From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp62.i.mail.ru (smtp62.i.mail.ru [217.69.128.42]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dev.tarantool.org (Postfix) with ESMTPS id A5D01469710 for ; Tue, 19 May 2020 16:21:12 +0300 (MSK) Date: Tue, 19 May 2020 13:21:11 +0000 From: Nikita Pettik Message-ID: <20200519132111.GB12739@tarantool.org> References: <22a830fb9d2dbc3883b9710d36ab88c638101002.1589240704.git.v.shpilevoy@tarantool.org> <20200513123145.GA16814@tarantool.org> <06c4d5d9-db84-4043-0d7a-81c0320b6663@tarantool.org> <20200514023242.GE18509@tarantool.org> <27e7c364-8242-6c7b-c38c-0ad578e4977e@tarantool.org> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <27e7c364-8242-6c7b-c38c-0ad578e4977e@tarantool.org> Subject: Re: [Tarantool-patches] [PATCH 4/5] error: provide MP_ERROR extension serializer List-Id: Tarantool development patches List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Vladislav Shpilevoy Cc: tarantool-patches@dev.tarantool.org On 14 May 23:28, Vladislav Shpilevoy wrote: > Hi! Thanks for the review! > > >>> /** > >>> * MP_ERROR extension string serializer. > >>> * There are two applications for string serialization - into a > >>> * buffer, and into a file. Structure of both is exactly the same > >>> * except for the copying/writing itself. To avoid code > >>> * duplication the code is templated and expects some macros to do > >>> * the actual output. > >>> */ > >> This is basically a C template. The same as bps tree, rb tree, mhash. But > >> located in the same source file which needs it. Since this is not a common > >> enough feature to move it to a separate place. > >> > >> I include self with pre-declared macros MP_ERROR_PRINT_DEFINITION. When it > >> is defined, the file skips everything except the 3 functions in the end: > >> mp_print_error_one(), mp_print_error_stack(), mp_print_error(). > > > > A-ha, it is what I missed. But personally I would anyway move these > > macros/functions to a separate file. It would definitely cut extra > > questions and would make code cleaner (IMHO) (I bet anybody who > > sees '#include __FILE__' for the first time is like 'WTF?!'). > > But! How cool the self inclusion is 😎. If someone would wrap these things > into neat macros, it could be a useful tool to replace C++ templates, which > are the only real problem on the way of getting rid of C++ from the code base. > For example, tuple comparators heavily depend on templates, and their move > to separate files is hardly possible - they depend on tuple_compare.cc > internals too much. > > Jokes aside, self inclusion solves one important issue - non templated > dependencies. If I move the templates to a different file, it needs to include > "mp_error.h", at least for MP_ERROR_* enum constants. Strictly speaking. Also > it needs MessagePack headers, and can't use any mp_error.cc internal functions > even though these templates *are* internal too. Ok, as you wish. > >> The skip uses mere #ifdef MP_ERROR_PRINT_DEFINITION to understand, that > >> currently the file is being included into self to customize the error > >> printers. So all is skipped except them. > >> > >> I include the file twice, but with different parameters. Like if I would > >> customize one template with two parameter sets in C++. First inclusion > >> turns > >> > >> mp_print_error_one(), mp_print_error_stack(), mp_print_error() > >> > >> into > >> > >> mp_snprint_error_one(), mp_snprint_error_stack(), mp_snprint_error() > >> > >> and snprintf() calls inside. The second inclusion turns the functions into > >> > >> mp_fprint_error_one(), mp_fprint_error_stack(), mp_fprint_error() > >> > >> and fprintf() calls inside. > >> > >> I tried to extend the comment. > > > > You gave cool explanation right in this message. Why not copy it to > > the source file? > > Because it is too common. Can't put it in just one place, since the mentioned > things are spread on the file. I tried to split it in parts and put them > where they belong. In addition to the comment I added previously. Ok, thanks. LGTM. > diff --git a/src/box/mp_error.cc b/src/box/mp_error.cc > index a4a4ccaca..23a74d0a9 100644 > --- a/src/box/mp_error.cc > +++ b/src/box/mp_error.cc > @@ -28,6 +28,11 @@ > * THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF > * SUCH DAMAGE. > */ > +/** > + * When this macros is defined, it means the file included self in > + * order to customize some templates. Skip everything except them > + * then. > + */ > #ifndef MP_ERROR_PRINT_DEFINITION > > #include "box/mp_error.h" > @@ -556,6 +561,11 @@ error_unpack_unsafe(const char **data) > return err; > } > > +/** > + * Include this file into self with a few template parameters > + * to create mp_snprint_error() and mp_fprint_error() functions > + * and their helpers from a printer template. > + */ > #define MP_ERROR_PRINT_DEFINITION > #define MP_PRINT_FUNC snprintf > #define MP_PRINT_SUFFIX snprint > @@ -675,6 +685,11 @@ mp_print_error_stack(MP_PRINT_ARGS_DECL, const char **data, int depth) > return total; > } > > +/** > + * The main printer template. Depending on template parameters it > + * is turned into mp_snprint_error() with snprintf() semantics or > + * into mp_fprint_error() with fprintf() semantics. > + */ > int > mp_print_error(MP_PRINT_ARGS_DECL, const char **data, int depth) > {