cov: clean up pvid and vgid usage

pvid and vgid are sometimes a null-terminated string, and
other times a 'struct id', and the two types were often
cast between each other.  When a struct id was cast to a char
pointer, the resulting string would not necessarily be null
terminated.  Casting a null-terminated string id to a
struct id is fine, but is still avoided when possible.

A struct id is:  int8_t uuid[ID_LEN]
A string id is:  char pvid[ID_LEN + 1]

A convention is introduced to help distinguish them:

- variables and struct fields named "pvid" or "vgid"
  should be null-terminated strings.

- variables and struct fields named "pv_id" or "vg_id"
  should be struct id's.

- examples:
  char pvid[ID_LEN + 1];
  char vgid[ID_LEN + 1];
  struct id pv_id;
  struct id vg_id;

Function names also attempt to follow this convention.

Avoid casting between the two types as much as possible,
with limited exceptions when known to be safe and clearly
commented.

Avoid using variations of strcpy and strcmp, and instead
use memcpy/memcmp with ID_LEN (with similar limited
exceptions possible.)

1 files changed, 1 insertions, 1 deletions

diff --git a/lib/activate/dev_manager.c b/lib/activate/dev_manager.c
index c4a673901..2ada9b525 100644
--- a/lib/activate/dev_manager.c
+++ b/lib/activate/dev_manager.c
@@ -2118,7 +2118,7 @@ static int _check_holder(struct dev_manager *dm, struct dm_tree *dtree,
 		if (!strncmp(default_uuid_prefix, uuid, default_uuid_prefix_len))
 			uuid += default_uuid_prefix_len;
 
-		if (!strncmp(uuid, (char*)&lv->vg->id, sizeof(lv->vg->id)) &&
+		if (!memcmp(uuid, &lv->vg->id, ID_LEN) &&
 		    !dm_tree_find_node_by_uuid(dtree, uuid)) {
 			/* trims any UUID suffix (i.e. -cow) */
 			(void) dm_strncpy((char*)&id, uuid, 2 * sizeof(struct id) + 1);