From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id C4091C36002 for ; Wed, 9 Apr 2025 10:09:49 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id A1D246B0175; Wed, 9 Apr 2025 06:09:48 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 9CC046B0176; Wed, 9 Apr 2025 06:09:48 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 846BC6B0177; Wed, 9 Apr 2025 06:09:48 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 62B4B6B0175 for ; Wed, 9 Apr 2025 06:09:48 -0400 (EDT) Received: from smtpin10.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id A679A1A0385 for ; Wed, 9 Apr 2025 10:09:48 +0000 (UTC) X-FDA: 83314084056.10.5E062D7 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf23.hostedemail.com (Postfix) with ESMTP id 0D624140008 for ; Wed, 9 Apr 2025 10:09:46 +0000 (UTC) Authentication-Results: imf23.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=arm.com; spf=pass (imf23.hostedemail.com: domain of anshuman.khandual@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=anshuman.khandual@arm.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1744193387; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=aOheeFgTCJ1OuR7HFu/5eCUY2i5I5YGs4Oe6AB+tCyg=; b=E/gGVG0w9CTkrBUiVJHEvmcqFhHzml4XQUIVqAP86u4JLLMrQM7IOYxMqBexa308hDudXE DFhd7/2nuRViZkKAhFmbnUkUfcqRq7YE69xqodumza1SCBclM07EWVTIxthyRm36kHJsRq BRgj+CUzuru8tW7ICKtSUTbMNP5BwkM= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1744193387; a=rsa-sha256; cv=none; b=Pbh3twM+KygR023a7D0fqkD77CHg0VBUwzYc0/HzWMUWTZi5PWQUw3IP3h5WQjLnNj1BJc DnKw4+L5csZ+LKcdWJ8DA16To4Htj+QjoyMlS8dKP0Er2l80qL5kCzol1PlF1um1TNCimq ZmKyEeZNxYIh1IomznOC0RrAEKyBKdo= ARC-Authentication-Results: i=1; imf23.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=arm.com; spf=pass (imf23.hostedemail.com: domain of anshuman.khandual@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=anshuman.khandual@arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id D0B2F106F; Wed, 9 Apr 2025 03:09:46 -0700 (PDT) Received: from [10.162.42.12] (a077893.blr.arm.com [10.162.42.12]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 7E1043F59E; Wed, 9 Apr 2025 03:09:44 -0700 (PDT) Message-ID: <0ec536d2-4b82-4e97-9985-15cd431059ba@arm.com> Date: Wed, 9 Apr 2025 15:39:41 +0530 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] selftests/mm: Fix compiler -Wmaybe-uninitialized warning To: David Hildenbrand , linux-mm@kvack.org Cc: Andrew Morton , Shuah Khan , linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org References: <20250409095006.1422620-1-anshuman.khandual@arm.com> <9da46633-e9c1-42a7-b52b-16cf89836abc@redhat.com> Content-Language: en-US From: Anshuman Khandual In-Reply-To: <9da46633-e9c1-42a7-b52b-16cf89836abc@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 0D624140008 X-Stat-Signature: f3z5g5gutxdnxex8t38gki8jfomycepi X-Rspam-User: X-HE-Tag: 1744193386-236550 X-HE-Meta: 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 4/9/25 15:27, David Hildenbrand wrote: > On 09.04.25 11:50, Anshuman Khandual wrote: >> Following build warning comes up for cow test as 'transferred' variable has >> not been initialized. Fix the warning via zero init for the variable. >> >>    CC       cow >> cow.c: In function ‘do_test_vmsplice_in_parent’: >> cow.c:365:61: warning: ‘transferred’ may be used uninitialized [-Wmaybe-uninitialized] >>    365 |                 cur = read(fds[0], new + total, transferred - total); >>        |                                                 ~~~~~~~~~~~~^~~~~~~ >> cow.c:296:29: note: ‘transferred’ was declared here >>    296 |         ssize_t cur, total, transferred; >>        |                             ^~~~~~~~~~~ >>    CC       compaction_test >>    CC       gup_longterm >> >> Cc: Andrew Morton >> Cc: Shuah Khan >> Cc: linux-mm@kvack.org >> Cc: linux-kselftest@vger.kernel.org >> Cc: linux-kernel@vger.kernel.org >> Signed-off-by: Anshuman Khandual >> --- >>   tools/testing/selftests/mm/cow.c | 2 +- >>   1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/tools/testing/selftests/mm/cow.c b/tools/testing/selftests/mm/cow.c >> index f0cb14ea8608..b6cfe0a4b7df 100644 >> --- a/tools/testing/selftests/mm/cow.c >> +++ b/tools/testing/selftests/mm/cow.c >> @@ -293,7 +293,7 @@ static void do_test_vmsplice_in_parent(char *mem, size_t size, >>           .iov_base = mem, >>           .iov_len = size, >>       }; >> -    ssize_t cur, total, transferred; >> +    ssize_t cur, total, transferred = 0; >>       struct comm_pipes comm_pipes; >>       char *old, *new; >>       int ret, fds[2]; > > > if (before_fork) { >     transferred = vmsplice(fds[1], &iov, 1, 0); > ... > > if (!before_fork) { >     transferred = vmsplice(fds[1], &iov, 1, 0); > ... > > for (total = 0; total < transferred; total += cur) { > ... > > > And I don't see any jump label that could jump to code that would ve using transferred. > > What am I missing? Probably because both those conditional statements are not mutually exclusive above with an if-else construct. Hence compiler flags it rather as a false positive ? Initializing with 0 just works around that false positive.