From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp39.i.mail.ru (smtp39.i.mail.ru [94.100.177.99]) (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 AA56545C304 for ; Wed, 9 Dec 2020 12:04:48 +0300 (MSK) References: From: Artem Message-ID: <915844be-a960-d7af-3eed-acc0ea8f9872@tarantool.org> Date: Wed, 9 Dec 2020 12:04:47 +0300 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8"; format="flowed" Content-Transfer-Encoding: 8bit Content-Language: ru Subject: Re: [Tarantool-patches] [PATCH v2 1/2] sql: fix build with GCC 10 List-Id: Tarantool development patches List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Leonid Vasiliev Cc: tarantool-patches@dev.tarantool.org Hi, thanks for your letter! Answering your question: we can't just return NULL, because this function, oddly enough, is responsible for clearing of its arguments in case of allocation failure. In order to clean them correctly we need to fill `Select` structure and invoke `clearSelect` for it. 09.12.2020 11:43, Leonid Vasiliev пишет: > Hi! Thank you for the patch. > Looks correctly, but I have one question: > > On 27.11.2020 15:43, Artem Starshov via Tarantool-patches wrote: >> GCC 10 produces the following error: >> cc1: warning: function may return address of local variable >> [-Wreturn-local-addr] >> >> Fix it. >> >> Part-of #4966 >> --- >> Got LGTM from Nikita Pettik: >> https://lists.tarantool.org/pipermail/tarantool-patches/2020-November/020940.html >> >> >>   src/box/sql/select.c | 56 ++++++++++++++++++++------------------------ >>   1 file changed, 26 insertions(+), 30 deletions(-) >> >> diff --git a/src/box/sql/select.c b/src/box/sql/select.c >> index b0554a172..5d4b2f624 100644 >> --- a/src/box/sql/select.c >> +++ b/src/box/sql/select.c >> @@ -154,56 +154,52 @@ sqlSelectNew(Parse * pParse,    /* Parsing >> context */ >>            Expr * pLimit,        /* LIMIT value.  NULL means not used */ >>            Expr * pOffset)    /* OFFSET value.  NULL means no offset */ >>   { >> -    Select *pNew; >>       Select standin; >>       sql *db = pParse->db; >> -    pNew = sqlDbMallocRawNN(db, sizeof(*pNew)); >> -    if (pNew == 0) { > > 1) Why can't we return NULL if malloc has failed and don't work with > standin at all? > >> -        assert(db->mallocFailed); >> -        pNew = &standin; >> -    } >>       if (pEList == 0) { >>           struct Expr *expr = sql_expr_new_anon(db, TK_ASTERISK); >>           if (expr == NULL) >>               pParse->is_aborted = true; >>           pEList = sql_expr_list_append(db, NULL, expr); >>       } >> -    pNew->pEList = pEList; >> -    pNew->op = TK_SELECT; >> -    pNew->selFlags = selFlags; >> -    pNew->iLimit = 0; >> -    pNew->iOffset = 0; >> +    standin.pEList = pEList; >> +    standin.op = TK_SELECT; >> +    standin.selFlags = selFlags; >> +    standin.iLimit = 0; >> +    standin.iOffset = 0; >>   #ifdef SQL_DEBUG >> -    pNew->zSelName[0] = 0; >> +    standin.zSelName[0] = 0; >>       if ((pParse->sql_flags & SQL_SelectTrace) != 0) >>           sqlSelectTrace = 0xfff; >>       else >>           sqlSelectTrace = 0; >>   #endif >> -    pNew->addrOpenEphm[0] = -1; >> -    pNew->addrOpenEphm[1] = -1; >> -    pNew->nSelectRow = 0; >> +    standin.addrOpenEphm[0] = -1; >> +    standin.addrOpenEphm[1] = -1; >> +    standin.nSelectRow = 0; >>       if (pSrc == 0) >>           pSrc = sqlDbMallocZero(db, sizeof(*pSrc)); >> -    pNew->pSrc = pSrc; >> -    pNew->pWhere = pWhere; >> -    pNew->pGroupBy = pGroupBy; >> -    pNew->pHaving = pHaving; >> -    pNew->pOrderBy = pOrderBy; >> -    pNew->pPrior = 0; >> -    pNew->pNext = 0; >> -    pNew->pLimit = pLimit; >> -    pNew->pOffset = pOffset; >> -    pNew->pWith = 0; >> +    standin.pSrc = pSrc; >> +    standin.pWhere = pWhere; >> +    standin.pGroupBy = pGroupBy; >> +    standin.pHaving = pHaving; >> +    standin.pOrderBy = pOrderBy; >> +    standin.pPrior = 0; >> +    standin.pNext = 0; >> +    standin.pLimit = pLimit; >> +    standin.pOffset = pOffset; >> +    standin.pWith = 0; >>       assert(pOffset == 0 || pLimit != 0 || pParse->is_aborted >>              || db->mallocFailed != 0); >> +    Select *pNew = sqlDbMallocRawNN(db, sizeof(*pNew)); >>       if (db->mallocFailed) { >> -        clearSelect(db, pNew, pNew != &standin); >> -        pNew = 0; >> -    } else { >> -        assert(pNew->pSrc != 0 || pParse->is_aborted); >> +        clearSelect(db, &standin, 0); >> +        if (pNew != NULL) >> +            sqlDbFree(db, pNew); >> +        return NULL; >>       } >> -    assert(pNew != &standin); >> +    assert(standin.pSrc != 0 || pParse->is_aborted); >> +    memcpy(pNew, &standin, sizeof(standin)); >>       return pNew; >>   } >>