@matheusbsbs / matheus-bagliano / commits / 31faeb2088

object_array_entry: fix memory handling of the name field

Previously, the memory management of the object_array_entry::name field was inconsistent and undocumented. object_array_entries are ultimately created by a single function, add_object_array_with_mode(), which has an argument "const char *name". This function used to simply set the name field to reference the string pointed to by the name parameter, and nobody on the object_array side ever freed the memory. Thus, it assumed that the memory for the name field would be managed by the caller, and that the lifetime of that string would be at least as long as the lifetime of the object_array_entry. But callers were inconsistent: * Some passed pointers to constant strings or argv entries, which was OK. * Some passed pointers to newly-allocated memory, but didn't arrange for the memory ever to be freed. * Some passed the return value of sha1_to_hex(), which is a pointer to a statically-allocated buffer that can be overwritten at any time. * Some passed pointers to refnames that they received from a for_each_ref()-type iteration, but the lifetimes of such refnames is not guaranteed by the refs API. Bring consistency to this mess by changing object_array to make its own copy for the object_array_entry::name field and free this memory when an object_array_entry is deleted from the array. Many callers were passing the empty string as the name parameter, so as a performance optimization, treat the empty string specially. Instead of making a copy, store a pointer to a statically-allocated empty string to object_array_entry::name. When deleting such an entry, skip the free(). Change the callers that were already passing copies to add_object_array_with_mode() to either skip the copy, or (if the memory needed to be allocated anyway) freeing the memory itself. A part of this commit effectively reverts 70d26c6e76 read_revisions_from_stdin: make copies for handle_revision_arg because the copying introduced by that commit (which is still necessary) is now done at a deeper level. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Michael Haggerty committed May 25, 2013 at 11:08 UTC 31faeb2088ef35d0108ad81df3550513d6cec798

4 files changed +35 -7

bundle.c

+1 -1

@@ -281,7 +281,7 @@ int create_bundle(struct bundle_header *header, const char *path,

281 if (!get_sha1_hex(buf.buf + 1, sha1)) {

282 struct object *object = parse_object_or_die(sha1, buf.buf);

283 object->flags |= UNINTERESTING;

284 - add_pending_object(&revs, object, xstrdup(buf.buf));

284 + add_pending_object(&revs, object, buf.buf);

285 }

286 } else if (!get_sha1_hex(buf.buf, sha1)) {

287 struct object *object = parse_object_or_die(sha1, buf.buf);

object.c

+23 -3

@@ -260,11 +260,18 @@ void add_object_array(struct object *obj, const char *name, struct object_array

260 add_object_array_with_mode(obj, name, array, S_IFINVALID);

261 }

262

263 +/*

264 + * A zero-length string to which object_array_entry::name can be

265 + * initialized without requiring a malloc/free.

266 + */

267 +static char object_array_slopbuf[1];

268 +

269 void add_object_array_with_mode(struct object *obj, const char *name, struct object_array *array, unsigned mode)

270 {

271 unsigned nr = array->nr;

272 unsigned alloc = array->alloc;

273 struct object_array_entry *objects = array->objects;

274 + struct object_array_entry *entry;

275

276 if (nr >= alloc) {

277 alloc = (alloc + 32) * 2;

@@ -272,9 +279,16 @@ void add_object_array_with_mode(struct object *obj, const char *name, struct obj

279 array->alloc = alloc;

280 array->objects = objects;

281 }

275 - objects[nr].item = obj;

276 - objects[nr].name = name;

277 - objects[nr].mode = mode;

282 + entry = &objects[nr];

283 + entry->item = obj;

284 + if (!name)

285 + entry->name = NULL;

286 + else if (!*name)

287 + /* Use our own empty string instead of allocating one: */

288 + entry->name = object_array_slopbuf;

289 + else

290 + entry->name = xstrdup(name);

291 + entry->mode = mode;

292 array->nr = ++nr;

293 }

294

@@ -289,6 +303,9 @@ void object_array_filter(struct object_array *array,

303 if (src != dst)

304 objects[dst] = objects[src];

305 dst++;

306 + } else {

307 + if (objects[src].name != object_array_slopbuf)

308 + free(objects[src].name);

309 }

310 }

311 array->nr = dst;

@@ -319,6 +336,9 @@ void object_array_remove_duplicates(struct object_array *array)

336 if (src != array->nr)

337 objects[array->nr] = objects[src];

338 array->nr++;

339 + } else {

340 + if (objects[src].name != object_array_slopbuf)

341 + free(objects[src].name);

342 }

343 }

344 }

object.h

+7 -1

@@ -11,7 +11,13 @@ struct object_array {

11 unsigned int alloc;

12 struct object_array_entry {

13 struct object *item;

14 - const char *name;

14 + /*

15 + * name or NULL. If non-NULL, the memory pointed to

16 + * is owned by this object *except* if it points at

17 + * object_array_slopbuf, which is a static copy of the

18 + * empty string.

19 + */

20 + char *name;

21 unsigned mode;

22 } *objects;

23 };

revision.c

+4 -2

@@ -88,7 +88,9 @@ void add_object(struct object *obj,

88 struct name_path *path,

89 const char *name)

90 {

91 - add_object_array(obj, path_name(path, name), p);

91 + char *pn = path_name(path, name);

92 + add_object_array(obj, pn, p);

93 + free(pn);

94 }

96 static void mark_blob_uninteresting(struct blob *blob)

@@ -1288,7 +1290,7 @@ static void read_revisions_from_stdin(struct rev_info *revs,

1290 }

1291 die("options not supported in --stdin mode");

1292 }

1291 - if (handle_revision_arg(xstrdup(sb.buf), revs, 0,

1293 + if (handle_revision_arg(sb.buf, revs, 0,

1294 REVARG_CANNOT_BE_FILENAME))

1295 die("bad revision '%s'", sb.buf);

1296 }