From patchwork Thu Dec 14 04:53:32 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Joel Brobecker X-Patchwork-Id: 24926 Received: (qmail 42207 invoked by alias); 14 Dec 2017 04:53:39 -0000 Mailing-List: contact gdb-patches-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sourceware.org Delivered-To: mailing list gdb-patches@sourceware.org Received: (qmail 42194 invoked by uid 89); 14 Dec 2017 04:53:39 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-25.4 required=5.0 tests=AWL, BAYES_00, GIT_PATCH_0, GIT_PATCH_1, GIT_PATCH_2, GIT_PATCH_3, KAM_SHORT, RCVD_IN_DNSWL_NONE, SPF_PASS autolearn=ham version=3.3.2 spammy= X-HELO: rock.gnat.com Received: from rock.gnat.com (HELO rock.gnat.com) (205.232.38.15) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Thu, 14 Dec 2017 04:53:36 +0000 Received: from localhost (localhost.localdomain [127.0.0.1]) by filtered-rock.gnat.com (Postfix) with ESMTP id 786D1116E6C; Wed, 13 Dec 2017 23:53:35 -0500 (EST) Received: from rock.gnat.com ([127.0.0.1]) by localhost (rock.gnat.com [127.0.0.1]) (amavisd-new, port 10024) with LMTP id 5ooC87A10JmW; Wed, 13 Dec 2017 23:53:35 -0500 (EST) Received: from tron.gnat.com (tron.gnat.com [205.232.38.10]) by rock.gnat.com (Postfix) with ESMTP id 67FBB116E6B; Wed, 13 Dec 2017 23:53:35 -0500 (EST) Received: by tron.gnat.com (Postfix, from userid 4233) id 642C44A4; Wed, 13 Dec 2017 23:53:35 -0500 (EST) From: Joel Brobecker To: gdb-patches@sourceware.org Cc: Xavier Roirand Subject: [RFA/commit DWARF 1/2] Add support for dynamic DW_AT_byte_stride. Date: Wed, 13 Dec 2017 23:53:32 -0500 Message-Id: <1513227213-37871-1-git-send-email-brobecker@adacore.com> Hello, This patch adds support for DW_AT_byte_stride, using Ada as one example of where this would be useful. However, the implementation is language-agnostic. Consider the following Ada code: procedure Nested (L, U : Integer) is subtype Small_Type is Integer range L .. U; type Record_Type (I : Small_Type := L) is record S : String (1 .. I); end record; type Array_Type is array (Integer range <>) of Record_Type; A1 : Array_Type := (1 => (I => 0, S => <>), 2 => (I => 1, S => "A"), 3 => (I => 2, S => "AB")); procedure Discard (R : Record_Type) is begin null; end Discard; begin Discard (A1 (1)); -- STOP end; It defines an array A1 of Record_Type, which is a variant record type whose maximum size actually depends on the value of the parameters passed when calling Nested. As a result, the stride of the array A1 cannot be known statically, which leads the compiler to generate a dynamic DW_AT_byte_stride attribute for our type. Here is what the debugging info looks like with GNAT: .uleb128 0x10 # (DIE (0x14e) DW_TAG_array_type) .long .LASF17 # DW_AT_name: "foo__nested__T18b" .long 0x141 # DW_AT_byte_stride .long 0xdc # DW_AT_type .uleb128 0x11 # (DIE (0x15f) DW_TAG_subrange_type) .long 0x166 # DW_AT_type .byte 0x3 # DW_AT_upper_bound .byte 0 # end of children of DIE 0x14e There DW_AT_byte_stride is a reference to a local (internal) variable: .uleb128 0x9 # (DIE (0x141) DW_TAG_variable) .long .LASF6 # DW_AT_name: "foo__nested__T18b___PAD___XVZ" This patch enhances GDB to handle this dynamic byte stride attribute by first adding a new dynamic_prop_node_kind (DYN_PROP_BYTE_STRIDE) to store the array dynamic stride info (when dynamic). It then enhances the dynamic type resolver to handle this dynamic property. Before applying this patch, trying to print the value of some of A1's elements after having stopped at the "STOP" comment does not work. For instance: (gdb) p a1(2) Cannot access memory at address 0x80000268dec0 With this patch applied, GDB now prints the value of all 3 elements correctly: (gdb) print A1(1) $1 = (i => 0, s => "") (gdb) print A1(2) $2 = (i => 1, s => "A") (gdb) print A1(3) $3 = (i => 2, s => "AB") gdb/ChangeLog: * gdbtypes.h (enum dynamic_prop_node_kind) : New enum value. (create_array_type_with_stride): Add byte_stride_prop parameter. * gdbtypes.c (create_array_type_with_stride) : New parameter. Update all callers in this file. (array_type_has_dynamic_stride): New function. (is_dynamic_type_internal, resolve_dynamic_array): Add handling of arrays with dynamic byte strides. * dwarf2read.c (read_array_type): Add support for dynamic DW_AT_byte_stride attributes. gdb/testsuite/ChangeLog: * gdb.ada/dyn_stride: New testcase. Tested on x86_64-linux. This is an area where I worked quite a bit, so I feel relatively confident self approving; but I would still appreciate all comments! Thank you, diff --git a/gdb/dwarf2read.c b/gdb/dwarf2read.c index 8aed7f4..d5a55ea 100644 --- a/gdb/dwarf2read.c +++ b/gdb/dwarf2read.c @@ -16300,6 +16300,7 @@ read_array_type (struct die_info *die, struct dwarf2_cu *cu) struct type *element_type, *range_type, *index_type; struct attribute *attr; const char *name; + struct dynamic_prop *byte_stride_prop = NULL; unsigned int bit_stride = 0; element_type = die_type (die, cu); @@ -16311,7 +16312,25 @@ read_array_type (struct die_info *die, struct dwarf2_cu *cu) attr = dwarf2_attr (die, DW_AT_byte_stride, cu); if (attr != NULL) - bit_stride = DW_UNSND (attr) * 8; + { + int stride_ok; + + byte_stride_prop + = (struct dynamic_prop *) alloca (sizeof (struct dynamic_prop)); + stride_ok = attr_to_dynamic_prop (attr, die, cu, byte_stride_prop); + if (!stride_ok) + { + complaint (&symfile_complaints, + _("unable to read array DW_AT_byte_stride " + " - DIE at 0x%x [in module %s]"), + to_underlying (die->sect_off), + objfile_name (cu->objfile)); + /* Ignore this attribute. We will likely not be able to print + arrays of this type correctly, but there is little we can do + to help if we cannot read the attribute's value. */ + byte_stride_prop = NULL; + } + } attr = dwarf2_attr (die, DW_AT_bit_stride, cu); if (attr != NULL) @@ -16324,7 +16343,7 @@ read_array_type (struct die_info *die, struct dwarf2_cu *cu) index_type = objfile_type (objfile)->builtin_int; range_type = create_static_range_type (NULL, index_type, 0, -1); type = create_array_type_with_stride (NULL, element_type, range_type, - bit_stride); + byte_stride_prop, bit_stride); return set_die_type (die, type, cu); } @@ -16357,14 +16376,14 @@ read_array_type (struct die_info *die, struct dwarf2_cu *cu) while (i < range_types.size ()) type = create_array_type_with_stride (NULL, type, range_types[i++], - bit_stride); + byte_stride_prop, bit_stride); } else { size_t ndim = range_types.size (); while (ndim-- > 0) type = create_array_type_with_stride (NULL, type, range_types[ndim], - bit_stride); + byte_stride_prop, bit_stride); } /* Understand Dwarf2 support for vector types (like they occur on diff --git a/gdb/gdbtypes.c b/gdb/gdbtypes.c index 01ab6fa..6ca342b 100644 --- a/gdb/gdbtypes.c +++ b/gdb/gdbtypes.c @@ -1090,6 +1090,14 @@ discrete_position (struct type *type, LONGEST val, LONGEST *pos) Elements will be of type ELEMENT_TYPE, the indices will be of type RANGE_TYPE. + BYTE_STRIDE_PROP, when not NULL, provides the array's byte stride. + This byte stride property is added to the resulting array type + as a DYN_PROP_BYTE_STRIDE. As a consequence, the BYTE_STRIDE_PROP + argument can only be used to create types that are objfile-owned + (see add_dyn_prop), meaning that either this function must be called + with an objfile-owned RESULT_TYPE, or an objfile-owned RANGE_TYPE. + + BIT_STRIDE is taken into account only when BYTE_STRIDE_PROP is NULL. If BIT_STRIDE is not zero, build a packed array type whose element size is BIT_STRIDE. Otherwise, ignore this parameter. @@ -1101,14 +1109,27 @@ struct type * create_array_type_with_stride (struct type *result_type, struct type *element_type, struct type *range_type, + struct dynamic_prop *byte_stride_prop, unsigned int bit_stride) { + if (byte_stride_prop != NULL + && byte_stride_prop->kind == PROP_CONST) + { + /* The byte stride is actually not dynamic. Pretend we were + called with bit_stride set instead of byte_stride_prop. + This will give us the same result type, while avoiding + the need to handle this as a special case. */ + bit_stride = byte_stride_prop->data.const_val * 8; + byte_stride_prop = NULL; + } + if (result_type == NULL) result_type = alloc_type_copy (range_type); TYPE_CODE (result_type) = TYPE_CODE_ARRAY; TYPE_TARGET_TYPE (result_type) = element_type; - if (has_static_range (TYPE_RANGE_DATA (range_type)) + if (byte_stride_prop == NULL + && has_static_range (TYPE_RANGE_DATA (range_type)) && (!type_not_associated (result_type) && !type_not_allocated (result_type))) { @@ -1144,7 +1165,10 @@ create_array_type_with_stride (struct type *result_type, TYPE_FIELDS (result_type) = (struct field *) TYPE_ZALLOC (result_type, sizeof (struct field)); TYPE_INDEX_TYPE (result_type) = range_type; - if (bit_stride > 0) + if (byte_stride_prop != NULL) + add_dyn_prop (DYN_PROP_BYTE_STRIDE, *byte_stride_prop, result_type, + TYPE_OBJFILE (result_type)); + else if (bit_stride > 0) TYPE_FIELD_BITSIZE (result_type, 0) = bit_stride; /* TYPE_TARGET_STUB will take care of zero length arrays. */ @@ -1163,7 +1187,7 @@ create_array_type (struct type *result_type, struct type *range_type) { return create_array_type_with_stride (result_type, element_type, - range_type, 0); + range_type, NULL, 0); } struct type * @@ -1824,6 +1848,17 @@ stub_noname_complaint (void) complaint (&symfile_complaints, _("stub type has NULL name")); } +/* Return nonzero if TYPE has a DYN_PROP_BYTE_STRIDE dynamic property + attached to it, and that property has a non-constant value. */ + +static int +array_type_has_dynamic_stride (struct type *type) +{ + struct dynamic_prop *prop = get_dyn_prop (DYN_PROP_BYTE_STRIDE, type); + + return (prop != NULL && prop->kind != PROP_CONST); +} + /* Worker for is_dynamic_type. */ static int @@ -1869,11 +1904,16 @@ is_dynamic_type_internal (struct type *type, int top_level) { gdb_assert (TYPE_NFIELDS (type) == 1); - /* The array is dynamic if either the bounds are dynamic, - or the elements it contains have a dynamic contents. */ + /* The array is dynamic if either the bounds are dynamic... */ if (is_dynamic_type_internal (TYPE_INDEX_TYPE (type), 0)) return 1; - return is_dynamic_type_internal (TYPE_TARGET_TYPE (type), 0); + /* ... or the elements it contains have a dynamic contents... */ + if (is_dynamic_type_internal (TYPE_TARGET_TYPE (type), 0)) + return 1; + /* ... or if it has a dynamic stride... */ + if (array_type_has_dynamic_stride (type)) + return 1; + return 0; } case TYPE_CODE_STRUCT: @@ -1969,6 +2009,7 @@ resolve_dynamic_array (struct type *type, struct type *range_type; struct type *ary_dim; struct dynamic_prop *prop; + unsigned int bit_stride = 0; gdb_assert (TYPE_CODE (type) == TYPE_CODE_ARRAY); @@ -2000,8 +2041,31 @@ resolve_dynamic_array (struct type *type, else elt_type = TYPE_TARGET_TYPE (type); - return create_array_type_with_stride (type, elt_type, range_type, - TYPE_FIELD_BITSIZE (type, 0)); + prop = get_dyn_prop (DYN_PROP_BYTE_STRIDE, type); + if (prop != NULL) + { + int prop_eval_ok + = dwarf2_evaluate_property (prop, NULL, addr_stack, &value); + + if (prop_eval_ok) + { + remove_dyn_prop (DYN_PROP_BYTE_STRIDE, type); + bit_stride = (unsigned int) (value * 8); + } + else + { + /* Could be a bug in our code, but it could also happen + if the DWARF info is not correct. Issue a warning, + and assume no byte/bit stride (leave bit_stride = 0). */ + warning (_("cannot determine array stride for type %s"), + TYPE_NAME (type) ? TYPE_NAME (type) : ""); + } + } + else + bit_stride = TYPE_FIELD_BITSIZE (type, 0); + + return create_array_type_with_stride (type, elt_type, range_type, NULL, + bit_stride); } /* Resolve dynamic bounds of members of the union TYPE to static diff --git a/gdb/gdbtypes.h b/gdb/gdbtypes.h index 68ffaf8..3725462 100644 --- a/gdb/gdbtypes.h +++ b/gdb/gdbtypes.h @@ -418,6 +418,9 @@ enum dynamic_prop_node_kind /* A property representing DW_AT_allocated. The presence of this attribute indicated that the object of the type can be associated. */ DYN_PROP_ASSOCIATED, + + /* A property providing an array's byte stride. */ + DYN_PROP_BYTE_STRIDE, }; /* * List for dynamic type attributes. */ @@ -1791,7 +1794,8 @@ extern struct type *create_static_range_type (struct type *, struct type *, extern struct type *create_array_type_with_stride - (struct type *, struct type *, struct type *, unsigned int); + (struct type *, struct type *, struct type *, + struct dynamic_prop *, unsigned int); extern struct type *create_range_type (struct type *, struct type *, const struct dynamic_prop *, diff --git a/gdb/testsuite/gdb.ada/dyn_stride.exp b/gdb/testsuite/gdb.ada/dyn_stride.exp new file mode 100644 index 0000000..4dd1177 --- /dev/null +++ b/gdb/testsuite/gdb.ada/dyn_stride.exp @@ -0,0 +1,38 @@ +# Copyright 2015-2017 Free Software Foundation, Inc. +# +# This program is free software; you can redistribute it and/or modify +# it under the terms of the GNU General Public License as published by +# the Free Software Foundation; either version 3 of the License, or +# (at your option) any later version. +# +# This program is distributed in the hope that it will be useful, +# but WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +# GNU General Public License for more details. +# +# You should have received a copy of the GNU General Public License +# along with this program. If not, see . + +load_lib "ada.exp" + +standard_ada_testfile foo + +if {[gdb_compile_ada "${srcfile}" "${binfile}" executable [list debug ]] != "" } { + return -1 +} + +clean_restart ${testfile} + +set bp_location [gdb_get_line_number "STOP" ${testdir}/foo.adb] +if ![runto "foo.adb:$bp_location" ] then { + return -1 +} + +gdb_test "print A1(1)" \ + "\\(i => 0, s => \"\"\\)" + +gdb_test "print A1(2)" \ + "\\(i => 1, s => \"A\"\\)" + +gdb_test "print A1(3)" \ + "\\(i => 2, s => \"AB\"\\)" diff --git a/gdb/testsuite/gdb.ada/dyn_stride/foo.adb b/gdb/testsuite/gdb.ada/dyn_stride/foo.adb new file mode 100644 index 0000000..7ee80b2 --- /dev/null +++ b/gdb/testsuite/gdb.ada/dyn_stride/foo.adb @@ -0,0 +1,42 @@ +-- Copyright 2015-2017 Free Software Foundation, Inc. +-- +-- This program is free software; you can redistribute it and/or modify +-- it under the terms of the GNU General Public License as published by +-- the Free Software Foundation; either version 3 of the License, or +-- (at your option) any later version. +-- +-- This program is distributed in the hope that it will be useful, +-- but WITHOUT ANY WARRANTY; without even the implied warranty of +-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +-- GNU General Public License for more details. +-- +-- You should have received a copy of the GNU General Public License +-- along with this program. If not, see . + +procedure Foo is + + procedure Nested (L, U : Integer) is + subtype Small_Type is Integer range L .. U; + type Record_Type (I : Small_Type := L) is record + S : String (1 .. I); + end record; + type Array_Type is array (Integer range <>) of Record_Type; + + A1 : Array_Type := + (1 => (I => 0, S => <>), + 2 => (I => 1, S => "A"), + 3 => (I => 2, S => "AB")); + + procedure Discard (R : Record_Type) is + begin + null; + end Discard; + + begin + Discard (A1 (1)); -- STOP + end; + +begin + Nested (0, 10); + Nested (-10, 10); +end Foo;