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[PATCH] show-branch: convert object.flags usage to a commit-slab

From
GRGatla Vishweshwar Reddy <gatlavishweshwarreddy26@gmail.com>
Date
Jul 14, 2026, 18:30 UTC
Message-ID
<20260714183028.67857-1-gatlavishweshwarreddy26@gmail.com>

show-branch uses commit->object.flags to store two kinds of per-commit data: the UNINTERESTING bit to mark commits that are ancestors of all given revisions, and per-branch reachability bits (one bit per branch, starting at REV_SHIFT) to track which branches can reach each commit.

Using the shared object.flags field for this purpose is fragile. The field is shared across the entire Git codebase and other subsystems use it for their own bookkeeping. Storing show-branch specific data there risks conflicts with other users of the same field.

Convert this usage to a dedicated commit-slab named commit_rev_flags, which is the canonical way to associate per-commit data in Git without polluting the shared object flags. Add helper functions get_rev_flags() and or_rev_flags() to encapsulate slab access cleanly, and initialize and clear the slab in cmd_show_branch() to avoid memory leaks.

Signed-off-by: Gatla Vishweshwar Reddy <gatlavishweshwarreddy26@gmail.com>
---
 builtin/show-branch.c | 62 +++++++++++++++++++++++++++----------------
 1 file changed, 39 insertions(+), 23 deletions(-)
diff --git a/builtin/show-branch.c b/builtin/show-branch.c
index f02831b085..ad3a85fafa 100644
--- a/builtin/show-branch.c
+++ b/builtin/show-branch.c
@@ -34,13 +34,11 @@ static enum git_colorbool showbranch_use_color = GIT_COLOR_UNKNOWN;
 
 static struct strvec default_args = STRVEC_INIT;
 
-/*
- * TODO: convert this use of commit->object.flags to commit-slab
- * instead to store a pointer to ref name directly. Then use the same
- * UNINTERESTING definition from revision.h here.
- */
 #define UNINTERESTING	01
 
+static unsigned int get_rev_flags(struct commit *commit);
+static void or_rev_flags(struct commit *commit, unsigned int flags);
+
 #define REV_SHIFT	 2
 #define MAX_REVS	(FLAG_BITS - REV_SHIFT) /* should not exceed bits_per_int - REV_SHIFT */
 
@@ -64,7 +62,7 @@ static struct commit *interesting(struct prio_queue *queue)
 {
 	for (size_t i = 0; i < queue->nr; i++) {
 		struct commit *commit = queue->array[i].data;
-		if (commit->object.flags & UNINTERESTING)
+		if (get_rev_flags(commit) & UNINTERESTING)
 			continue;
 		return commit;
 	}
@@ -79,11 +77,25 @@ struct commit_name {
 define_commit_slab(commit_name_slab, struct commit_name *);
 static struct commit_name_slab name_slab;
 
+define_commit_slab(commit_rev_flags, unsigned int);
+static struct commit_rev_flags rev_flags_slab;
+
 static struct commit_name *commit_to_name(struct commit *commit)
 {
 	return *commit_name_slab_at(&name_slab, commit);
 }
 
+static unsigned int get_rev_flags(struct commit *commit)
+{
+	unsigned int *f = commit_rev_flags_peek(&rev_flags_slab, commit);
+	return f ? *f : 0;
+}
+
+static void or_rev_flags(struct commit *commit, unsigned int flags)
+{
+	*commit_rev_flags_at(&rev_flags_slab, commit) |= flags;
+}
+
 
 /* Name the commit as nth generation ancestor of head_name;
  * we count only the first-parent relationship for naming purposes.
@@ -215,7 +227,7 @@ static void name_commits(struct commit_list *list,
 
 static int mark_seen(struct commit *commit, struct commit_list **seen_p)
 {
-	if (!commit->object.flags) {
+	if (!get_rev_flags(commit)) {
 		commit_list_insert(commit, seen_p);
 		return 1;
 	}
@@ -234,7 +246,7 @@ static void join_revs(struct prio_queue *queue,
 		int still_interesting = !!interesting(queue);
 		struct commit *commit = prio_queue_peek(queue);
 		bool get_pending = true;
-		int flags = commit->object.flags & all_mask;
+		int flags = get_rev_flags(commit) & all_mask;
 
 		if (!still_interesting && extra <= 0)
 			break;
@@ -246,14 +258,14 @@ static void join_revs(struct prio_queue *queue,
 
 		while (parents) {
 			struct commit *p = parents->item;
-			int this_flag = p->object.flags;
+			int this_flag = get_rev_flags(p);
 			parents = parents->next;
 			if ((this_flag & flags) == flags)
 				continue;
 			repo_parse_commit(the_repository, p);
 			if (mark_seen(p, seen_p) && !still_interesting)
 				extra--;
-			p->object.flags |= flags;
+			or_rev_flags(p, flags);
 			if (get_pending)
 				prio_queue_replace(queue, p);
 			else
@@ -278,8 +290,8 @@ static void join_revs(struct prio_queue *queue,
 			struct commit *c = s->item;
 			struct commit_list *parents;
 
-			if (((c->object.flags & all_revs) != all_revs) &&
-			    !(c->object.flags & UNINTERESTING))
+			if (((get_rev_flags(c) & all_revs) != all_revs) &&
+			    !(get_rev_flags(c) & UNINTERESTING))
 				continue;
 
 			/* The current commit is either a merge base or
@@ -292,8 +304,8 @@ static void join_revs(struct prio_queue *queue,
 			while (parents) {
 				struct commit *p = parents->item;
 				parents = parents->next;
-				if (!(p->object.flags & UNINTERESTING)) {
-					p->object.flags |= UNINTERESTING;
+				if (!(get_rev_flags(p) & UNINTERESTING)) {
+					or_rev_flags(p, UNINTERESTING);
 					changed = 1;
 				}
 			}
@@ -517,12 +529,14 @@ static int show_merge_base(const struct commit_list *seen, int num_rev)
 
 	for (const struct commit_list *s = seen; s; s = s->next) {
 		struct commit *commit = s->item;
-		int flags = commit->object.flags & all_mask;
+		int flags = get_rev_flags(commit) & all_mask;
 		if (!(flags & UNINTERESTING) &&
 		    ((flags & all_revs) == all_revs)) {
 			puts(oid_to_hex(&commit->object.oid));
 			exit_status = 0;
-			commit->object.flags |= UNINTERESTING;
+
+or_rev_flags(commit, UNINTERESTING);
+
 		}
 	}
 	return exit_status;
@@ -538,9 +552,9 @@ static int show_independent(struct commit **rev,
 		struct commit *commit = rev[i];
 		unsigned int flag = rev_mask[i];
 
-		if (commit->object.flags == flag)
+		if (get_rev_flags(commit) == flag)
 			puts(oid_to_hex(&commit->object.oid));
-		commit->object.flags |= UNINTERESTING;
+		or_rev_flags(commit, UNINTERESTING);
 	}
 	return 0;
 }
@@ -607,7 +621,7 @@ static int omit_in_dense(struct commit *commit, struct commit **rev, int n)
 	for (i = 0; i < n; i++)
 		if (rev[i] == commit)
 			return 0;
-	flag = commit->object.flags;
+	flag = get_rev_flags(commit);
 	for (i = count = 0; i < n; i++) {
 		if (flag & (1u << (i + REV_SHIFT)))
 			count++;
@@ -714,6 +728,7 @@ int cmd_show_branch(int ac,
 	int ret;
 
 	init_commit_name_slab(&name_slab);
+	init_commit_rev_flags(&rev_flags_slab);
 
 	repo_config(the_repository, git_show_branch_config, NULL);
 
@@ -889,13 +904,13 @@ int cmd_show_branch(int ac,
 		 * and so on.  REV_SHIFT bits from bit 0 are used for
 		 * internal bookkeeping.
 		 */
-		commit->object.flags |= flag;
-		if (commit->object.flags == flag)
+		or_rev_flags(commit, flag);
+		if (get_rev_flags(commit) == flag)
 			prio_queue_put(&queue, commit);
 		rev[num_rev] = commit;
 	}
 	for (i = 0; i < num_rev; i++)
-		rev_mask[i] = rev[i]->object.flags;
+		rev_mask[i] = get_rev_flags(rev[i]);
 
 	if (0 <= extra)
 		join_revs(&queue, &seen, num_rev, extra);
@@ -963,7 +978,7 @@ int cmd_show_branch(int ac,
 
 	for (struct commit_list *l = seen; l; l = l->next) {
 		struct commit *commit = l->item;
-		int this_flag = commit->object.flags;
+		int this_flag = get_rev_flags(commit);
 		int is_merge_point = ((this_flag & all_revs) == all_revs);
 
 		shown_merge_point |= is_merge_point;
@@ -1010,6 +1025,7 @@ int cmd_show_branch(int ac,
 		free(reflog_msg[i]);
 	commit_list_free(seen);
 	clear_prio_queue(&queue);
+	clear_commit_rev_flags(&rev_flags_slab);
 	free(args_copy);
 	free(head);
 	return ret;

-- 
2.54.0
Next: Gatla Vishweshwar Reddy
Message 1 of 27 in “show-branch: convert object.flags usage to a commit-slab”
  1. show-branch: convert object.flags usage to a commit-slabGatla Vishweshwar Reddy, Jul 14, 2026
  2. show-branch: convert object.flags to commit-slab with uint64_tGatla Vishweshwar Reddy, Jul 14, 2026
  3. Junio C HamanoJul 14, 2026
  4. Jeff KingJul 14, 2026
  5. show-branch: convert per-branch flags to commit-slabGatla Vishweshwar Reddy, Jul 15, 2026
  6. Junio C HamanoJul 15, 2026
  7. show-branch: convert per-branch flags to commit-slabGatla Vishweshwar Reddy, Jul 15, 2026
  8. Patrick SteinhardtJul 15, 2026
  9. Junio C HamanoJul 15, 2026
  10. show-branch: convert per-branch flags to commit-slabGatla Vishweshwar Reddy, Jul 15, 2026
  11. Junio C HamanoJul 15, 2026
  12. show-branch: convert per-branch flags to commit-slabGatla Vishweshwar Reddy, Jul 15, 2026
  13. Junio C HamanoJul 17, 2026
  14. show-branch: convert per-branch flags to commit-slabGatla Vishweshwar Reddy, Jul 17, 2026
  15. Patrick SteinhardtJul 17, 2026
  16. Gatla Vishweshwar ReddyJul 17, 2026
  17. Patrick SteinhardtJul 17, 2026
  18. Junio C HamanoJul 17, 2026
  19. show-branch: convert per-branch flags to commit-slabGatla Vishweshwar Reddy, Jul 17, 2026
  20. Junio C HamanoJul 17, 2026
  21. show-branch: convert per-branch flags to commit-slabGatla Vishweshwar Reddy, Jul 17, 2026
  22. Junio C HamanoJul 21, 2026
  23. show-branch: convert per-branch flags to commit-slabGatla Vishweshwar Reddy, Jul 21, 2026
  24. Junio C HamanoJul 23, 2026
  25. Gatla Vishweshwar ReddyJul 23, 2026
  26. Gatla Vishweshwar ReddyJul 24, 2026
  27. Patrick SteinhardtJul 17, 2026

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