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 lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 1DAA8EB7EAC for ; Wed, 4 Mar 2026 09:59:46 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1vxj0e-0006XG-C8; Wed, 04 Mar 2026 04:59:16 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1vxj0c-0006Wt-LW for qemu-devel@nongnu.org; Wed, 04 Mar 2026 04:59:14 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1vxj0a-0004UE-Ug for qemu-devel@nongnu.org; Wed, 04 Mar 2026 04:59:14 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1772618351; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=XwaJZGUrc3/GtI8IhGfByEsnwYSAa4z44LKHfN6Q6+Q=; b=cKGJm6mvCwE3t9y7FyIyVeoKNRniO7J0tMGQqtI+BdZb7wM1N7Cmdnj8U8NWwn7v6O8I9I v+uO2xPVfeAcYu9N3TXE44+YumqyBsdYIpqkK8GLZrW6ALrBZfISrBgtEgX6poQMEpAN03 z/A8dhCQuhKilmLdoyqRhNgSYrLqA90= Received: from mx-prod-mc-01.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-612-w82f1UEROtKM0QySErnSSg-1; Wed, 04 Mar 2026 04:59:08 -0500 X-MC-Unique: w82f1UEROtKM0QySErnSSg-1 X-Mimecast-MFC-AGG-ID: w82f1UEROtKM0QySErnSSg_1772618347 Received: from mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.93]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 6A6CE1955D9C; Wed, 4 Mar 2026 09:59:05 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.45.242.30]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 9AD50180049D; Wed, 4 Mar 2026 09:59:03 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 420FC21E692F; Wed, 04 Mar 2026 10:59:01 +0100 (CET) From: Markus Armbruster To: Akihiko Odaki Cc: qemu-devel@nongnu.org, Viktor Prutyanov , Alex Williamson , =?utf-8?Q?C=C3=A9dric?= Le Goater , Michael Roth , Paolo Bonzini , =?utf-8?Q?Marc-Andr=C3=A9?= Lureau , Daniel P. =?utf-8?Q?Berrang=C3=A9?= , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , Keith Busch , Klaus Jensen , Jesper Devantier , qemu-block@nongnu.org Subject: Re: [PATCH v3 3/4] tests: Avoid sprintf() with "%.6f" In-Reply-To: <20260304-nvme-v3-3-bbb1b7fd2d0b@rsg.ci.i.u-tokyo.ac.jp> (Akihiko Odaki's message of "Wed, 04 Mar 2026 15:28:35 +0900") References: <20260304-nvme-v3-0-bbb1b7fd2d0b@rsg.ci.i.u-tokyo.ac.jp> <20260304-nvme-v3-3-bbb1b7fd2d0b@rsg.ci.i.u-tokyo.ac.jp> Date: Wed, 04 Mar 2026 10:59:01 +0100 Message-ID: <87wlzrkja2.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 Received-SPF: pass client-ip=170.10.133.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: 27 X-Spam_score: 2.7 X-Spam_bar: ++ X-Spam_report: (2.7 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_SBL_CSS=3.335, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.322, RCVD_IN_VALIDITY_SAFE_BLOCKED=1.141, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Akihiko Odaki writes: > A string that represents a double can be long if it is an exponentially > large number. I'd like us to spell out that this is cleanup, not a bug fix. I suggest to start with the warning. Something like this: tests: Clean up double comparisons to avoid compiler warning To enable -Wformat-overflow=2, we need to clean up a couple of false positives: Now explain why they are false: These buffers cannot actually overflow because the doubles are between 0 and 31.0/3 inclusive. Then justify the solution: However, formatting doubles just to compare them is silly. Compare them directly instead. To avoid potential rounding trouble, change the numbers tested to be representable exactly in double. > Signed-off-by: Akihiko Odaki > --- > tests/unit/test-qobject-input-visitor.c | 8 ++------ > tests/unit/test-qobject-output-visitor.c | 7 ++----- > 2 files changed, 4 insertions(+), 11 deletions(-) > > diff --git a/tests/unit/test-qobject-input-visitor.c b/tests/unit/test-qobject-input-visitor.c > index 84bdcdf702e0..beee11db4e47 100644 > --- a/tests/unit/test-qobject-input-visitor.c > +++ b/tests/unit/test-qobject-input-visitor.c > @@ -500,7 +500,7 @@ static void test_visitor_in_list_struct(TestInputVisitorData *data, > g_string_append_printf(json, "'number': ["); > sep = ""; > for (i = 0; i < 32; i++) { > - g_string_append_printf(json, "%s%f", sep, (double)i / 3); > + g_string_append_printf(json, "%s%f", sep, (double)i / FLT_RADIX); > sep = ", "; > } > g_string_append_printf(json, "], "); > @@ -583,11 +583,7 @@ static void test_visitor_in_list_struct(TestInputVisitorData *data, > > i = 0; > for (num_list = arrs->number; num_list; num_list = num_list->next) { > - char expected[32], actual[32]; > - > - sprintf(expected, "%.6f", (double)i / 3); > - sprintf(actual, "%.6f", num_list->value); > - g_assert_cmpstr(expected, ==, actual); > + g_assert_cmpfloat(num_list->value, ==, (double)i / FLT_RADIX); > i++; > } > > diff --git a/tests/unit/test-qobject-output-visitor.c b/tests/unit/test-qobject-output-visitor.c > index 407ab9ed505a..3c47b28f6638 100644 > --- a/tests/unit/test-qobject-output-visitor.c > +++ b/tests/unit/test-qobject-output-visitor.c > @@ -538,7 +538,7 @@ static void test_visitor_out_list_struct(TestOutputVisitorData *data, > } > > for (i = 31; i >= 0; i--) { > - QAPI_LIST_PREPEND(arrs->number, (double)i / 3); > + QAPI_LIST_PREPEND(arrs->number, (double)i / FLT_RADIX); > } > > for (i = 31; i >= 0; i--) { > @@ -571,12 +571,9 @@ static void test_visitor_out_list_struct(TestOutputVisitorData *data, > i = 0; > QLIST_FOREACH_ENTRY(qlist, e) { > QNum *qvalue = qobject_to(QNum, qlist_entry_obj(e)); > - char expected[32], actual[32]; > > g_assert(qvalue); > - sprintf(expected, "%.6f", (double)i / 3); > - sprintf(actual, "%.6f", qnum_get_double(qvalue)); > - g_assert_cmpstr(actual, ==, expected); > + g_assert_cmpfloat(qnum_get_double(qvalue), ==, (double)i / FLT_RADIX); > i++; > } With an improved commit message Reviewed-by: Markus Armbruster