gc: test & fix handling of very long string constants

R=ken2
CC=golang-dev
https://golang.org/cl/207106

src/cmd/gc/lex.c

@@ -420,7 +420,7 @@ struct Loophack {
 static int32
 _yylex(void)
 {
-	int c, c1, clen, escflag;
+	int c, c1, clen, escflag, ncp;
 	vlong v;
 	char *cp;
 	Rune rune;
@@ -490,20 +490,22 @@ l0:
 	case '"':
 		/* "..." */
 		strcpy(lexbuf, "\"<string>\"");
-		cp = mal(sizeof(int32));
+		cp = mal(8);
 		clen = sizeof(int32);
+		ncp = 8;
 
 		for(;;) {
+			if(clen+UTFmax > ncp) {
+				cp = remal(cp, ncp, ncp);
+				ncp += ncp;
+			}
 			if(escchar('"', &escflag, &v))
 				break;
 			if(v < Runeself || escflag) {
-				cp = remal(cp, clen, 1);
 				cp[clen++] = v;
 			} else {
-				// botch - this limits size of runes
 				rune = v;
 				c = runelen(rune);
-				cp = remal(cp, clen, c);
 				runetochar(cp+clen, &rune);
 				clen += c;
 			}
@@ -513,10 +515,15 @@ l0:
 	case '`':
 		/* `...` */
 		strcpy(lexbuf, "`<string>`");
-		cp = mal(sizeof(int32));
+		cp = mal(8);
 		clen = sizeof(int32);
+		ncp = 8;
 
 		for(;;) {
+			if(clen == ncp) {
+				cp = remal(cp, clen, ncp);
+				ncp += ncp;
+			}
 			c = getc();
 			if(c == EOF) {
 				yyerror("eof in string");
@@ -524,14 +531,12 @@ l0:
 			}
 			if(c == '`')
 				break;
-			cp = remal(cp, clen, 1);
 			cp[clen++] = c;
 		}
 
 	strlit:
 		*(int32*)cp = clen-sizeof(int32);	// length
 		do {
-			cp = remal(cp, clen, 1);
 			cp[clen++] = 0;
 		} while(clen & MAXALIGN);
 		yylval.val.u.sval = (Strlit*)cp;

src/cmd/gc/subr.c

@@ -364,7 +364,7 @@ importdot(Pkg *opkg, Node *pack)
 	}
 }
 
-void
+static void
 gethunk(void)
 {
 	char *h;
@@ -374,7 +374,7 @@ gethunk(void)
 	if(thunk >= 10L*NHUNK)
 		nh = 10L*NHUNK;
 	h = (char*)malloc(nh);
-	if(h == (char*)-1) {
+	if(h == nil) {
 		flusherrors();
 		yyerror("out of memory");
 		errorexit();
@@ -389,11 +389,22 @@ mal(int32 n)
 {
 	void *p;
 
+	if(n >= NHUNK) {
+		p = malloc(n);
+		if(p == nil) {
+			flusherrors();
+			yyerror("out of memory");
+			errorexit();
+		}
+		memset(p, 0, n);
+		return p;
+	}
+
 	while((uintptr)hunk & MAXALIGN) {
 		hunk++;
 		nhunk--;
 	}
-	while(nhunk < n)
+	if(nhunk < n)
 		gethunk();
 
 	p = hunk;
@@ -410,7 +421,12 @@ remal(void *p, int32 on, int32 n)
 
 	q = (uchar*)p + on;
 	if(q != hunk || nhunk < n) {
-		while(nhunk < on+n)
+		if(on+n >= NHUNK) {
+			q = mal(on+n);
+			memmove(q, p, on);
+			return q;
+		}
+		if(nhunk < on+n)
 			gethunk();
 		memmove(hunk, p, on);
 		p = hunk;