Dive sites: don't delete unused dive sites on save

Unused dive sites were deleted on save. This clashed with the undo
system in the following scenario:

1) Delete single-use dive site.
2) Save (dive site deleted)
3) Undo (reference to freed dive site)

Therefore, as a quick-fix, keep the referenced dive site around.
Note that this also means that empty dive sites must not be
deleted, as it might refer to a dive in the undo system. Instead
only clear references to empty dive sites in the global dive
table. Factor this functionality out, as it was common to the
XML and git savers.

Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>

4 files changed, 24 insertions, 16 deletions

diff --git a/core/divesite.c b/core/divesite.c
index 726dec42d..d09597190 100644
--- a/core/divesite.c
+++ b/core/divesite.c
@@ -346,6 +346,23 @@ struct dive_site *find_or_create_dive_site_with_name(const char *name, timestamp
 	return create_dive_site(name, divetime);
 }
 
+void purge_empty_dive_sites()
+{
+	int i, j;
+	struct dive *d;
+	struct dive_site *ds;
+
+	for (i = 0; i < dive_site_table.nr; i++) {
+		ds = get_dive_site(i);
+		if (!dive_site_is_empty(ds))
+			continue;
+		for_each_dive(j, d) {
+			if (d->dive_site == ds)
+				d->dive_site = NULL;
+		}
+	}
+}
+
 static int compare_sites(const void *_a, const void *_b)
 {
 	const struct dive_site *a = (const struct dive_site *)*(void **)_a;
diff --git a/core/divesite.h b/core/divesite.h
index 3ce87128a..1cb0cbeff 100644
--- a/core/divesite.h
+++ b/core/divesite.h
@@ -73,6 +73,7 @@ void clear_dive_site(struct dive_site *ds);
 unsigned int get_distance(const location_t *loc1, const location_t *loc2);
 struct dive_site *find_or_create_dive_site_with_name(const char *name, timestamp_t divetime);
 void merge_dive_sites(struct dive_site *ref, struct dive_site *dive_sites[], int count);
+void purge_empty_dive_sites();
 
 #ifdef __cplusplus
 }
diff --git a/core/save-git.c b/core/save-git.c
index 7b903a5e9..cdc0ca980 100644
--- a/core/save-git.c
+++ b/core/save-git.c
@@ -879,18 +879,12 @@ static void save_divesites(git_repository *repo, struct dir *tree)
 	subdir = new_directory(repo, tree, &dirname);
 	free_buffer(&dirname);
 
+	purge_empty_dive_sites();
 	for (int i = 0; i < dive_site_table.nr; i++) {
 		struct membuffer b = { 0 };
 		struct dive_site *ds = get_dive_site(i);
-		if (dive_site_is_empty(ds) || !is_dive_site_used(ds, false)) {
-			int j;
-			struct dive *d;
-			for_each_dive(j, d) {
-				if (d->dive_site == ds)
-					d->dive_site = NULL;
-			}
-			delete_dive_site(ds);
-			i--; // since we just deleted that one
+		if (!is_dive_site_used(ds, false)) {
+			/* Only write used dive sites */
 			continue;
 		} else if (ds->name &&
 			   (strncmp(ds->name, "Auto-created dive", 17) == 0 ||
diff --git a/core/save-xml.c b/core/save-xml.c
index baebb0ad9..e49e186f4 100644
--- a/core/save-xml.c
+++ b/core/save-xml.c
@@ -592,18 +592,14 @@ void save_dives_buffer(struct membuffer *b, const bool select_only, bool anonymi
 
 	/* save the dive sites - to make the output consistent let's sort the table, first */
 	dive_site_table_sort();
+	purge_empty_dive_sites();
 	put_format(b, "<divesites>\n");
 	for (i = 0; i < dive_site_table.nr; i++) {
 		int j;
 		struct dive *d;
 		struct dive_site *ds = get_dive_site(i);
-		if (dive_site_is_empty(ds) || !is_dive_site_used(ds, false)) {
-			for_each_dive(j, d) {
-				if (d->dive_site == ds)
-					d->dive_site = NULL;
-			}
-			delete_dive_site(ds);
-			i--; // since we just deleted that one
+		if (!is_dive_site_used(ds, false)) {
+			/* Only write used dive sites */
 			continue;
 		} else if (ds->name &&
 			   (strncmp(ds->name, "Auto-created dive", 17) == 0 ||