diff mbox series

[v4,04/13] attr: don't recompute default attribute source

Message ID 1204a342161235c38273981874add59031cb554e.1715057362.git.ps@pks.im (mailing list archive)
State New
Headers show
Series Stop relying on SHA1 fallback for `the_hash_algo` | expand

Commit Message

Patrick Steinhardt May 7, 2024, 4:53 a.m. UTC
The `default_attr_source()` function lazily computes the attr source
supposedly once, only. This is done via a static variable `attr_source`
that contains the resolved object ID of the attr source's tree. If the
variable is the null object ID then we try to look up the attr source,
otherwise we skip over it.

This approach is flawed though: the variable will never be set to
anything else but the null object ID in case there is no attr source.
Consequently, we re-compute the information on every call. And in the
worst case, when we silently ignore bad trees, this will cause us to try
and look up the treeish every single time.

Improve this by introducing a separate variable `has_attr_source` to
track whether we already computed the attr source and, if so, whether we
have an attr source or not.

This also allows us to convert the `ignore_bad_attr_tree` to not be
static anymore as the code will only be executed once anyway.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
---
 attr.c | 25 ++++++++++++++++---------
 1 file changed, 16 insertions(+), 9 deletions(-)
diff mbox series

Patch

diff --git a/attr.c b/attr.c
index 6af7151088..a5b717e4ce 100644
--- a/attr.c
+++ b/attr.c
@@ -1205,41 +1205,48 @@  static void collect_some_attrs(struct index_state *istate,
 	fill(path, pathlen, basename_offset, check->stack, check->all_attrs, rem);
 }
 
 static const char *default_attr_source_tree_object_name;
-static int ignore_bad_attr_tree;
 
 void set_git_attr_source(const char *tree_object_name)
 {
 	default_attr_source_tree_object_name = xstrdup(tree_object_name);
 }
 
-static void compute_default_attr_source(struct object_id *attr_source)
+static int compute_default_attr_source(struct object_id *attr_source)
 {
+	int ignore_bad_attr_tree = 0;
+
 	if (!default_attr_source_tree_object_name)
 		default_attr_source_tree_object_name = getenv(GIT_ATTR_SOURCE_ENVIRONMENT);
 
 	if (!default_attr_source_tree_object_name && git_attr_tree) {
 		default_attr_source_tree_object_name = git_attr_tree;
 		ignore_bad_attr_tree = 1;
 	}
 
-	if (!default_attr_source_tree_object_name || !is_null_oid(attr_source))
-		return;
+	if (!default_attr_source_tree_object_name)
+		return 0;
 
 	if (repo_get_oid_treeish(the_repository,
 				 default_attr_source_tree_object_name,
-				 attr_source) && !ignore_bad_attr_tree)
-		die(_("bad --attr-source or GIT_ATTR_SOURCE"));
+				 attr_source)) {
+		if (!ignore_bad_attr_tree)
+			die(_("bad --attr-source or GIT_ATTR_SOURCE"));
+		return 0;
+	}
+
+	return 1;
 }
 
 static struct object_id *default_attr_source(void)
 {
 	static struct object_id attr_source;
+	static int has_attr_source = -1;
 
-	if (is_null_oid(&attr_source))
-		compute_default_attr_source(&attr_source);
-	if (is_null_oid(&attr_source))
+	if (has_attr_source < 0)
+		has_attr_source = compute_default_attr_source(&attr_source);
+	if (!has_attr_source)
 		return NULL;
 	return &attr_source;
 }