diff --git a/modules/libcom/src/flex/Makefile b/modules/libcom/src/flex/Makefile
index 5c6f41bfe..9b98e33d5 100644
--- a/modules/libcom/src/flex/Makefile
+++ b/modules/libcom/src/flex/Makefile
@@ -19,7 +19,7 @@ parse_CPPFLAGS = -DDEFAULT_SKELETON_FILE=$(SKELETON_FILE)
 
 INC += flex.skel.static
 
-# flex.c is included in parse.c
+# flex.c, scan.c and yylex.c are #included by parse.c
 e_flex_SRCS += ccl.c
 e_flex_SRCS += dfa.c
 e_flex_SRCS += ecs.c
diff --git a/modules/libcom/src/flex/ccl.c b/modules/libcom/src/flex/ccl.c
index 4d278ba2a..48a2ccc57 100644
--- a/modules/libcom/src/flex/ccl.c
+++ b/modules/libcom/src/flex/ccl.c
@@ -132,7 +132,6 @@ void cclnegate(int cclp)
 void list_character_set(FILE *file, int cset[])
 {
     int i;
-    char *readable_form();
 
     putc( '[', file );
 
diff --git a/modules/libcom/src/flex/flex.c b/modules/libcom/src/flex/flex.c
index 79ea51dda..349d8aff3 100644
--- a/modules/libcom/src/flex/flex.c
+++ b/modules/libcom/src/flex/flex.c
@@ -188,7 +188,6 @@ int main(int argc, char *argv[])
 void flexend(int status)
 {
     int tblsiz;
-    char *flex_gettime();
 
     if ( skelfile != NULL )
         {
@@ -382,7 +381,7 @@ void flexend(int status)
 void flexinit(int argc, char **argv)
 {
     int i, sawcmpflag;
-    char *arg, *flex_gettime(), *mktemp();
+    char *arg;
 
     printstats = syntaxerror = trace = spprdflt = interactive = caseins = false;
     backtrack_report = performance_report = ddebug = fulltbl = fullspd = false;
diff --git a/modules/libcom/src/flex/flexdef.h b/modules/libcom/src/flex/flexdef.h
index 0a9736e6c..dd6123da2 100644
--- a/modules/libcom/src/flex/flexdef.h
+++ b/modules/libcom/src/flex/flexdef.h
@@ -567,8 +567,8 @@ extern int sectnum, nummt, hshcol, dfaeql, numeps, eps2, num_reallocs;
 extern int tmpuses, totnst, peakpairs, numuniq, numdup, hshsave;
 extern int num_backtracking, bol_needed;
 
-void *allocate_array(int size, int element_size);
-void *reallocate_array(void *array, int size, int element_size);
+extern void *allocate_array(int size, int element_size);
+extern void *reallocate_array(void *array, int size, int element_size);
 
 #define allocate_integer_array(size) \
     (int *) allocate_array( size, sizeof( int ) )
@@ -677,10 +677,20 @@ extern int all_upper (Char *);
 /* bubble sort an integer array */
 extern void bubble (int [], int);
 
+/* replace upper-case letter to lower-case */
+extern Char clower(int c);
+
+/* returns copy of a string */
+extern char *copy_string(char *str);
+
+/* returns copy of a (potentially) unsigned string */
+extern Char *copy_unsigned_string(Char *str);
+
 /* shell sort a character array */
 extern void cshell (Char [], int, int);
 
-extern void dataend (void);     /* finish up a block of data declarations */
+/* finish up a block of data declarations */
+extern void dataend (void);
 
 /* report an error message and terminate */
 extern void flexerror (char[]) NORETURN;
@@ -688,6 +698,9 @@ extern void flexerror (char[]) NORETURN;
 /* report a fatal error message and terminate */
 extern void flexfatal (char[]);
 
+/* return current time */
+extern char *flex_gettime();
+
 /* report an error message formatted with one integer argument */
 extern void lerrif (char[], int);
 
@@ -700,11 +713,18 @@ extern void line_directive_out (FILE*);
 /* generate a data statment for a two-dimensional array */
 extern void mk2data (int);
 
-extern void mkdata (int);       /* generate a data statement */
+/* generate a data statement */
+extern void mkdata (int);
 
 /* return the integer represented by a string of digits */
 extern int myctoi (Char []);
 
+/* return character corresponding to escape sequence */
+extern Char myesc(Char *array);
+
+/* return the the human-readable form of a character */
+extern char *readable_form(int c);
+
 /* write out one section of the skeleton file */
 extern void skelout (void);
 
@@ -784,8 +804,14 @@ extern void cclinstal (Char [], int);
 /* lookup the number associated with character class */
 extern int ccllookup (Char []);
 
-extern void ndinstal (char[], Char[]);  /* install a name definition */
-extern void scinstal (char[], int);     /* make a start condition */
+/* install a name definition */
+extern void ndinstal (char[], Char[]);
+
+/* lookup a name definition */
+extern Char *ndlookup(char *nd);
+
+/* make a start condition */
+extern void scinstal (char[], int);
 
 /* lookup the number associated with a start condition */
 extern int sclookup (char[]);
diff --git a/modules/libcom/src/flex/gen.c b/modules/libcom/src/flex/gen.c
index a10fbb537..f683d136c 100644
--- a/modules/libcom/src/flex/gen.c
+++ b/modules/libcom/src/flex/gen.c
@@ -217,7 +217,6 @@ void genecs(void)
     int i, j;
     static char C_char_decl[] = "static const %s %s[%d] =\n    {   0,\n";
     int numrows;
-    Char clower();
 
     if ( numecs < csize )
         printf( C_char_decl, "YY_CHAR", "yy_ec", csize );
@@ -237,8 +236,6 @@ void genecs(void)
 
     if ( trace )
         {
-        char *readable_form();
-
         fputs( "\n\nEquivalence Classes:\n\n", stderr );
 
         numrows = csize / 8;
diff --git a/modules/libcom/src/flex/parse.y b/modules/libcom/src/flex/parse.y
index 21ac91730..09aebc5b3 100644
--- a/modules/libcom/src/flex/parse.y
+++ b/modules/libcom/src/flex/parse.y
@@ -34,11 +34,18 @@
 
 int pat, scnum, eps, headcnt, trailcnt, anyccl, lastchar, i, actvp, rulelen;
 int trlcontxt, xcluflg, cclsorted, varlength, variable_trail_rule;
-Char clower();
 
 static int madeany = false;  /* whether we've made the '.' character class */
 int previous_continued_action;  /* whether the previous rule's action was '|' */
 
+/* forward declarations */
+
+void build_eof_action( void );
+void synerr( char str[] );
+void format_pinpoint_message( char msg[], char arg[] );
+void pinpoint_message( char str[] );
+void yyerror( char msg[] );
+
 %}
 
 %%
@@ -626,7 +633,7 @@ string          :  string CHAR
  *                    conditions
  */
 
-void build_eof_action()
+void build_eof_action( void )
 
     {
     int i;
@@ -652,8 +659,7 @@ void build_eof_action()
 
 /* synerr - report a syntax error */
 
-void synerr( str )
-char str[];
+void synerr( char str[] )
 
     {
     syntaxerror = true;
@@ -665,8 +671,7 @@ char str[];
  *                           pinpointing its location
  */
 
-void format_pinpoint_message( msg, arg )
-char msg[], arg[];
+void format_pinpoint_message( char msg[], char arg[] )
 
     {
     char errmsg[MAXLINE];
@@ -678,8 +683,7 @@ char msg[], arg[];
 
 /* pinpoint_message - write out a message, pinpointing its location */
 
-void pinpoint_message( str )
-char str[];
+void pinpoint_message( char str[] )
 
     {
     fprintf( stderr, "\"%s\", line %d: %s\n", infilename, linenum, str );
@@ -690,8 +694,7 @@ char str[];
  *           currently, messages are ignore
  */
 
-void yyerror( msg )
-char msg[];
+void yyerror( char msg[] )
 
     {
     }
diff --git a/modules/libcom/src/flex/scan.c b/modules/libcom/src/flex/scan.c
index 67c6be38c..e1fd68eb3 100644
--- a/modules/libcom/src/flex/scan.c
+++ b/modules/libcom/src/flex/scan.c
@@ -953,6 +953,7 @@ void yy_load_buffer_state ( void );
 YY_BUFFER_STATE yy_create_buffer ( FILE *file, int size );
 void yy_delete_buffer ( YY_BUFFER_STATE b );
 void yy_init_buffer ( YY_BUFFER_STATE b, FILE *file );
+void set_input_file( char *file );
 
 #define yy_new_buffer yy_create_buffer
 
@@ -966,7 +967,7 @@ YY_DECL
     static int bracelevel, didadef;
     int i, indented_code = false, checking_used = false, new_xlation = false;
     int doing_codeblock = false;
-    Char nmdef[MAXLINE], myesc();
+    Char nmdef[MAXLINE];
 
 
     if ( yy_init )
@@ -1488,7 +1489,6 @@ case 65:
 # line 333 "scan.l"
 {
                         Char *nmdefptr;
-                        Char *ndlookup();
 
                         (void) strcpy( nmstr, (char *) yytext );
                         nmstr[yyleng - 1] = '\0';  /* chop trailing brace */
@@ -2230,8 +2230,7 @@ int yywrap()
 
 /* set_input_file - open the given file (if NULL, stdin) for scanning */
 
-void set_input_file( file )
-char *file;
+void set_input_file( char *file )
 
     {
     if ( file )
diff --git a/modules/libcom/src/flex/sym.c b/modules/libcom/src/flex/sym.c
index e17d59427..59dac35d8 100644
--- a/modules/libcom/src/flex/sym.c
+++ b/modules/libcom/src/flex/sym.c
@@ -108,8 +108,6 @@ void cclinstal(Char *ccltxt, int cclnum)
     /* we don't bother checking the return status because we are not called
      * unless the symbol is new
      */
-    Char *copy_unsigned_string();
-
     (void) addsym( (char *) copy_unsigned_string( ccltxt ), (char *) 0, cclnum,
                    ccltab, CCL_HASH_SIZE );
     }
@@ -191,9 +189,6 @@ int hashfunct(char *str, int hash_size)
 
 void ndinstal(char *nd, Char *def)
 {
-    char *copy_string();
-    Char *copy_unsigned_string();
-
     if ( addsym( copy_string( nd ), (char *) copy_unsigned_string( def ), 0,
                  ndtbl, NAME_TABLE_HASH_SIZE ) )
         synerr( "name defined twice" );
@@ -227,8 +222,6 @@ Char *ndlookup(char *nd)
 
 void scinstal(char *str, int xcluflg)
 {
-    char *copy_string();
-
     /* bit of a hack.  We know how the default start-condition is
      * declared, and don't put out a define for it, because it
      * would come out as "#define 0 1"