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[86.180.62.188]) by smtp.gmail.com with ESMTPSA id u6sm25258694wrm.90.2020.12.12.14.18.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 12 Dec 2020 14:18:39 -0800 (PST) Date: Sat, 12 Dec 2020 22:18:39 +0000 From: Andrew Burgess To: Simon Marchi Subject: Re: [PUSHED] gdb/fortran: Support negative array stride in one limited case Message-ID: <20201212221839.GF2945@embecosm.com> References: <87eev9kn0u.fsf@redhat.com> <20200225163500.13749-1-andrew.burgess@embecosm.com> <62551675-7b8d-a6af-113e-d59ad6c2334f@polymtl.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <62551675-7b8d-a6af-113e-d59ad6c2334f@polymtl.ca> X-Operating-System: Linux/5.8.13-100.fc31.x86_64 (x86_64) X-Uptime: 22:16:57 up 4 days, 3:01, X-Editor: GNU Emacs [ http://www.gnu.org/software/emacs ] X-BeenThere: gdb-patches@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gdb-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: gdb-patches@sourceware.org Errors-To: gdb-patches-bounces@sourceware.org Sender: "Gdb-patches" * Simon Marchi [2020-12-12 01:33:21 -0500]: > Hi Andrew, > > Sorry to revive this thread. > > I build my GDB with ASan, and I see the gdb.fortran/vla-type.exp test crashing GDB with: > > ptype fivedynarr(2) > /home/smarchi/src/binutils-gdb/gdb/valarith.c:1171:10: runtime error: signed integer overflow: 16777216 * 140737351048816 cannot be represented in type 'long int' > > Commit 5bbd8269fa8d ("gdb/fortran: array stride support") is the first one where it does Thanks for bringing this to my attention. I'll take a look at this next week. Andrew > this. > > Simon > > On 2020-02-25 11:35 a.m., Andrew Burgess wrote: > > I've pushed this fix now. The exact patch I pushed is included below. > > > > > > Thanks, > > Andrew > > > > > > > > > > --- > > > > This commit adds support for negative Fortran array strides in one > > limited case, that is the case of a single element array with a > > negative array stride. > > > > The changes in this commit will be required in order for more general > > negative array stride support to work correctly, however, right now > > other problems in GDB prevent negative array strides from working in > > the general case. > > > > The reason negative array strides don't currently work in the general > > case is that when dealing with such arrays, the base address for the > > objects data is actually the highest addressed element, subsequent > > elements are then accessed with a negative offset from that address, > > and GDB is not currently happy with this configuration. > > > > The changes here can be summarised as, stop treating signed values as > > unsigned, specifically, the array stride, and offsets calculated using > > the array stride. > > > > This issue was identified on the mailing list by Sergio: > > > > https://sourceware.org/ml/gdb-patches/2020-01/msg00360.html > > > > The test for this issue is a new one written by me as the copyright > > status of the original test is currently unknown. > > > > gdb/ChangeLog: > > > > * gdbtypes.c (create_array_type_with_stride): Handle negative > > array strides. > > * valarith.c (value_subscripted_rvalue): Likewise. > > > > gdb/testsuite/ChangeLog: > > > > * gdb.fortran/derived-type-striding.exp: Add a new test. > > * gdb.fortran/derived-type-striding.f90: Add pointer variable for > > new test. > > --- > > gdb/ChangeLog | 6 ++++++ > > gdb/gdbtypes.c | 17 +++++++++++++---- > > gdb/testsuite/ChangeLog | 6 ++++++ > > gdb/testsuite/gdb.fortran/derived-type-striding.exp | 2 ++ > > gdb/testsuite/gdb.fortran/derived-type-striding.f90 | 2 ++ > > gdb/valarith.c | 4 ++-- > > 6 files changed, 31 insertions(+), 6 deletions(-) > > > > diff --git a/gdb/gdbtypes.c b/gdb/gdbtypes.c > > index 85758930491..ef110b30445 100644 > > --- a/gdb/gdbtypes.c > > +++ b/gdb/gdbtypes.c > > @@ -1223,7 +1223,7 @@ create_array_type_with_stride (struct type *result_type, > > && !type_not_allocated (result_type))) > > { > > LONGEST low_bound, high_bound; > > - unsigned int stride; > > + int stride; > > > > /* If the array itself doesn't provide a stride value then take > > whatever stride the range provides. Don't update BIT_STRIDE as > > @@ -1241,9 +1241,18 @@ create_array_type_with_stride (struct type *result_type, > > In such cases, the array length should be zero. */ > > if (high_bound < low_bound) > > TYPE_LENGTH (result_type) = 0; > > - else if (stride > 0) > > - TYPE_LENGTH (result_type) = > > - (stride * (high_bound - low_bound + 1) + 7) / 8; > > + else if (stride != 0) > > + { > > + /* Ensure that the type length is always positive, even in the > > + case where (for example in Fortran) we have a negative > > + stride. It is possible to have a single element array with a > > + negative stride in Fortran (this doesn't mean anything > > + special, it's still just a single element array) so do > > + consider that case when touching this code. */ > > + LONGEST element_count = abs (high_bound - low_bound + 1); > > + TYPE_LENGTH (result_type) > > + = ((abs (stride) * element_count) + 7) / 8; > > + } > > else > > TYPE_LENGTH (result_type) = > > TYPE_LENGTH (element_type) * (high_bound - low_bound + 1); > > diff --git a/gdb/testsuite/gdb.fortran/derived-type-striding.exp b/gdb/testsuite/gdb.fortran/derived-type-striding.exp > > index 094843ca8b1..639dc4c9528 100644 > > --- a/gdb/testsuite/gdb.fortran/derived-type-striding.exp > > +++ b/gdb/testsuite/gdb.fortran/derived-type-striding.exp > > @@ -41,3 +41,5 @@ gdb_test "p point_dimension" "= \\\(2, 2, 2, 2, 2, 2, 2, 2, 2\\\)" > > # Test mixed type derived type. > > if { $gcc_with_broken_stride } { setup_kfail *-*-* gcc/92775 } > > gdb_test "p point_mixed_dimension" "= \\\(3, 3, 3, 3\\\)" > > + > > +gdb_test "p cloud_slice" " = \\\(\\\( x = 1, y = 2, z = 3 \\\)\\\)" > > diff --git a/gdb/testsuite/gdb.fortran/derived-type-striding.f90 b/gdb/testsuite/gdb.fortran/derived-type-striding.f90 > > index 26829f51dc0..fb537579faa 100644 > > --- a/gdb/testsuite/gdb.fortran/derived-type-striding.f90 > > +++ b/gdb/testsuite/gdb.fortran/derived-type-striding.f90 > > @@ -28,9 +28,11 @@ program derived_type_member_stride > > type(mixed_cartesian), dimension(10), target :: mixed_cloud > > integer(kind=8), dimension(:), pointer :: point_dimension => null() > > integer(kind=8), dimension(:), pointer :: point_mixed_dimension => null() > > + type(cartesian), dimension(:), pointer :: cloud_slice => null() > > cloud(:)%x = 1 > > cloud(:)%y = 2 > > cloud(:)%z = 3 > > + cloud_slice => cloud(3:2:-2) > > point_dimension => cloud(1:9)%y > > mixed_cloud(:)%x = 1 > > mixed_cloud(:)%y = 2 > > diff --git a/gdb/valarith.c b/gdb/valarith.c > > index 79b148602bb..be0e0731bee 100644 > > --- a/gdb/valarith.c > > +++ b/gdb/valarith.c > > @@ -187,7 +187,7 @@ value_subscripted_rvalue (struct value *array, LONGEST index, LONGEST lowerbound > > { > > struct type *array_type = check_typedef (value_type (array)); > > struct type *elt_type = check_typedef (TYPE_TARGET_TYPE (array_type)); > > - ULONGEST elt_size = type_length_units (elt_type); > > + LONGEST elt_size = type_length_units (elt_type); > > > > /* Fetch the bit stride and convert it to a byte stride, assuming 8 bits > > in a byte. */ > > @@ -199,7 +199,7 @@ value_subscripted_rvalue (struct value *array, LONGEST index, LONGEST lowerbound > > elt_size = stride / (unit_size * 8); > > } > > > > - ULONGEST elt_offs = elt_size * (index - lowerbound); > > + LONGEST elt_offs = elt_size * (index - lowerbound); > > > > if (index < lowerbound > > || (!TYPE_ARRAY_UPPER_BOUND_IS_UNDEFINED (array_type) > >