[PATCH v4 02/27] refs.c: allow passing NULL to ref_transaction_free

From: Ronnie Sahlberg <sahlberg@google.com>
Date: Apr 28, 2014, 22:54 UTC
Message-ID: <1398725682-30782-3-git-send-email-sahlberg@google.com>
In-Reply-To: <1398725682-30782-1-git-send-email-sahlberg@google.com>

Allow ref_transaction_free to be called with NULL and in extension allow ref_transaction_rollback to be called for a NULL transaction.

This allows us to write code that will
  if ( (!transaction ||
        ref_transaction_update(...))  ||
      (ref_transaction_commit(...) && !(transaction = NULL)) {
          ref_transaction_rollback(transaction);
          ...
  }

In this case transaction is reset to NULL IFF ref_transaction_commit() was invoked and thus the rollback becomes ref_transaction_rollback(NULL) which is safe. IF the conditional triggered prior to ref_transaction_commit() then transaction is untouched and then ref_transaction_rollback(transaction) will rollback the failed transaction.

Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
---
 refs.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/refs.c b/refs.c
index 138ab70..2d83ef6 100644
--- a/refs.c
+++ b/refs.c
@@ -3303,6 +3303,9 @@ static void ref_transaction_free(struct ref_transaction *transaction)
 {
 	int i;
 
+	if (!transaction)
+		return;
+
 	for (i = 0; i < transaction->nr; i++)
 		free(transaction->updates[i]);

-- 
1.9.1.528.g98b8868.dirty