"extern int errno" is just a really bad idea.


diff -Naur 5.5_orig/include/my_sys.h 5.5/include/my_sys.h
--- 5.5_orig/include/my_sys.h	2011-12-16 17:21:58.651149000 +0100
+++ 5.5/include/my_sys.h	2011-12-16 18:10:28.607900650 +0100
@@ -198,13 +198,8 @@
 #define my_safe_alloca(size, min_length) ((size <= min_length) ? my_alloca(size) : my_malloc(size,MYF(MY_FAE)))
 #define my_safe_afree(ptr, size, min_length) ((size <= min_length) ? my_afree(ptr) : my_free(ptr))
 
-#ifndef errno				/* did we already get it? */
-#ifdef HAVE_ERRNO_AS_DEFINE
 #include <errno.h>			/* errno is a define */
-#else
-extern int errno;			/* declare errno */
-#endif
-#endif					/* #ifndef errno */
+
 extern char *home_dir;			/* Home directory for user */
 extern MYSQL_PLUGIN_IMPORT char  *mysql_data_home;
 extern const char *my_progname;		/* program-name (printed in errors) */
 extern const char *my_progname_short;	/* like above but without directory */