From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from localhost (localhost [127.0.0.1]) by turing.freelists.org (Avenir Technologies Mail Multiplex) with ESMTP id E3DA42772C for ; Mon, 16 Jul 2018 08:49:49 -0400 (EDT) Received: from turing.freelists.org ([127.0.0.1]) by localhost (turing.freelists.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id pVVRTcsA72lI for ; Mon, 16 Jul 2018 08:49:49 -0400 (EDT) Received: from smtp37.i.mail.ru (smtp37.i.mail.ru [94.100.177.97]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by turing.freelists.org (Avenir Technologies Mail Multiplex) with ESMTPS id 9F53027728 for ; Mon, 16 Jul 2018 08:49:49 -0400 (EDT) Date: Mon, 16 Jul 2018 15:49:50 +0300 From: Alexander Turenko Subject: [tarantool-patches] Re: [PATCH v1 1/1] lua: fix strange behaviour of tonumber64 Message-ID: <20180716124949.3uhj5zrkivphdnaw@tkn_work_nb> References: <6b638fd3-58bc-2ed7-c32c-3f0a440d1f2b@tarantool.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <6b638fd3-58bc-2ed7-c32c-3f0a440d1f2b@tarantool.org> Sender: tarantool-patches-bounce@freelists.org Errors-to: tarantool-patches-bounce@freelists.org Reply-To: tarantool-patches@freelists.org List-help: List-unsubscribe: List-software: Ecartis version 1.0.0 List-Id: tarantool-patches List-subscribe: List-owner: List-post: List-archive: To: Vladislav Shpilevoy Cc: Kirill Shcherbatov , tarantool-patches@freelists.org Hi, Vlad! That is interesting discussion. Hope you don't mind my participation. WBR, Alexander Turenko. On Mon, Jul 16, 2018 at 01:23:36PM +0300, Vladislav Shpilevoy wrote: > Thanks for the patch! See 4 comments below. > > On 13/07/2018 14:21, Kirill Shcherbatov wrote: > > Function tonumber64 has worked incorrectly with values less > > than LLONG_MIN. > > Now it works in the interval [LLONG_MIN, ULLONG_MAX] returning > > nil otherwise. > > > > Closes #3466. > > --- > > Branch: https://github.com/tarantool/tarantool/compare/kshch/gh-3466-tonumber64-strange-behaviour > > Issue: https://github.com/tarantool/tarantool/issues/3466 > > > > src/lua/init.c | 6 +++++- > > test/box/misc.result | 19 +++++++++++++++++++ > > test/box/misc.test.lua | 8 ++++++++ > > 3 files changed, 32 insertions(+), 1 deletion(-) > > > > diff --git a/src/lua/init.c b/src/lua/init.c > > index 9a96030..4b5285d 100644 > > --- a/src/lua/init.c > > +++ b/src/lua/init.c > > @@ -222,7 +222,11 @@ lbox_tonumber64(struct lua_State *L) > > if (argl == 0) { > > lua_pushnil(L); > > } else if (negative) { > > - luaL_pushint64(L, -1 * (long long )result); > > + if (result > -((unsigned long long )LLONG_MIN)) { > > 1. Please, do not enclose one-line bodies into {}. > > 2. How can you cast LLONG_MIN (that is negative) to the unsigned type? > Cast does not change bits. It is legal. > 3. Why not 'result > LLONG_MAX'? As I understand, abs(LLONG_MAX) == abs(LLONG_MIN), > it is not? (http://www.cplusplus.com/reference/climits/) > No, LLONG_MAX is 2^63-1, but LLONG_MIN is -2^63. We want to compare result with 2^63. We are trying to do so in platform-independent way (hovewer unsiged unary nimus equivalence with signed one is likely two-complement number representation property and can be violated on other platforms). Are you think we should introduce our own constant 9223372036854775808ULL (2^63) and avoid that complex assumptions set? It would be explicitly number-representation-dependent, so maybe it is better. > 4. Why the function is named to64, but we use non-explicitly sized types? > I mean, why not to use uint64_t result, compare with INT64_MAX etc. According to > the C standard, LLONG_MAX is not restricted with 64 bits. > Yep, it is better to use INT64_MIN from stdint.h.