From: Jani Nikula <jani@nikula.org>
To: David Bremner <david@tethera.net>, notmuch@notmuchmail.org
Subject: Re: [PATCH] lib: another iterator-temporary/stale-pointer bug
In-Reply-To: <1419763508-11902-1-git-send-email-david@tethera.net>
References: <20141226230655.GA41992@pamparam>
	<1419763508-11902-1-git-send-email-david@tethera.net>
User-Agent: Notmuch/0.19+3~g7585e8c (http://notmuchmail.org) Emacs/24.4.1
	(x86_64-pc-linux-gnu)
Date: Thu, 01 Jan 2015 16:49:31 +0200
Message-ID: <87wq56wo78.fsf@nikula.org>
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On Sun, 28 Dec 2014, David Bremner <david@tethera.net> wrote:
> Tamas Szakaly points out [1] that the bug fixed in 51b073c still
> exists in at least one place. This change follows the suggestion of
> [2] and creates a block scope temporary std::string to avoid the rules
> of iterators temporaries.
>
> [1]: id:20141226113755.GA64154@pamparam
> [2]: id:20141226230655.GA41992@pamparam
> ---
>
> I decided to take a more minimalist approach than [2]. In particular
> using "direntry" for two different things seemed slightly trickier
> than necessary, for no obvious performance gain (calling .c_str()
> should be cheap).
>
> lib/message.cc | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/lib/message.cc b/lib/message.cc
> index a7a13cc..bacb4d4 100644
> --- a/lib/message.cc
> +++ b/lib/message.cc
> @@ -641,15 +641,16 @@ _notmuch_message_add_directory_terms (void *ctx, notmuch_message_t *message)
>  	unsigned int directory_id;
>  	const char *direntry, *directory;
>  	char *colon;
> +	const std::string term = *i;

You could use a reference here like in [2]. Either way, LGTM.

Jani.

>  
>  	/* Terminate loop at first term without desired prefix. */
> -	if (strncmp ((*i).c_str (), direntry_prefix, direntry_prefix_len))
> +	if (strncmp (term.c_str (), direntry_prefix, direntry_prefix_len))
>  	    break;
>  
>  	/* Indicate that there are filenames remaining. */
>  	status = NOTMUCH_STATUS_DUPLICATE_MESSAGE_ID;
>  
> -	direntry = (*i).c_str ();
> +	direntry = term.c_str ();
>  	direntry += direntry_prefix_len;
>  
>  	directory_id = strtol (direntry, &colon, 10);
> -- 
> 2.1.3
>
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