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Avoid call to strlen in expand()

We know the size of the expanded string in all the cases,
so it is better to avoid the cll to strlen. We also know that
BUFSIZ is at least 509 bytes, so the calls to snprintf can be
substituted by sprintf

--- a/cc1/cpp.c

+++ b/cc1/cpp.c

@@ -139,10 +139,10 @@

 	return 1;

 }

-static void

-copymacro(char *bp, char *s, size_t bufsiz, char *arglist[])

+static size_t

+copymacro(char *buffer, char *s, size_t bufsiz, char *arglist[])

 {

-	char prevc, c, *arg;

+	char prevc, c, *arg, *bp = buffer;

 	for (prevc = '\0'; c = *s; prevc = c, ++s) {

 		if (c != '@') {

@@ -172,7 +172,7 @@

 	}

 	*bp = '\0';

-	return;

+	return bp - buffer;

 expansion_too_long:

 	error("expansion of macro \"%s\" is too long", macroname);

@@ -183,22 +183,17 @@

 expand(char *begin, Symbol *sym)

 {

 	size_t total, elen, rlen, llen, ilen;

-	int n, r;

+	int n;

 	char *s = sym->u.s;

 	char *arglist[NR_MACROARG], arguments[INPUTSIZ], buffer[BUFSIZE];

 	if (sym == symfile) {

-		sprintf(buffer, "\"%s\"", input->fname);

-		goto print_subs;

+		elen = sprintf(buffer, "\"%s\"", input->fname);

+		goto substitute;

 	}

 	if (sym == symline) {

-		r = snprintf(buffer, sizeof(buffer), "%d", input->nline);

-		if(r == -1 || (size_t)r >= sizeof(buffer)) {

-			error("expansion of macro \"%s\" is too long", sym->name);

-			return 0;

-		}

-		fprintf(stderr, "Expansion of line '%s'\n", buffer);

-		goto print_subs;

+		elen = sprintf(buffer, "%d", input->nline);

+		goto substitute;

 	}

 	macroname = sym->name;

@@ -207,11 +202,10 @@

 	for (n = 0; n < atoi(s); ++n)

 		fprintf(stderr, "PAR%d:%s\n", n, arglist[n]);

-	copymacro(buffer, s+3, INPUTSIZ-1, arglist);

+	elen = copymacro(buffer, s+3, INPUTSIZ-1, arglist);

-print_subs:

+substitute:

 	fprintf(stderr, "macro '%s' expanded to :'%s'\n", macroname, buffer);

-	elen = strlen(buffer);        /* expansion lentgh */

 	rlen = strlen(input->p);      /* rigth length */

 	llen = begin - input->line;   /* left length */

 	ilen = input->p - begin;      /* invocation length */