diff --git a/contrib/flex/buf.c b/contrib/flex/buf.c
index e5deb4e81c3a..fa713a69da98 100644
--- a/contrib/flex/buf.c
+++ b/contrib/flex/buf.c
@@ -90,7 +90,8 @@ struct Buf *buf_prints (struct Buf *buf, const char *fmt, const char *s)
  */
 struct Buf *buf_linedir (struct Buf *buf, const char* filename, int lineno)
 {
-    char *dst, *src, *t;
+    char *dst, *t;
+    const char *src;
 
     t = flex_alloc (strlen ("#line \"\"\n")          +   /* constant parts */
                     2 * strlen (filename)            +   /* filename with possibly all backslashes escaped */
diff --git a/contrib/flex/filter.c b/contrib/flex/filter.c
index c82f7f8938a1..b874e10cd063 100644
--- a/contrib/flex/filter.c
+++ b/contrib/flex/filter.c
@@ -135,9 +135,6 @@ struct filter *filter_create_int (struct filter *chain,
 bool filter_apply_chain (struct filter * chain)
 {
 	int     pid, pipes[2];
-	int     r;
-	const int readsz = 512;
-	char   *buf;
 
 
 	/* Tricky recursion, since we want to begin the chain
diff --git a/contrib/flex/flex.skl b/contrib/flex/flex.skl
index 8cf6356ad60c..3c5bac3a424a 100644
--- a/contrib/flex/flex.skl
+++ b/contrib/flex/flex.skl
@@ -196,7 +196,11 @@ m4_ifdef( [[M4_YY_TABLES_EXTERNAL]],
 /* First, we deal with  platform-specific or compiler-specific issues. */
 
 #if defined(__FreeBSD__)
+#ifndef __STDC_LIMIT_MACROS
+#define	__STDC_LIMIT_MACROS
+#endif
 #include <sys/cdefs.h>
+#include <stdint.h>
 #else
 #define	__dead2
 #endif
diff --git a/contrib/flex/flexint.h b/contrib/flex/flexint.h
index f9fa80cb08c0..c5502662ca3b 100644
--- a/contrib/flex/flexint.h
+++ b/contrib/flex/flexint.h
@@ -5,7 +5,8 @@
 
 /* C99 systems have <inttypes.h>. Non-C99 systems may or may not. */
 
-#if defined (__STDC_VERSION__) && __STDC_VERSION__ >= 199901L
+#if defined(__FreeBSD__) || \
+    (defined (__STDC_VERSION__) && __STDC_VERSION__ >= 199901L)
 
 /* C99 says to define __STDC_LIMIT_MACROS before including stdint.h,
  * if you want the limit (max/min) macros for int types. 
diff --git a/contrib/flex/gen.c b/contrib/flex/gen.c
index b99888d44109..1e554d4d5ee5 100644
--- a/contrib/flex/gen.c
+++ b/contrib/flex/gen.c
@@ -121,7 +121,7 @@ static struct yytbl_data *mkeoltbl (void)
 }
 
 /* Generate the table for possible eol matches. */
-static void geneoltbl ()
+static void geneoltbl (void)
 {
 	int     i;
 
@@ -431,7 +431,7 @@ void genctbl ()
 
 /* mkecstbl - Make equivalence-class tables.  */
 
-struct yytbl_data *mkecstbl (void)
+static struct yytbl_data *mkecstbl (void)
 {
 	int i;
 	struct yytbl_data *tbl = 0;
diff --git a/contrib/flex/libyywrap.c b/contrib/flex/libyywrap.c
index 8561a43f4cdd..7661e9121917 100644
--- a/contrib/flex/libyywrap.c
+++ b/contrib/flex/libyywrap.c
@@ -21,6 +21,7 @@
 /*  WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR */
 /*  PURPOSE. */
 
+int     yywrap (void);
 int     yywrap (void)
 {
 	return 1;
diff --git a/contrib/flex/main.c b/contrib/flex/main.c
index 069b7b228c6f..57b1f67ca23a 100644
--- a/contrib/flex/main.c
+++ b/contrib/flex/main.c
@@ -1575,11 +1575,12 @@ void readin ()
     }
 
 	if (!do_yywrap) {
-		if (!C_plus_plus)
+		if (!C_plus_plus) {
 			 if (reentrant)
 				outn ("\n#define yywrap(yyscanner) 1");
 			 else
 				outn ("\n#define yywrap() 1");
+		}
 		outn ("#define YY_SKIP_YYWRAP");
 	}
 
diff --git a/contrib/flex/misc.c b/contrib/flex/misc.c
index 5bc844f4342f..f9cb3775e7ad 100644
--- a/contrib/flex/misc.c
+++ b/contrib/flex/misc.c
@@ -113,6 +113,7 @@ void action_define (defname, value)
 }
 
 
+#ifdef notdef
 /** Append "m4_define([[defname]],[[value]])m4_dnl\n" to the running buffer.
  *  @param defname The macro name.
  *  @param value The macro value, can be NULL, which is the same as the empty string.
@@ -133,6 +134,7 @@ void action_m4_define (const char *defname, const char * value)
 	snprintf (buf, sizeof(buf), "m4_define([[%s]],[[%s]])m4_dnl\n", defname, value?value:"");
 	add_action (buf);
 }
+#endif
 
 /* Append "new_text" to the running buffer. */
 void add_action (new_text)
diff --git a/contrib/flex/scanflags.c b/contrib/flex/scanflags.c
index f75aa827de14..2c715e619b46 100644
--- a/contrib/flex/scanflags.c
+++ b/contrib/flex/scanflags.c
@@ -62,7 +62,7 @@ sf_init (void)
     _sf_stk = (scanflags_t*) flex_alloc ( sizeof(scanflags_t) * (_sf_max = 32));
     if (!_sf_stk)
         lerrsf_fatal(_("Unable to allocate %ld of stack"),
-            (long)sizeof(scanflags_t));
+            (void *)(uintptr_t)sizeof(scanflags_t));
     _sf_stk[_sf_top_ix] = 0;
 }