ld: grow dwarf includestack on demand.

Fixes #2241
while not breaking issue 1878 again.

R=rsc
CC=golang-dev
https://golang.org/cl/4988048

src/cmd/gc/obj.c

@@ -125,7 +125,6 @@ static void
 outhist(Biobuf *b)
 {
 	Hist *h;
-	int i, depth = 0;
 	char *p, ds[] = {'c', ':', '/', 0};
 
 	for(h = hist; h != H; h = h->link) {
@@ -162,14 +161,7 @@ outhist(Biobuf *b)
 					outzfile(b, p);
 				}
 			}
-			if(h->offset > 0) {
-				//line directive
-				depth++;
-			}
-		} else if(depth > 0) {
-			for(i = 0; i < depth; i++)
-				zhist(b, h->line, h->offset);
-			depth = 0;
+		
 		}
 		zhist(b, h->line, h->offset);
 	}

src/cmd/ld/dwarf.c

@@ -1578,13 +1578,16 @@ addhistfile(char *zentry)
 		histfile[histfilesize++] = "<eof>";
 
 	fname = decodez(zentry);
+//	print("addhistfile %d: %s\n", histfilesize, fname);
 	if (fname == 0)
 		return -1;
+
 	// Don't fill with duplicates (check only top one).
 	if (strcmp(fname, histfile[histfilesize-1]) == 0) {
 		free(fname);
 		return histfilesize - 1;
 	}
+
 	histfile[histfilesize++] = fname;
 	return histfilesize - 1;
 }
@@ -1608,11 +1611,13 @@ finddebugruntimepath(void)
 }
 
 // Go's runtime C sources are sane, and Go sources nest only 1 level,
-// so 16 should be plenty.
+// so a handful would be plenty, if it weren't for the fact that line
+// directives can push an unlimited number of them.
 static struct {
 	int file;
 	vlong line;
-} includestack[16];
+} *includestack;
+static int includestacksize;
 static int includetop;
 static vlong absline;
 
@@ -1629,17 +1634,15 @@ static Linehist *linehist;
 static void
 checknesting(void)
 {
-	int i;
-
 	if (includetop < 0) {
 		diag("dwarf: corrupt z stack");
 		errorexit();
 	}
-	if (includetop >= nelem(includestack)) {
-		diag("dwarf: nesting too deep");
-		for (i = 0; i < nelem(includestack); i++)
-			diag("\t%s", histfile[includestack[i].file]);
-		errorexit();
+	if (includetop >= includestacksize) {
+		includestacksize += 1;
+		includestacksize <<= 2;
+//		print("checknesting: growing to %d\n", includestacksize);
+		includestack = realloc(includestack, includestacksize * sizeof *includestack);	       
 	}
 }
 
@@ -1669,6 +1672,7 @@ inithist(Auto *a)
 	// Clear the history.
 	clearhistfile();
 	includetop = 0;
+	checknesting();
 	includestack[includetop].file = 0;
 	includestack[includetop].line = -1;
 	absline = 0;
@@ -1682,10 +1686,10 @@ inithist(Auto *a)
 	for (; a; a = a->link) {
 		if (a->type == D_FILE) {  // 'z'
 			int f = addhistfile(a->asym->name);
-			if (f < 0) {	   // pop file
+			if (f < 0) {	// pop file
 				includetop--;
 				checknesting();
-			} else if(f != includestack[includetop].file) { // pushed a new file
+			} else {	// pushed a file (potentially same)
 				includestack[includetop].line += a->aoffset - absline;
 				includetop++;
 				checknesting();

test/dwarf/linedirectives.go

+// $G $D/$F.go && $L $F.$A && ./$A.out
+
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//line foo/bar.y:4
+package main
+//line foo/bar.y:60
+func main() { 
+//line foo/bar.y:297
+	f, l := 0, 0
+//line yacctab:1
+	f, l = 1, 1
+//line yaccpar:1
+	f, l = 2, 1
+//line foo/bar.y:82
+	f, l = 3, 82
+//line foo/bar.y:90
+	f, l = 3, 90
+//line foo/bar.y:92
+	f, l = 3, 92
+//line foo/bar.y:100
+	f, l = 3, 100
+//line foo/bar.y:104
+	l = 104
+//line foo/bar.y:112
+	l = 112
+//line foo/bar.y:117
+	l = 117
+//line foo/bar.y:121
+	l = 121
+//line foo/bar.y:125
+	l = 125
+//line foo/bar.y:133
+	l = 133
+//line foo/bar.y:146
+	l = 146
+//line foo/bar.y:148
+//line foo/bar.y:153
+//line foo/bar.y:155
+	l = 155
+//line foo/bar.y:160
+
+//line foo/bar.y:164
+//line foo/bar.y:173
+
+//line foo/bar.y:178
+//line foo/bar.y:180
+//line foo/bar.y:185
+//line foo/bar.y:195
+//line foo/bar.y:197
+//line foo/bar.y:202
+//line foo/bar.y:204
+//line foo/bar.y:208
+//line foo/bar.y:211
+//line foo/bar.y:213
+//line foo/bar.y:215
+//line foo/bar.y:217
+//line foo/bar.y:221
+//line foo/bar.y:229
+//line foo/bar.y:236
+//line foo/bar.y:238
+//line foo/bar.y:240
+//line foo/bar.y:244
+//line foo/bar.y:249
+//line foo/bar.y:253
+//line foo/bar.y:257
+//line foo/bar.y:262
+//line foo/bar.y:267
+//line foo/bar.y:272
+	if l == f {
+//line foo/bar.y:277
+	panic("aie!")
+//line foo/bar.y:281
+	}
+//line foo/bar.y:285
+	return
+//line foo/bar.y:288
+//line foo/bar.y:290
+}
+//line foo/bar.y:293
+//line foo/bar.y:295

test/dwarf/main.go

+// $G $D/$F.go $D/z*.go && $L $F.$A && ./$A.out
+
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+func main() {
+F1()
+F2()
+F3()
+F4()
+F5()
+F6()
+F7()
+F8()
+F9()
+F10()
+F11()
+F12()
+F13()
+F14()
+F15()
+F16()
+F17()
+F18()
+F19()
+F20()
+}

test/dwarf/z1.go

+
+
+//line x1.go:4
+package main
+func F1() {}

test/dwarf/z10.go

+
+
+
+//line x10.go:4
+package main
+func F10() {}

test/dwarf/z11.go

+
+//line x11.go:4
+package main
+func F11() {}

test/dwarf/z12.go

+
+//line x12.go:4
+package main
+func F12() {}

test/dwarf/z13.go

+
+//line x13.go:4
+package main
+func F13() {}

test/dwarf/z14.go

+
+//line x14.go:4
+package main
+func F14() {}

test/dwarf/z15.go

+
+//line x15.go:4
+package main
+func F15() {}

test/dwarf/z16.go

+
+//line x16.go:4
+package main
+func F16() {}

test/dwarf/z17.go

+
+//line x17.go:4
+package main
+func F17() {}

test/dwarf/z18.go

+
+
+//line x18.go:4
+package main
+func F18() {}

test/dwarf/z19.go

+
+//line x19.go:4
+package main
+func F19() {}

test/dwarf/z2.go

+
+//line x2.go:4
+package main
+func F2() {}

test/dwarf/z20.go

+
+//line x20.go:4
+package main
+func F20() {}

test/dwarf/z3.go

+
+//line x3.go:4
+package main
+func F3() {}

test/dwarf/z4.go

+
+//line x4.go:4
+package main
+func F4() {}

test/dwarf/z5.go

+
+//line x5.go:4
+package main
+func F5() {}

test/dwarf/z6.go

+
+//line x6.go:4
+package main
+func F6() {}

test/dwarf/z7.go

+
+//line x7.go:4
+package main
+func F7() {}

test/dwarf/z8.go

+
+//line x8.go:4
+package main
+func F8() {}

test/dwarf/z9.go

+
+//line x9.go:4
+package main
+func F9() {}

test/golden.out

@@ -115,6 +115,8 @@ panic: interface conversion: *main.S is not main.I2: missing method Name
 
 == syntax/
 
+== dwarf/
+
 == fixedbugs/
 
 =========== fixedbugs/bug027.go

test/run

@@ -53,7 +53,7 @@ filterout() {
 	grep '^'"$2"'$' $1 >/dev/null
 }
 
-for dir in . ken chan interface nilptr syntax fixedbugs bugs
+for dir in . ken chan interface nilptr syntax dwarf fixedbugs bugs
 do
 	echo
 	echo '==' $dir'/'