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+ Sat, 20 Oct 2012 18:46:41 -0700 (PDT)\r
+From: Ethan Glasser-Camp <ethan.glasser.camp@gmail.com>\r
+To: Jani Nikula <jani@nikula.org>, notmuch@notmuchmail.org\r
+Subject: Re: [PATCH] lib: fix warnings when building with clang\r
+In-Reply-To: <1349076971-2065-1-git-send-email-jani@nikula.org>\r
+References: <1349076971-2065-1-git-send-email-jani@nikula.org>\r
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+Date: Sat, 20 Oct 2012 21:46:39 -0400\r
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+\r
+Jani Nikula <jani@nikula.org> writes:\r
+\r
+> Building notmuch with CC=clang and CXX=clang++ produces the warnings:\r
+>\r
+> CC -O2 lib/tags.o\r
+> lib/tags.c:43:5: warning: expression result unused [-Wunused-value]\r
+> talloc_steal (tags, list);\r
+> ^~~~~~~~~~~~~~~~~~~~~~~~~\r
+> /usr/include/talloc.h:345:143: note: expanded from:\r
+> ...__location__); __talloc_steal_ret; })\r
+> ^~~~~~~~~~~~~~~~~~\r
+> 1 warning generated.\r
+>\r
+> CXX -O2 lib/message.o\r
+> lib/message.cc:791:5: warning: expression result unused [-Wunused-value]\r
+> talloc_reference (message, message->tag_list);\r
+> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\r
+> /usr/include/talloc.h:932:36: note: expanded from:\r
+> ...(_TALLOC_TYPEOF(ptr))_talloc_reference_loc((ctx),(ptr), __location__)\r
+> ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\r
+> 1 warning generated.\r
+>\r
+> Check talloc_reference() return value, and explicitly ignore\r
+> talloc_steal() return value as it has no failure modes, to silence the\r
+> warnings.\r
+> ---\r
+> lib/message.cc | 4 +++-\r
+> lib/tags.c | 2 +-\r
+> 2 files changed, 4 insertions(+), 2 deletions(-)\r
+>\r
+> diff --git a/lib/message.cc b/lib/message.cc\r
+> index 978de06..320901f 100644\r
+> --- a/lib/message.cc\r
+> +++ b/lib/message.cc\r
+> @@ -788,7 +788,9 @@ notmuch_message_get_tags (notmuch_message_t *message)\r
+> * possible to modify the message tags (which talloc_unlink's the\r
+> * current list from the message) while still iterating because\r
+> * the iterator will keep the current list alive. */\r
+> - talloc_reference (message, message->tag_list);\r
+> + if (!talloc_reference (message, message->tag_list))\r
+> + return NULL;\r
+> +\r
+> return tags;\r
+> }\r
+\r
+Hi! What you did with talloc_steal is obviously fine. \r
+\r
+I'd be happier about what you did with talloc_reference() if there were\r
+precedent, or a clearly-articulated convention for notmuch. Instead this\r
+is the third use in the codebase that I can see, and the other two are\r
+each unique to themselves. In mime-node.c we print an "out-of-memory"\r
+error and in lib/filenames.c we cast (void) talloc_reference (...), I\r
+guess figuring that we're pretty much hosed anyhow if we run out of\r
+memory.\r
+\r
+Why return NULL here? It seems like if talloc_reference fails, we're\r
+going to crash eventually, so we should print an error to explain our\r
+impending doom. I'd guess you're uneasy printing anything from lib/, but\r
+still want to signal an error, and the only way you can do so is to\r
+return NULL. I guess that silences the compiler warning, but it's not\r
+really the correct way to handle the error IMO. On the other hand, it's\r
+such a weird corner case that I don't even think it merits a FIXME\r
+comment.\r
+\r
+How about an assert instead of a return NULL?\r
+\r
+Ethan\r
projects / notmuch-archives.git / commitdiff