From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 2657 invoked by alias); 13 Dec 2011 22:19:01 -0000 Received: (qmail 2642 invoked by uid 22791); 13 Dec 2011 22:19:00 -0000 X-SWARE-Spam-Status: No, hits=-2.9 required=5.0 tests=ALL_TRUSTED,AWL,BAYES_00 X-Spam-Check-By: sourceware.org Received: from localhost (HELO gcc.gnu.org) (127.0.0.1) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Tue, 13 Dec 2011 22:18:47 +0000 From: "burnus at gcc dot gnu.org" To: gcc-bugs@gcc.gnu.org Subject: [Bug fortran/51529] [OOP] gfortran.dg/class_to_type_1.f03 is miscompiled: Uninitialized variable used Date: Tue, 13 Dec 2011 22:23:00 -0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: fortran X-Bugzilla-Keywords: wrong-code X-Bugzilla-Severity: normal X-Bugzilla-Who: burnus at gcc dot gnu.org X-Bugzilla-Status: UNCONFIRMED X-Bugzilla-Priority: P3 X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org X-Bugzilla-Target-Milestone: --- X-Bugzilla-Changed-Fields: Message-ID: In-Reply-To: References: X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/ Auto-Submitted: auto-generated Content-Type: text/plain; charset="UTF-8" MIME-Version: 1.0 Mailing-List: contact gcc-bugs-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-bugs-owner@gcc.gnu.org X-SW-Source: 2011-12/txt/msg01423.txt.bz2 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51529 --- Comment #2 from Tobias Burnus 2011-12-13 22:18:44 UTC --- The problem is the following, for: allocate(t2 :: x(10)) one has: x._data.data = (void * restrict) __builtin_malloc (640); I had now expected that one would do: for (i = 1; i <= 10; i++) __builtin_memcpy ((void *) x._data, (void *) &__vtab_MAIN___T2._def_init, __vtab_MAIN___T2._size) However, the current code does: struct t2 D.1921; struct t2 t2.2; integer(kind=8) D.1919; struct t[0:] * restrict D.1918; D.1918 = (struct t[0:] * restrict) x._data.data; D.1919 = x._data.offset; t2.2.t.b.data = 0B; t2.2.z = __complex__ (3.2999999523162841796875e+0, 4.400000095367431640625e+0); D.1921 = t2.2; So far so good. That's the same as __vtab_MAIN___T2._def_init. Disadvantage: Code duplication. Advantage: The information in in the same file (translation unit). However, instead of just doing a __builtin_memcpy in a loop, one calls: __vtab_MAIN___T2._copy (&D.1921, (struct t *) D.1918 + (sizetype) ((S.3 + D.1919) * (integer(kind=8)) x._vptr->_size)); This has several disadvantages: First, makes the advantage of having all data in the same translation unit void as one calls a function, located in another translation unit. It is also much slower as _copy does many checks which we know shouldn't matter. For MOLD= or a type-spec we know that the destination does not have allocated allocatable components. However, I do now understand why one needs for SOURCE= to memset the source to NULL - at least as long _copy not only copies the data but also frees it. The latter could be also left to _free. - Actually, I am in favour of separating _copy and _free. As this issue shows, there are cases where one does not want to combine them, leading to work around actions (memset). I think only for polymorphic assignment, one needs _free + _copy, for allocate with SOURCE= a _copy should be enough. The reason for the crash is: __copy_MAIN___T2 (struct t2 & restrict src, struct t2 & restrict dst) { if (dst->t.b.data != 0B) __builtin_free ((void *) dst->t.b.data); where dst == x._data.data, where the latter and thus also x._data.data->t.b.data is filled with random memory.