diff --git a/usr.bin/tar/bsdtar_platform.h b/usr.bin/tar/bsdtar_platform.h
index 6552a98aefb5..5ad8d30a584d 100644
--- a/usr.bin/tar/bsdtar_platform.h
+++ b/usr.bin/tar/bsdtar_platform.h
@@ -37,19 +37,18 @@
 #if defined(PLATFORM_CONFIG_H)
 /* Use hand-built config.h in environments that need it. */
 #include PLATFORM_CONFIG_H
-#elif defined(HAVE_CONFIG_H)
-/* Most POSIX platforms use the 'configure' script to build config.h */
+#else
+/* Not having a config.h of some sort is a serious problem. */
 #include "config.h"
-#else
-/* Warn if bsdtar hasn't been (automatically or manually) configured. */
-#error Oops: No config.h and no built-in configuration in bsdtar_platform.h.
-#endif /* !HAVE_CONFIG_H */
+#endif
 
-/* No non-FreeBSD platform will have __FBSDID, so just define it here. */
-#ifdef __FreeBSD__
-#include <sys/cdefs.h>  /* For __FBSDID */
-#else
-/* Just leaving this macro replacement empty leads to a dangling semicolon. */
+/* Get a real definition for __FBSDID if we can */
+#if HAVE_SYS_CDEFS_H
+#include <sys/cdefs.h>
+#endif
+
+/* If not, define it so as to avoid dangling semicolons. */
+#ifndef __FBSDID
 #define	__FBSDID(a)     struct _undefined_hack
 #endif
 
@@ -92,25 +91,6 @@
 # endif
 #endif
 
-
-/*
- * We need to be able to display a filesize using printf().  The type
- * and format string here must be compatible with one another and
- * large enough for any file.
- */
-#if HAVE_UINTMAX_T
-#define	BSDTAR_FILESIZE_TYPE	uintmax_t
-#define	BSDTAR_FILESIZE_PRINTF	"%ju"
-#else
-#if HAVE_UNSIGNED_LONG_LONG
-#define	BSDTAR_FILESIZE_TYPE	unsigned long long
-#define	BSDTAR_FILESIZE_PRINTF	"%llu"
-#else
-#define	BSDTAR_FILESIZE_TYPE	unsigned long
-#define	BSDTAR_FILESIZE_PRINTF	"%lu"
-#endif
-#endif
-
 #if HAVE_STRUCT_STAT_ST_MTIMESPEC_TV_NSEC
 #define	ARCHIVE_STAT_CTIME_NANOS(st)	(st)->st_ctimespec.tv_nsec
 #define	ARCHIVE_STAT_MTIME_NANOS(st)	(st)->st_mtimespec.tv_nsec