From: Ethan Glasser-Camp Date: Sun, 21 Oct 2012 01:46:39 +0000 (+2000) Subject: Re: [PATCH] lib: fix warnings when building with clang X-Git-Url: http://git.tremily.us/gitweb.cgi?a=commitdiff_plain;h=4836bc5cce6cb3dd83e068c54e395ee82b98b62a;p=notmuch-archives.git Re: [PATCH] lib: fix warnings when building with clang --- diff --git a/66/94d36309a79bfce9bb86802d5e28bbcc487c8d b/66/94d36309a79bfce9bb86802d5e28bbcc487c8d new file mode 100644 index 000000000..cd08f277c --- /dev/null +++ b/66/94d36309a79bfce9bb86802d5e28bbcc487c8d @@ -0,0 +1,132 @@ +Return-Path: +X-Original-To: notmuch@notmuchmail.org +Delivered-To: notmuch@notmuchmail.org +Received: from localhost (localhost [127.0.0.1]) + by olra.theworths.org (Postfix) with ESMTP id 543AE431FAF + for ; Sat, 20 Oct 2012 18:46:45 -0700 (PDT) +X-Virus-Scanned: Debian amavisd-new at olra.theworths.org +X-Spam-Flag: NO +X-Spam-Score: -0.799 +X-Spam-Level: +X-Spam-Status: No, score=-0.799 tagged_above=-999 required=5 + tests=[DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, + FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_LOW=-0.7] autolearn=disabled +Received: from olra.theworths.org ([127.0.0.1]) + by localhost (olra.theworths.org [127.0.0.1]) (amavisd-new, port 10024) + with ESMTP id XDU51ezOWXJZ for ; + Sat, 20 Oct 2012 18:46:44 -0700 (PDT) +Received: from mail-vc0-f181.google.com (mail-vc0-f181.google.com + [209.85.220.181]) (using TLSv1 with cipher RC4-SHA (128/128 bits)) + (No client certificate requested) + by olra.theworths.org (Postfix) with ESMTPS id 9405C431FAE + for ; Sat, 20 Oct 2012 18:46:44 -0700 (PDT) +Received: by mail-vc0-f181.google.com with SMTP id n11so1909718vch.26 + for ; Sat, 20 Oct 2012 18:46:42 -0700 (PDT) +DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; + h=from:to:subject:in-reply-to:references:user-agent:date:message-id + :mime-version:content-type; + bh=im1CbZ8uFOgVenJY3mO7AtoSAq28Pgp+cjOV+l2zAhQ=; + b=nVNIiHE8ZLfgVINsPs1Ggnpjv4llZQv/2HLzjbZ1ziUnlolEt4ZCHHbgjtMY+Y0aFE + 0inYfK0YITIaUnteBL7iUmwxeDnx+g+p48BFzXliG78+ZDbl29oSNv8k/eRLMppPIuLH + YMUdo3j8eXdSpWKf2P9xHWSWQ4sF1FPpiN9vXx54pcJbdbvAvFuv25LyTmfD7B+IOwY5 + 2ui8wRysOVk9jME+DZ7/TFtJ8sBlvCtw2HgAK/LIOaF4ilIlSMHQQNwM5Ru8Iif79teD + Ra2C/0U+4e85eArjNcepwMiBiMTVcjgbqlX8vXG591qiUcIZOU4g6syLHpX4/CfgWvm3 + NWrg== +Received: by 10.220.220.5 with SMTP id hw5mr8024596vcb.53.1350784002732; + Sat, 20 Oct 2012 18:46:42 -0700 (PDT) +Received: from smtp.gmail.com (p70-80.acedsl.com. [66.114.70.80]) + by mx.google.com with ESMTPS id y15sm6004289vdt.9.2012.10.20.18.46.40 + (version=TLSv1/SSLv3 cipher=OTHER); + Sat, 20 Oct 2012 18:46:41 -0700 (PDT) +From: Ethan Glasser-Camp +To: Jani Nikula , notmuch@notmuchmail.org +Subject: Re: [PATCH] lib: fix warnings when building with clang +In-Reply-To: <1349076971-2065-1-git-send-email-jani@nikula.org> +References: <1349076971-2065-1-git-send-email-jani@nikula.org> +User-Agent: Notmuch/0.14+45~g6ea9330 (http://notmuchmail.org) Emacs/23.3.1 + (x86_64-pc-linux-gnu) +Date: Sat, 20 Oct 2012 21:46:39 -0400 +Message-ID: <87pq4c61hc.fsf@betacantrips.com> +MIME-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +X-BeenThere: notmuch@notmuchmail.org +X-Mailman-Version: 2.1.13 +Precedence: list +List-Id: "Use and development of the notmuch mail system." + +List-Unsubscribe: , + +List-Archive: +List-Post: +List-Help: +List-Subscribe: , + +X-List-Received-Date: Sun, 21 Oct 2012 01:46:45 -0000 + +Jani Nikula writes: + +> Building notmuch with CC=clang and CXX=clang++ produces the warnings: +> +> CC -O2 lib/tags.o +> lib/tags.c:43:5: warning: expression result unused [-Wunused-value] +> talloc_steal (tags, list); +> ^~~~~~~~~~~~~~~~~~~~~~~~~ +> /usr/include/talloc.h:345:143: note: expanded from: +> ...__location__); __talloc_steal_ret; }) +> ^~~~~~~~~~~~~~~~~~ +> 1 warning generated. +> +> CXX -O2 lib/message.o +> lib/message.cc:791:5: warning: expression result unused [-Wunused-value] +> talloc_reference (message, message->tag_list); +> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +> /usr/include/talloc.h:932:36: note: expanded from: +> ...(_TALLOC_TYPEOF(ptr))_talloc_reference_loc((ctx),(ptr), __location__) +> ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +> 1 warning generated. +> +> Check talloc_reference() return value, and explicitly ignore +> talloc_steal() return value as it has no failure modes, to silence the +> warnings. +> --- +> lib/message.cc | 4 +++- +> lib/tags.c | 2 +- +> 2 files changed, 4 insertions(+), 2 deletions(-) +> +> diff --git a/lib/message.cc b/lib/message.cc +> index 978de06..320901f 100644 +> --- a/lib/message.cc +> +++ b/lib/message.cc +> @@ -788,7 +788,9 @@ notmuch_message_get_tags (notmuch_message_t *message) +> * possible to modify the message tags (which talloc_unlink's the +> * current list from the message) while still iterating because +> * the iterator will keep the current list alive. */ +> - talloc_reference (message, message->tag_list); +> + if (!talloc_reference (message, message->tag_list)) +> + return NULL; +> + +> return tags; +> } + +Hi! What you did with talloc_steal is obviously fine. + +I'd be happier about what you did with talloc_reference() if there were +precedent, or a clearly-articulated convention for notmuch. Instead this +is the third use in the codebase that I can see, and the other two are +each unique to themselves. In mime-node.c we print an "out-of-memory" +error and in lib/filenames.c we cast (void) talloc_reference (...), I +guess figuring that we're pretty much hosed anyhow if we run out of +memory. + +Why return NULL here? It seems like if talloc_reference fails, we're +going to crash eventually, so we should print an error to explain our +impending doom. I'd guess you're uneasy printing anything from lib/, but +still want to signal an error, and the only way you can do so is to +return NULL. I guess that silences the compiler warning, but it's not +really the correct way to handle the error IMO. On the other hand, it's +such a weird corner case that I don't even think it merits a FIXME +comment. + +How about an assert instead of a return NULL? + +Ethan