.h>
-#include <bits/uClibc_uintmaxtostr.h>
 #include "_syserrmsg.h"
 
 libc_hidden_proto(__xpg_strerror_r)

libc/string/_syserrmsg.h

@@ -8,6 +8,8 @@
 #ifndef __SYSERRMSG_H
 #define __SYSERRMSG_H 1
 
+#include <bits/uClibc_uintmaxtostr.h>
+
 /**********************************************************************/
 /* NOTE: If we ever do internationalized syserr messages, this will
  * have to be changed! */