[PATCH 3/7] find_unique_abbrev: use 4-buffer ring
- From
Jeff King <peff@peff.net>
- Date
- Oct 20, 2016, 06:19 UTC
- Message-ID
- <20161020061919.qu443ud7lbkopvth@sigill.intra.peff.net>
- In-Reply-To
- <20161020061536.6fqh23xb2nhxodpa@sigill.intra.peff.net>
Some code paths want to format multiple abbreviated sha1s in the same output line. Because we use a single static buffer for our return value, they have to either break their output into several calls or allocate their own arrays and use find_unique_abbrev_r().
Intead, let's mimic sha1_to_hex() and use a ring of several buffers, so that the return value stays valid through multiple calls. This shortens some of the callers, and makes it harder to for them to make a silly mistake.
Signed-off-by: Jeff King <peff@peff.net> --- It feels a little funny in these callers to be moving from a reentrant function to one that relies on a static buffer. But I feel like the result is more obvious and less error-prone, and the "ring of buffers" concept has proven useful and safe in sha1_to_hex().
My ulterior motive is that while refactoring one of the later patches, I just assumed that we did have a ring of buffers, and introduced a subtle bug.
builtin/merge.c | 11 +++++------ builtin/receive-pack.c | 16 ++++++---------- cache.h | 4 ++-- sha1_name.c | 4 +++- 4 files changed, 16 insertions(+), 19 deletions(-)
diff --git a/builtin/merge.c b/builtin/merge.c index a8b57c7..b65eeaa 100644 --- a/builtin/merge.c +++ b/builtin/merge.c @@ -1374,12 +1374,11 @@ int cmd_merge(int argc, const char **argv, const char *prefix) struct commit *commit; if (verbosity >= 0) { - char from[GIT_SHA1_HEXSZ + 1], to[GIT_SHA1_HEXSZ + 1]; - find_unique_abbrev_r(from, head_commit->object.oid.hash, - DEFAULT_ABBREV); - find_unique_abbrev_r(to, remoteheads->item->object.oid.hash, - DEFAULT_ABBREV); - printf(_("Updating %s..%s\n"), from, to); + printf(_("Updating %s..%s\n"), + find_unique_abbrev(head_commit->object.oid.hash, + DEFAULT_ABBREV), + find_unique_abbrev(remoteheads->item->object.oid.hash, + DEFAULT_ABBREV)); } strbuf_addstr(&msg, "Fast-forward"); if (have_message) diff --git a/builtin/receive-pack.c b/builtin/receive-pack.c index 04ed38e..680759d 100644 --- a/builtin/receive-pack.c +++ b/builtin/receive-pack.c @@ -1163,10 +1163,6 @@ static void check_aliased_update(struct command *cmd, struct string_list *list) struct string_list_item *item; struct command *dst_cmd; unsigned char sha1[GIT_SHA1_RAWSZ]; - char cmd_oldh[GIT_SHA1_HEXSZ + 1], - cmd_newh[GIT_SHA1_HEXSZ + 1], - dst_oldh[GIT_SHA1_HEXSZ + 1], - dst_newh[GIT_SHA1_HEXSZ + 1]; int flag; strbuf_addf(&buf, "%s%s", get_git_namespace(), cmd->ref_name); @@ -1197,14 +1193,14 @@ static void check_aliased_update(struct command *cmd, struct string_list *list) dst_cmd->skip_update = 1; - find_unique_abbrev_r(cmd_oldh, cmd->old_sha1, DEFAULT_ABBREV); - find_unique_abbrev_r(cmd_newh, cmd->new_sha1, DEFAULT_ABBREV); - find_unique_abbrev_r(dst_oldh, dst_cmd->old_sha1, DEFAULT_ABBREV); - find_unique_abbrev_r(dst_newh, dst_cmd->new_sha1, DEFAULT_ABBREV); rp_error("refusing inconsistent update between symref '%s' (%s..%s) and" " its target '%s' (%s..%s)", - cmd->ref_name, cmd_oldh, cmd_newh, - dst_cmd->ref_name, dst_oldh, dst_newh); + cmd->ref_name, + find_unique_abbrev(cmd->old_sha1, DEFAULT_ABBREV), + find_unique_abbrev(cmd->new_sha1, DEFAULT_ABBREV), + dst_cmd->ref_name, + find_unique_abbrev(dst_cmd->old_sha1, DEFAULT_ABBREV), + find_unique_abbrev(dst_cmd->new_sha1, DEFAULT_ABBREV)); cmd->error_string = dst_cmd->error_string = "inconsistent aliased update"; diff --git a/cache.h b/cache.h index 05ecb88..6e06311 100644 --- a/cache.h +++ b/cache.h @@ -901,8 +901,8 @@ extern char *sha1_pack_index_name(const unsigned char *sha1); * The result will be at least `len` characters long, and will be NUL * terminated. * - * The non-`_r` version returns a static buffer which will be overwritten by - * subsequent calls. + * The non-`_r` version returns a static buffer which remains valid until 4 + * more calls to find_unique_abbrev are made. * * The `_r` variant writes to a buffer supplied by the caller, which must be at * least `GIT_SHA1_HEXSZ + 1` bytes. The return value is the number of bytes diff --git a/sha1_name.c b/sha1_name.c index 4092836..36ce9b9 100644 --- a/sha1_name.c +++ b/sha1_name.c @@ -472,7 +472,9 @@ int find_unique_abbrev_r(char *hex, const unsigned char *sha1, int len) const char *find_unique_abbrev(const unsigned char *sha1, int len) { - static char hex[GIT_SHA1_HEXSZ + 1]; + static int bufno; + static char hexbuffer[4][GIT_SHA1_HEXSZ + 1]; + char *hex = hexbuffer[3 & ++bufno]; find_unique_abbrev_r(hex, sha1, len); return hex; }
-- 2.10.1.619.g16351a7