gopack: handle long lines in export data

Also, if the header is bad, exit with a non-zero status.

Other calls to Brdline in the tree, by category:

Reading symbol name from object file:
./cmd/5l/obj.c:486: 		name = Brdline(f, '\0');
./cmd/6l/obj.c:535: 		name = Brdline(f, '\0');
./cmd/8l/obj.c:564: 		name = Brdline(f, '\0');
./libmach/sym.c:292: 		cp = Brdline(bp, '\0');

Reading archive header line (fixed, short):
./cmd/gc/lex.c:287: 	if((a = Brdline(b, '\n')) == nil)
./cmd/gc/lex.c:303: 	if((p = Brdline(b, '\n')) == nil)

Reading object file header line (fixed, short):
./cmd/ld/lib.c:421: 	line = Brdline(f, '\n');

Reading undefined symbol list (unused code):
./cmd/ld/lib.c:773: 	while((l = Brdline(b, '\n')) != nil){

Implementing Brdstr:
./libbio/brdstr.c:36: 		p = Brdline(bp, delim);

The symbol names ones will cause a problem loudly if they
fail: they'll error out with symbol name too long.  This means
that you can't define an enormous struct without giving the
type a name and then stick it in an interface, because the
type's symbol name will be too long for the object file.
Since this will be a loud failure instead of a silent one,
I'm willing to wait until it comes up in practice.

R=r
CC=golang-dev
https://golang.org/cl/1982041

src/cmd/gopack/ar.c

@@ -601,17 +601,21 @@ scanobj(Biobuf *b, Arfile *ap, long size)
 	if (obj < 0) {			/* not an object file */
 		if (!gflag || strcmp(file, pkgdef) != 0) {  /* don't clear allobj if it's pkg defs */
 			fprint(2, "gopack: non-object file %s\n", file);
+			errors++;
 			allobj = 0;
 		}
 		d = dirfstat(Bfildes(b));
-		if (d != nil && d->length == 0)
+		if (d != nil && d->length == 0) {
 			fprint(2, "gopack: zero length file %s\n", file);
+			errors++;
+		}
 		free(d);
 		Bseek(b, offset, 0);
 		return;
 	}
 	if (lastobj >= 0 && obj != lastobj) {
 		fprint(2, "gopack: inconsistent object file %s\n", file);
+		errors++;
 		allobj = 0;
 		Bseek(b, offset, 0);
 		return;
@@ -619,6 +623,7 @@ scanobj(Biobuf *b, Arfile *ap, long size)
 	lastobj = obj;
 	if (!readar(b, obj, offset+size, 0)) {
 		fprint(2, "gopack: invalid symbol reference in file %s\n", file);
+		errors++;
 		allobj = 0;
 		Bseek(b, offset, 0);
 		return;
@@ -718,8 +723,8 @@ foundstart:
 	first = 1;
 	start = end = 0;
 	for (n=0; n<size; n+=Blinelen(b)) {
-		line = Brdline(b, '\n');
-		if (line == 0)
+		line = Brdstr(b, '\n', 0);
+		if (line == nil)
 			goto bad;
 		if (first && strstrn(line, Blinelen(b), "package ")) {
 			if (Blinelen(b) > sizeof(pkgbuf)-1)
@@ -742,14 +747,19 @@ foundstart:
 				safe = 0;
 			start = Boffset(b);  // after package statement
 			first = 0;
+			free(line);
 			continue;
 		}
-		if(line[0] == '$' && line[1] == '$')
+		if(line[0] == '$' && line[1] == '$') {
+			free(line);
 			goto foundend;
+		}
 		end = Boffset(b);  // before closing $$
+		free(line);
 	}
 bad:
 	fprint(2, "gopack: bad package import section in %s\n", file);
+	errors++;
 	return;
 
 foundend:
@@ -795,6 +805,7 @@ objsym(Sym *s, void *p)
 	if(s->type == 'T' && duplicate(as->name, &ofile)) {
 		dupfound = 1;
 		fprint(2, "duplicate text symbol: %s and %s: %s\n", as->file, ofile, as->name);
+		errors++;
 		free(as->name);
 		free(as);
 		return;

test/fixedbugs/bug302.dir/main.go

@@ -4,4 +4,9 @@
 
 package main
 
+// Check that the export information is correct in p.6.
 import _ "./p"
+
+// Check that it's still correct in pp.a (which contains p.6).
+import _ "./pp"
+

test/fixedbugs/bug302.go

@@ -1,4 +1,4 @@
-// $G $D/bug302.dir/p.go && $G $D/bug302.dir/main.go
+// $G $D/bug302.dir/p.go && gopack grc pp.a p.$A && $G $D/bug302.dir/main.go
 
 // Copyright 2010 The Go Authors.  All rights reserved.
 // Use of this source code is governed by a BSD-style

test/run

@@ -101,7 +101,7 @@ done | # clean up some stack noise
 		/Segmentation fault/d
 		/^qemu: uncaught target signal 11 (Segmentation fault) - exiting/d' > run.out
 
-rm  -f $RUNFILE $TMP1FILE $TMP2FILE *.$A $A.out
+rm  -f $RUNFILE $TMP1FILE $TMP2FILE *.$A *.a $A.out
 diffmsg=""
 if ! diff golden.out run.out
 then