Re: [PATCH 1/2] sequencer.c: check for lock failure and bail early in fast_forward_to

[Brandon Casey]

On Tue, Apr 15, 2014 at 4:46 PM, Ronnie Sahlberg  wrote:



> Signed-off-by: Ronnie Sahlberg 
> ---
>  sequencer.c | 7 +++
>  1 file changed, 7 insertions(+)
>
> diff --git a/sequencer.c b/sequencer.c
> index bde5f04..6aa3b50 100644
> --- a/sequencer.c
> +++ b/sequencer.c
> @@ -281,8 +281,15 @@ static int fast_forward_to(const unsigned char *to, 
> const unsigned char *from,
> exit(1); /* the callee should have complained already */
> ref_lock = lock_any_ref_for_update("HEAD", unborn ? null_sha1 : from,
>0, NULL);
> +   if (!ref_lock) {
> +   ret = error(_("Failed to lock HEAD during fast_forward_to"));
> +   goto leave;
> +   }
> +

Or just:

   if (!ref_lock)
   return error(_("Failed to lock HEAD ..."));

We don't need to strbuf_release() since the strbuf has not been
modified at this point.  We've only initialized with a static
initializer.

> strbuf_addf(&sb, "%s: fast-forward", action_name(opts));
> ret = write_ref_sha1(ref_lock, to, sb.buf);
> +
> +leave:
> strbuf_release(&sb);
> return ret;
>  }
> --

-Brandon
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[PATCH 1/2] sequencer.c: check for lock failure and bail early in fast_forward_to

[Ronnie Sahlberg]

Change fast_forward_to() to check if locking the ref failed, print a nice
error message and bail out early.
The old code did not check if ref_lock was NULL and relied on the fact
that the write_ref_sha1() would safely detect this condition and set the
return variable ret to indicate an error.
While that is safe, it makes the code harder to read for two reasons:
* Inconsistency.  Almost all other places we do check the lock for NULL
  explicitely, so the naive reader is confused "why don't we check here".
* And relying on write_ref_sha1() to detect and return an error for when
  a previous lock_any_ref_for_update() feels obfuscated.

This change should not change any functionality or logic
aside from adding an extra error message when this condition is triggered.
(write_ref_sha1() returns an error silently for this condition)

Signed-off-by: Ronnie Sahlberg 
---
 sequencer.c | 7 +++
 1 file changed, 7 insertions(+)

diff --git a/sequencer.c b/sequencer.c
index bde5f04..6aa3b50 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -281,8 +281,15 @@ static int fast_forward_to(const unsigned char *to, const 
unsigned char *from,
exit(1); /* the callee should have complained already */
ref_lock = lock_any_ref_for_update("HEAD", unborn ? null_sha1 : from,
   0, NULL);
+   if (!ref_lock) {
+   ret = error(_("Failed to lock HEAD during fast_forward_to"));
+   goto leave;
+   }
+
strbuf_addf(&sb, "%s: fast-forward", action_name(opts));
ret = write_ref_sha1(ref_lock, to, sb.buf);
+
+leave:
strbuf_release(&sb);
return ret;
 }
-- 
1.9.1.503.ge4c3920.dirty

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