real_path: remove unsafe API

Returning a shared buffer invites very subtle bugs due to reentrancy or
multi-threading, as demonstrated by the previous patch.

There was an unfinished effort to abolish this [1].

Let's finally rid of `real_path()`, using `strbuf_realpath()` instead.

This patch uses a local `strbuf` for most places where `real_path()` was
previously called.

However, two places return the value of `real_path()` to the caller. For
them, a `static` local `strbuf` was added, effectively pushing the
problem one level higher:
    read_gitfile_gently()
    get_superproject_working_tree()

[1] https://lore.kernel.org/git/1480964316-99305-1-git-send-email-bmwill@google.com/

Signed-off-by: Alexandr Miloslavskiy <alexandr.miloslavskiy@syntevo.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Alexandr Miloslavskiy
2020-03-10 13:11:22 +00:00
committed by Junio C Hamano
parent 0915a5b4cd
commit 3d7747e318
13 changed files with 59 additions and 24 deletions

View File

@ -39,14 +39,17 @@ static struct object_directory *find_odb(struct repository *r,
{
struct object_directory *odb;
char *obj_dir_real = real_pathdup(obj_dir, 1);
struct strbuf odb_path_real = STRBUF_INIT;
prepare_alt_odb(r);
for (odb = r->objects->odb; odb; odb = odb->next) {
if (!strcmp(obj_dir_real, real_path(odb->path)))
strbuf_realpath(&odb_path_real, odb->path, 1);
if (!strcmp(obj_dir_real, odb_path_real.buf))
break;
}
free(obj_dir_real);
strbuf_release(&odb_path_real);
if (!odb)
die(_("could not find object directory matching %s"), obj_dir);