Grammar optimization from NetBSD: Two adjacent string constants are merged.

FIXES

@@ -25,12 +25,17 @@ THIS SOFTWARE.
 This file lists all bug fixes, changes, etc., made since the AWK book
 was sent to the printers in August, 1987.
 
+July 28, 2019:
+	Import grammar optimization from NetBSD: Two string constants
+	concatenated together get turned into a single string.
+
 July 26, 2019:
 	Support POSIX-specified C-style escape sequences "\a" (alarm)
 	and "\v" (vertical tab) in command line arguments and regular
 	expressions, further to the support for them in strings added on
 	Apr 9, 1989. These now no longer match as literal "a" and "v"
 	characters (as they don't on other awk implementations).
+	Thanks to Martijn Dekker.
 
 July 17, 2019:
 	Pull in a number of code cleanups and minor fixes from

awkgram.y

@@ -71,6 +71,7 @@ Node	*arglist = 0;	/* list of args for current function */
 %type	<i>	do st
 %type	<i>	pst opt_pst lbrace rbrace rparen comma nl opt_nl and bor
 %type	<i>	subop print
+%type	<cp>	string
 
 %right	ASGNOP
 %right	'?'
@@ -348,6 +349,11 @@ subop:
 	  SUB | GSUB
 	;
 
+string:
+	  STRING
+	| string STRING		{ $$ = catstr($1, $2); }
+	;
+
 term:
  	  term '/' ASGNOP term		{ $$ = op2(DIVEQ, $1, $4); }
  	| term '+' term			{ $$ = op2(ADD, $1, $3); }
@@ -394,7 +400,7 @@ term:
 	| SPLIT '(' pattern comma varname ')'
 		{ $$ = op4(SPLIT, $3, makearr($5), NIL, (Node*)STRING); }  /* default */
 	| SPRINTF '(' patlist ')'	{ $$ = op1($1, $3); }
-	| STRING	 		{ $$ = celltonode($1, CCON); }
+	| string	 		{ $$ = celltonode($1, CCON); }
 	| subop '(' reg_expr comma pattern ')'
 		{ $$ = op4($1, NIL, (Node*)makedfa($3, 1), $5, rectonode()); }
 	| subop '(' pattern comma pattern ')'

main.c

@@ -22,7 +22,7 @@ ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF
 THIS SOFTWARE.
 ****************************************************************/
 
-const char	*version = "version 20190726";
+const char	*version = "version 20190728";
 
 #define DEBUG
 #include <stdio.h>

proto.h

@@ -111,6 +111,7 @@ extern	char	*getsval(Cell *);
 extern	char	*getpssval(Cell *);     /* for print */
 extern	char	*tostring(const char *);
 extern	char	*qstring(const char *, int);
+extern	Cell	*catstr(Cell *, Cell *);
 
 extern	void	recinit(unsigned int);
 extern	void	initgetrec(void);

tran.c

@@ -516,6 +516,22 @@ char *tostring(const char *s)	/* make a copy of string s */
 	return(p);
 }
 
+Cell *catstr(Cell *a, Cell *b) /* concatenate a and b */
+{
+	Cell *c;
+	char *p;
+	char *sa = getsval(a);
+	char *sb = getsval(b);
+	size_t l = strlen(sa) + strlen(sb) + 1;
+	p = malloc(l);
+	if (p == NULL)
+		FATAL("out of space concatenating %s and %s", sa, sb);
+	snprintf(p, l, "%s%s", sa, sb);
+	c = setsymtab(p, p, 0.0, CON|STR|DONTFREE, symtab);
+	free(p);
+	return c;
+}
+
 char *qstring(const char *is, int delim)	/* collect string up to next delim */
 {
 	const char *os = is;