Path: ...!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!eternal-september.org!.POSTED!not-for-mail From: Julio Di Egidio Newsgroups: comp.lang.c Subject: Re: So You Think You Can Const? Date: Wed, 15 Jan 2025 13:56:12 +0100 Organization: A noiseless patient Spider Lines: 106 Message-ID: References: <20250107130809.661@kylheku.com> <87a5c15ob0.fsf@bsb.me.uk> <87ldvk4wu7.fsf@bsb.me.uk> <20250108200758.563@kylheku.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Injection-Date: Wed, 15 Jan 2025 13:56:14 +0100 (CET) Injection-Info: dont-email.me; posting-host="2563c1350cfe2ddd1cd2f0f3cf044725"; logging-data="3106880"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1+54PG4kOLQWBxMGvUYCK9QAOphFPiVBrw=" User-Agent: Mozilla Thunderbird Cancel-Lock: sha1:z7LufSL+B9TXCd/JYcPpyZaD92w= Content-Language: en-GB In-Reply-To: Bytes: 4786 On 09/01/2025 10:35, David Brown wrote: > On 09/01/2025 05:24, Kaz Kylheku wrote: >> On 2025-01-09, Ben Bacarisse wrote: >>> Julio Di Egidio writes: >>> >>>> static AvlTree_t const *AvlTree_node( >>>>      void const *pk, AvlTree_t const *pL, AvlTree_t const *pR >>>> ) { >>>>      AvlTree_t *pT; >>>> >>>>      pT = malloc(sizeof(AvlTree_t)); >>>> >>>>      if (!pT) { >>>>          return NULL; >>>>      } >>>> >>>>      pT->pk = pk; >>>>      pT->pL = pL; >>>>      pT->pR = pR; >>>> >>>>      return pT; >>>> } >>> >>> Just on a side issue, I prefer to make tests like this positive so I'd >>> write: >>> >>>   static AvlTree_t const *AvlTree_node( >>>       void const *pk, AvlTree_t const *pL, AvlTree_t const *pR >>>   ) { >>>       AvlTree_t *pT = malloc(*pT); >>>       if (pT) { >>>           pT->pk = pk; >>>           pT->pL = pL; >>>           pT->pR = pR; >>>       } >>>       return pT; >>>   } >> >> More generally: >> >>     foo_handle *foo = foo_create(); >>     bar_handle *bar = foo ? bar_create(foo) : 0; // doesn't like null >>     xyzzy_handle *xyz = xyzzy_create(42, bar, arg); >>     container *con = malloc(sizeof *con); >> >>     if (foo && bar && xyz && con) { >>       // happy case: we have all three resources >> >>       con->foo = foo; >>       con->bar = bar; >>       con->xyz = xyz; >> >>       return con; >>     } >> >>     xyzzy_destroy(xyz); >>     xyzzy_destroy(bar); >>     if (foo) >>        xyzzy_destroy(foo); // stupidly doesn't like null >> >>     return 0; >> >>> I'm not going to "make a case" for this (though I will if you want!) -- >>> I just think it helps to see lots of different styles. >> >> I might just have made the case. When more resources need to be >> acquired that might fail, it consolidates the happy case under one >> conjunctive test, and consolidates the cleanup in the unhappy case. >> Effectively it's almost if we have only two cases. >> >> A minor disadvantage is that in the unhappy flow, we may allocate >> resources past the point where it is obvious they are not going to be >> needed: if foo_create() failed, we are pointlessly calling >> xyzzy_create() and malloc for the container. It's possible that these >> succeed, and we are just going to turn around and free them. >> > > How about taking the idea slightly further and making the later > allocations conditional too? > >    foo_handle *foo = foo_create(); >    bar_handle *bar = foo ? bar_create(foo) : 0; // doesn't like null >    xyzzy_handle *xyz = bar ? xyzzy_create(42, bar, arg) : 0; >    container *con = xyz ? malloc(sizeof *con) : 0; > >    if (con) { >      // happy case: we have all three resources > >    ... > > If you are going to use that style (and I not arguing for or against > it), go all in! > > >> It's a form of consolidated error checking, like when we make >> several system calls and check them for errors as a batch; >> e.g. call fprintf several times and check for disk full (etc) >> just once. HOW about you and that piece of nazi-retarded shit rather go fuck yourself somewhere else? Eh?? Yeah, that would be it: I am having a great idea: YOU GO fuck yourself out of cpomp.lang.cv !! I am a fucking genius... -Julio