Handle properly when insert zero size objects into the archive:

Do not mmap 0-size objects and do not try to extract symbol from
0-size objects, but do treat 0-size objects as qualified objects and
accept them as an archive member. (A member with only the header part)

Note that GNU binutils ar on FreeBSD ignores 0-size objects, but on
Linux it accepts them. [1] But, since this is a rare usage, we can
safely ignore the compatibility issue.

Reported by:	Michael Plass <mfp49_freebsd [AT] plass-family [DOT] net>
Pointed out by: Michael Plass <mfp49_freebsd [AT] plass-family [DOT] net> [1]
Reviewed by:	Michael Plass <mfp49_freebsd [AT] plass-family [DOT] net>
Reviewed by:	jkoshy
Approved by:	jkoshy (mentor)

1 files changed, 9 insertions, 3 deletions

diff --git a/usr.bin/ar/write.c b/usr.bin/ar/write.c
index 959fb68..2ead060 100644
--- a/usr.bin/ar/write.c
+++ b/usr.bin/ar/write.c
@@ -154,6 +154,12 @@ create_obj_from_file(struct bsdar *bsdar, const char *name, time_t mtime)
 	obj->mtime = sb.st_mtime;
 	obj->dev = sb.st_dev;
 	obj->ino = sb.st_ino;
+
+	if (obj->size == 0) {
+		obj->maddr = NULL;
+		return(obj);
+	}
+
 	if ((obj->maddr = mmap(NULL, obj->size, PROT_READ,
 	    MAP_PRIVATE, obj->fd, (off_t)0)) == MAP_FAILED) {
 		bsdar_warnc(bsdar, errno, "can't mmap file: %s", obj->name);
@@ -427,14 +433,14 @@ write_cleanup(struct bsdar *bsdar)
 	struct ar_obj		*obj, *obj_temp;
 
 	TAILQ_FOREACH_SAFE(obj, &bsdar->v_obj, objs, obj_temp) {
-		free(obj->name);
 		if (obj->fd == -1)
 			free(obj->maddr);
 		else
-			if (munmap(obj->maddr, obj->size))
+			if (obj->maddr != NULL && munmap(obj->maddr, obj->size))
 				bsdar_warnc(bsdar, errno,
 				    "can't munmap file: %s", obj->name);
 		TAILQ_REMOVE(&bsdar->v_obj, obj, objs);
+		free(obj->name);
 		free(obj);
 	}
 
@@ -478,7 +484,7 @@ write_objs(struct bsdar *bsdar)
 
 	/* Create archive symbol table and archive string table, if need. */
 	TAILQ_FOREACH(obj, &bsdar->v_obj, objs) {
-		if (!(bsdar->options & AR_SS))
+		if (!(bsdar->options & AR_SS) && obj->maddr != NULL)
 			create_symtab_entry(bsdar, obj->maddr, obj->size);
 		if (strlen(obj->name) > _MAXNAMELEN_SVR4)
 			add_to_ar_str_table(bsdar, obj->name);