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[PR gdb/19893] Fix handling of synthetic C++ references

Browse Source 
https://sourceware.org/bugzilla/show_bug.cgi?id=19893

I've traced the main source of the problem to pieced_value_funcs.coerce_ref not being
implemented. Since gdb always assumes references are implemented as pointers, this
causes it to think that it's dealing with a NULL pointer, thus breaking any operations
involving synthetic references.

What I did here was implementing pieced_value_funcs.coerce_ref using some of the synthetic
pointer handling code from indirect_pieced_value, as Pedro suggested. I also made a few
adjustments to the reference printing code so that it correctly shows either the address
of the referenced value or (if it's non-addressable) the "<synthetic pointer>" string.

I also wrote some unit tests based on Dwarf::assemble; these took a while to make
because in most cases I needed a synthetic reference to a physical variable. Additionally,
I started working on a unit test for classes that have a vtable, but ran into a few issues
so that'll probably go in a future patch. One thing that should definitely be fixed is that
proc function_range (called for MACRO_AT_func) will always try to compile/link using gcc
with the default options instead of g++, thus breaking C++ compilations that require e.g. libstdc++.

gdb/ChangeLog:

	* dwarf2loc.c (coerce_pieced_ref, indirect_synthetic_pointer,
	fetch_const_value_from_synthetic_pointer): New functions.
	(indirect_pieced_value): Move lower half to indirect_synthetic_pointer.
	(pieced_value_funcs): Implement coerce_ref.
	* valops.c (value_addr): Call coerce_ref for synthetic references.
	* valprint.c (valprint_check_validity): Return true for synthetic
	references.  Also, don't show "<synthetic pointer>" if they reference
	addressable values.
	(generic_val_print_ref): Handle synthetic references.  Also move some
	code to print_ref_address.
	(print_ref_address, get_value_addr_contents): New functions.

gdb/testsuite/ChangeLog:

	* gdb.dwarf2/implref.exp: Rename to...
	* gdb.dwarf2/implref-const.exp: ...this.  Also add more test statements.
	* gdb.dwarf2/implref-array.c: New file.
	* gdb.dwarf2/implref-array.exp: Likewise.
	* gdb.dwarf2/implref-global.c: Likewise.
	* gdb.dwarf2/implref-global.exp: Likewise.
	* gdb.dwarf2/implref-struct.c: Likewise.
	* gdb.dwarf2/implref-struct.exp: Likewise.
This commit is contained in:
Martin Galvan 2016-05-31 15:54:01 -03:00
parent f7433f011e
commit 3326303bf5
12 changed files with 848 additions and 90 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
gdb/ChangeLog
View File

@ -1,3 +1,18 @@
2016-05-31 Martin Galvan <martin.galvan@tallertechnologies.com>
PR c++/19893
* dwarf2loc.c (coerce_pieced_ref, indirect_synthetic_pointer,
fetch_const_value_from_synthetic_pointer): New functions.
(indirect_pieced_value): Move lower half to indirect_synthetic_pointer.
(pieced_value_funcs): Implement coerce_ref.
* valops.c (value_addr): Call coerce_ref for synthetic references.
* valprint.c (valprint_check_validity): Return true for synthetic
references. Also, don't show "<synthetic pointer>" if they reference
addressable values.
(generic_val_print_ref): Handle synthetic references. Also move some
code to print_ref_address.
(print_ref_address, get_value_addr_contents): New functions.
2016-05-30 Jan Kratochvil <jan.kratochvil@redhat.com>
PR c++/15231

124
gdb/dwarf2loc.c
View File

@ -2061,6 +2061,66 @@ get_frame_address_in_block_wrapper (void *baton)
return get_frame_address_in_block ((struct frame_info *) baton);
}
/* Fetch a DW_AT_const_value through a synthetic pointer. */
static struct value *
fetch_const_value_from_synthetic_pointer (sect_offset die, LONGEST byte_offset,
struct dwarf2_per_cu_data *per_cu,
struct type *type)
{
struct value *result = NULL;
struct obstack temp_obstack;
struct cleanup *cleanup;
const gdb_byte *bytes;
LONGEST len;
obstack_init (&temp_obstack);
cleanup = make_cleanup_obstack_free (&temp_obstack);
bytes = dwarf2_fetch_constant_bytes (die, per_cu, &temp_obstack, &len);
if (bytes != NULL)
{
if (byte_offset >= 0
&& byte_offset + TYPE_LENGTH (TYPE_TARGET_TYPE (type)) <= len)
{
bytes += byte_offset;
result = value_from_contents (TYPE_TARGET_TYPE (type), bytes);
}
else
invalid_synthetic_pointer ();
}
else
result = allocate_optimized_out_value (TYPE_TARGET_TYPE (type));
do_cleanups (cleanup);
return result;
}
/* Fetch the value pointed to by a synthetic pointer. */
static struct value *
indirect_synthetic_pointer (sect_offset die, LONGEST byte_offset,
struct dwarf2_per_cu_data *per_cu,
struct frame_info *frame, struct type *type)
{
/* Fetch the location expression of the DIE we're pointing to. */
struct dwarf2_locexpr_baton baton
= dwarf2_fetch_die_loc_sect_off (die, per_cu,
get_frame_address_in_block_wrapper, frame);
/* If pointed-to DIE has a DW_AT_location, evaluate it and return the
resulting value. Otherwise, it may have a DW_AT_const_value instead,
or it may've been optimized out. */
if (baton.data != NULL)
return dwarf2_evaluate_loc_desc_full (TYPE_TARGET_TYPE (type), frame,
baton.data, baton.size, baton.per_cu,
byte_offset);
else
return fetch_const_value_from_synthetic_pointer (die, byte_offset, per_cu,
type);
}
/* An implementation of an lval_funcs method to indirect through a
pointer. This handles the synthetic pointer case when needed. */
@ -2115,6 +2175,7 @@ indirect_pieced_value (struct value *value)
break;
}
gdb_assert (piece != NULL);
frame = get_selected_frame (_("No frame selected."));
/* This is an offset requested by GDB, such as value subscripts.
@ -2132,43 +2193,40 @@ indirect_pieced_value (struct value *value)
TYPE_LENGTH (type), byte_order);
byte_offset += piece->v.ptr.offset;
gdb_assert (piece);
baton
= dwarf2_fetch_die_loc_sect_off (piece->v.ptr.die, c->per_cu,
get_frame_address_in_block_wrapper,
frame);
return indirect_synthetic_pointer (piece->v.ptr.die, byte_offset, c->per_cu,
frame, type);
}
if (baton.data != NULL)
return dwarf2_evaluate_loc_desc_full (TYPE_TARGET_TYPE (type), frame,
baton.data, baton.size, baton.per_cu,
byte_offset);
/* Implementation of the coerce_ref method of lval_funcs for synthetic C++
references. */
{
struct obstack temp_obstack;
struct cleanup *cleanup;
const gdb_byte *bytes;
LONGEST len;
struct value *result;
static struct value *
coerce_pieced_ref (const struct value *value)
{
struct type *type = check_typedef (value_type (value));
obstack_init (&temp_obstack);
cleanup = make_cleanup_obstack_free (&temp_obstack);
if (value_bits_synthetic_pointer (value, value_embedded_offset (value),
TARGET_CHAR_BIT * TYPE_LENGTH (type)))
{
const struct piece_closure *closure
= (struct piece_closure *) value_computed_closure (value);
struct frame_info *frame
= get_selected_frame (_("No frame selected."));
bytes = dwarf2_fetch_constant_bytes (piece->v.ptr.die, c->per_cu,
&temp_obstack, &len);
if (bytes == NULL)
result = allocate_optimized_out_value (TYPE_TARGET_TYPE (type));
else
{
if (byte_offset < 0
|| byte_offset + TYPE_LENGTH (TYPE_TARGET_TYPE (type)) > len)
invalid_synthetic_pointer ();
bytes += byte_offset;
result = value_from_contents (TYPE_TARGET_TYPE (type), bytes);
}
/* gdb represents synthetic pointers as pieced values with a single
piece. */
gdb_assert (closure != NULL);
gdb_assert (closure->n_pieces == 1);
do_cleanups (cleanup);
return result;
}
return indirect_synthetic_pointer (closure->pieces->v.ptr.die,
closure->pieces->v.ptr.offset,
closure->per_cu, frame, type);
}
else
{
/* Else: not a synthetic reference; do nothing. */
return NULL;
}
}
static void *
@ -2206,7 +2264,7 @@ static const struct lval_funcs pieced_value_funcs = {
read_pieced_value,
write_pieced_value,
indirect_pieced_value,
NULL, /* coerce_ref */
coerce_pieced_ref,
check_pieced_synthetic_pointer,
copy_pieced_value_closure,
free_pieced_value_closure

12
gdb/testsuite/ChangeLog
View File

@ -1,3 +1,15 @@
2016-05-31 Martin Galvan <martin.galvan@tallertechnologies.com>
PR c++/19893
* gdb.dwarf2/implref.exp: Rename to...
* gdb.dwarf2/implref-const.exp: ...this. Also add more test statements.
* gdb.dwarf2/implref-array.c: New file.
* gdb.dwarf2/implref-array.exp: Likewise.
* gdb.dwarf2/implref-global.c: Likewise.
* gdb.dwarf2/implref-global.exp: Likewise.
* gdb.dwarf2/implref-struct.c: Likewise.
* gdb.dwarf2/implref-struct.exp: Likewise.
2016-05-30 Antoine Tremblay <antoine.tremblay@ericsson.com>
* gdb.trace/trace-condition.exp: Add 64bit tests.

27
gdb/testsuite/gdb.dwarf2/implref-array.c Normal file
View File

@ -0,0 +1,27 @@
/* Copyright (C) 2016 Free Software Foundation, Inc.
This file is part of GDB.
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 <http://www.gnu.org/licenses/>. */
/* Test program for synthetic C++ references to arrays. */
int array[5] = {0, 1, 2, 3, 4};
int
main (void)
{
asm ("main_label: .globl main_label");
return 0;
}

171
gdb/testsuite/gdb.dwarf2/implref-array.exp Normal file
View File

@ -0,0 +1,171 @@
# Copyright 2016 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 <http://www.gnu.org/licenses/>.
# Test a C++ reference marked with DW_OP_GNU_implicit_pointer.
# The referenced value is a global array whose location is a DW_OP_addr.
if [skip_cplus_tests] {
continue
}
load_lib dwarf.exp
# This test can only be run on targets which support DWARF-2 and use gas.
if ![dwarf2_support] {
return 0
}
# We'll place the output of Dwarf::assemble in implref-array.S.
standard_testfile .c .S
# ${testfile} is now "implref-array". srcfile2 is "implref-array.S".
set executable ${testfile}
set asm_file [standard_output_file ${srcfile2}]
# We need to know the size of integer and address types in order
# to write some of the debugging info we'd like to generate.
#
# For that, we ask GDB by debugging our implref-array program.
# Any program would do, but since we already have implref-array
# specifically for this testcase, might as well use that.
if { [prepare_for_testing ${testfile}.exp ${testfile} ${srcfile}] } {
untested ${testfile}.exp
return -1
}
set array_length [get_valueof "/u" "sizeof(array) / sizeof(array\[0\])" -1]
# Create the DWARF. We need a regular variable which represents the array, and
# a reference to it that'll be marked with DW_OP_GNU_implicit_pointer.
# The variable must be global so that its name is an exported symbol that we
# can reference from the DWARF using gdb_target_symbol.
Dwarf::assemble ${asm_file} {
global srcdir subdir srcfile array_length
cu {} {
DW_TAG_compile_unit {
{DW_AT_language @DW_LANG_C_plus_plus}
} {
declare_labels int_label sizetype_label array_label variable_label ref_label
set int_size [get_sizeof "int" -1]
set upper_bound [expr ${array_length} - 1]
# gdb always assumes references are implemented as pointers.
set addr_size [get_sizeof "void *" -1]
int_label: DW_TAG_base_type {
{DW_AT_byte_size ${int_size} DW_FORM_udata}
{DW_AT_encoding @DW_ATE_signed}
{DW_AT_name "int"}
}
sizetype_label: DW_TAG_base_type {
{DW_AT_byte_size ${int_size} DW_FORM_udata}
{DW_AT_encoding @DW_ATE_unsigned}
{DW_AT_name "sizetype"}
}
array_label: DW_TAG_array_type {
{DW_AT_type :${int_label}}
} {
DW_TAG_subrange_type {
{DW_AT_type :${sizetype_label}}
{DW_AT_lower_bound 0 DW_FORM_udata}
{DW_AT_upper_bound ${upper_bound} DW_FORM_udata}
}
}
ref_label: DW_TAG_reference_type {
{DW_AT_byte_size ${addr_size} DW_FORM_udata}
{DW_AT_type :${array_label}}
}
variable_label: DW_TAG_variable {
{DW_AT_name "array"}
{DW_AT_type :${array_label}}
{DW_AT_external 1 DW_FORM_flag}
{DW_AT_location {DW_OP_addr [gdb_target_symbol "array"]} SPECIAL_expr}
}
DW_TAG_subprogram {
{MACRO_AT_func { "main" "${srcdir}/${subdir}/${srcfile}" }}
{DW_AT_type :${int_label}}
{DW_AT_external 1 DW_FORM_flag}
} {
DW_TAG_variable {
{DW_AT_name "ref"}
{DW_AT_type :${ref_label}}
{DW_AT_location {DW_OP_GNU_implicit_pointer ${variable_label} 0} SPECIAL_expr}
}
}
}
}
}
if [prepare_for_testing ${testfile}.exp ${executable} [list ${asm_file} ${srcfile}] {}] {
return -1
}
# DW_OP_GNU_implicit_pointer implementation requires a valid frame.
if ![runto_main] {
return -1
}
# This matches e.g. '(int (&)[5])'
set ref_type [format {\(int \(&\)\[%d\]\)} ${array_length}]
# This matches e.g. '(int (*)[5])'
set ptr_type [format {\(int \(\*\)\[%d\]\)} ${array_length}]
# Contents of the array. Trim leading/trailing whitespace, '{' and '}'
# since they confuse TCL to no end.
set contents [get_valueof "" "array" ""]
set contents [string trim ${contents}]
set contents [string trim ${contents} "{}"]
# Address of the referenced value.
set address [get_hexadecimal_valueof "&array" ""]
# Doing 'print ref' should show us e.g. '(int (&)[5]) 0xdeadbeef: {0, 1, 2, 3, 4}'.
gdb_test "print ref" " = ${ref_type} @${address}: \\{${contents}\\}"
# Doing 'print &ref' should show us e.g. '(int (*)[5]) 0xdeadbeef <array>'.
gdb_test "print &ref" " = ${ptr_type} ${address} <array>"
# gdb assumes C++ references are implemented as pointers, and print &(&ref)
# shows us the underlying pointer's address. Since in this case there's no
# physical pointer, gdb should tell us so.
gdb_test "print &(&ref)" "Attempt to take address of value not located in memory."
# Test assignment through the synthetic reference.
set first_value 10
gdb_test_no_output "set (ref\[0\] = ${first_value})"
# This matches '{10, 1, 2, 3, 4}'.
set new_contents [format {\{%d, 1, 2, 3, 4\}} ${first_value}]
# Doing 'print ref' should now show us e.g.
# '(int (&)[5]) <synthetic pointer>: {10, 1, 2, 3, 4}'.
gdb_test "print ref" " = ${ref_type} @${address}: ${new_contents}" "print ref after assignment"
gdb_test "print array" " = ${new_contents}" "print array after assignment"
# Test treating the array as a pointer.
set second_value 20
set new_contents [format {\{%d, %d, 2, 3, 4\}} ${first_value} ${second_value}]
gdb_test "print *ref" " = ${first_value}"
gdb_test_no_output "set (*(ref + 1) = ${second_value})"
gdb_test "print ref\[1\]" " = ${second_value}"
gdb_test "print array" " = ${new_contents}" "print array after second assignment"

53
gdb/testsuite/gdb.dwarf2/implref.exp → gdb/testsuite/gdb.dwarf2/implref-const.exp
View File

@ -13,45 +13,62 @@
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
# Test C++ references marked with DW_OP_GNU_implicit_pointer.
# Test a C++ reference marked with DW_OP_GNU_implicit_pointer.
# The referenced value is a DW_AT_const_value.
# TODO: Add more test statements after fixing bug #19893:
# https://sourceware.org/bugzilla/show_bug.cgi?id=19893.
if [skip_cplus_tests] {
continue
}
load_lib dwarf.exp
# This test can only be run on targets which support DWARF-2 and use gas.
if {![dwarf2_support]} {
if ![dwarf2_support] {
return 0
}
# We'll place the output of Dwarf::assemble in implref.S.
# We'll place the output of Dwarf::assemble in implref-const.S.
standard_testfile main.c .S
# ${testfile} is now "implref". srcfile2 is "implref.S".
# ${testfile} is now "implref-const". srcfile2 is "implref-const.S".
set executable ${testfile}
set asm_file [standard_output_file ${srcfile2}]
# We need to know the size of integer and address types in order
# to write some of the debugging info we'd like to generate.
#
# For that, we ask GDB by debugging our implref-const program.
# Any program would do, but since we already have implref-const
# specifically for this testcase, might as well use that.
if [prepare_for_testing ${testfile}.exp ${testfile} ${srcfile}] {
untested ${testfile}.exp
return -1
}
# Create the DWARF. We need a regular variable and a reference to it that'll
# be marked with DW_OP_GNU_implicit_pointer.
Dwarf::assemble $asm_file {
Dwarf::assemble ${asm_file} {
global srcdir subdir srcfile
cu { version 3 addr_size 4 } {
cu {} {
DW_TAG_compile_unit {
{DW_AT_producer "GNU C++ 4.8.4"}
{DW_AT_language @DW_LANG_C_plus_plus}
} {
declare_labels int_label const_label variable_label ref_label
set int_size [get_sizeof "int" -1]
# gdb always assumes references are implemented as pointers.
set addr_size [get_sizeof "void *" -1]
set var_value 42
int_label: DW_TAG_base_type {
{DW_AT_byte_size 4 DW_FORM_udata}
{DW_AT_byte_size ${int_size} DW_FORM_udata}
{DW_AT_encoding @DW_ATE_signed}
{DW_AT_name "int"}
}
ref_label: DW_TAG_reference_type {
{DW_AT_byte_size 4 DW_FORM_udata}
{DW_AT_byte_size ${addr_size} DW_FORM_udata}
{DW_AT_type :${int_label}}
}
@ -67,7 +84,7 @@ Dwarf::assemble $asm_file {
variable_label: DW_TAG_variable {
{DW_AT_name "var"}
{DW_AT_type :${int_label}}
{DW_AT_const_value 42 DW_FORM_udata}
{DW_AT_const_value ${var_value} DW_FORM_udata}
}
DW_TAG_variable {
@ -80,7 +97,7 @@ Dwarf::assemble $asm_file {
}
}
if [prepare_for_testing ${testfile}.exp ${executable} "${asm_file} ${srcfile}" {}] {
if [prepare_for_testing ${testfile}.exp ${executable} [list ${asm_file} ${srcfile}] {}] {
return -1
}
@ -89,10 +106,14 @@ if ![runto_main] {
return -1
}
gdb_test "print ref" " = \\(int &\\) <synthetic pointer>" "print ref"
gdb_test "print &ref" " = \\(int \\*\\) <synthetic pointer>" "print &ref"
# Doing 'print ref' should show us e.g. '(int &) <synthetic pointer>: 42'.
gdb_test "print ref" " = \\(int &\\) <synthetic pointer>: \\\d+"
# The variable isn't located in memory, thus we can't take its address.
gdb_test "print &var" "Can't take address of \"var\" which isn't an lvalue."
gdb_test "print &ref" "Attempt to take address of value not located in memory."
# gdb assumes C++ references are implemented as pointers, and print &(&ref)
# shows us the underlying pointer's address.
# Since in this case there's no physical pointer, gdb should tell us so.
gdb_test "print &\(&ref\)" "Attempt to take address of value not located in memory." "print &(&ref)"
gdb_test "print &(&ref)" "Attempt to take address of value not located in memory."

27
gdb/testsuite/gdb.dwarf2/implref-global.c Normal file
View File

@ -0,0 +1,27 @@
/* Copyright (C) 2016 Free Software Foundation, Inc.
This file is part of GDB.
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 <http://www.gnu.org/licenses/>. */
/* Test program for synthetic C++ references to global variables. */
int global_var = 42;
int
main (void)
{
asm ("main_label: .globl main_label");
return 0;
}

125
gdb/testsuite/gdb.dwarf2/implref-global.exp Normal file
View File

@ -0,0 +1,125 @@
# Copyright 2016 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 <http://www.gnu.org/licenses/>.
# Test a C++ reference marked with DW_OP_GNU_implicit_pointer.
# The referenced value is a global variable whose location is a DW_OP_addr.
if [skip_cplus_tests] {
continue
}
load_lib dwarf.exp
# This test can only be run on targets which support DWARF-2 and use gas.
if ![dwarf2_support] {
return 0
}
# We'll place the output of Dwarf::assemble in implref-global.S.
standard_testfile .c .S
# ${testfile} is now "implref-global". srcfile2 is "implref-global.S".
set executable ${testfile}
set asm_file [standard_output_file ${srcfile2}]
# We need to know the size of integer and address types in order
# to write some of the debugging info we'd like to generate.
#
# For that, we ask GDB by debugging our implref-global program.
# Any program would do, but since we already have implref-global
# specifically for this testcase, might as well use that.
if [prepare_for_testing ${testfile}.exp ${testfile} ${srcfile}] {
untested ${testfile}.exp
return -1
}
# Create the DWARF. We need a regular variable and a reference to it that'll
# be marked with DW_OP_GNU_implicit_pointer. The variable must be global so
# that its name is an exported symbol that we can reference from the DWARF
# using gdb_target_symbol.
Dwarf::assemble ${asm_file} {
global srcdir subdir srcfile
cu {} {
DW_TAG_compile_unit {
{DW_AT_language @DW_LANG_C_plus_plus}
} {
declare_labels int_label variable_label ref_label
set int_size [get_sizeof "int" -1]
# gdb always assumes references are implemented as pointers.
set addr_size [get_sizeof "void *" -1]
int_label: DW_TAG_base_type {
{DW_AT_byte_size ${int_size} DW_FORM_udata}
{DW_AT_encoding @DW_ATE_signed}
{DW_AT_name "int"}
}
ref_label: DW_TAG_reference_type {
{DW_AT_byte_size ${addr_size} DW_FORM_udata}
{DW_AT_type :${int_label}}
}
variable_label: DW_TAG_variable {
{DW_AT_name "global_var"}
{DW_AT_type :${int_label}}
{DW_AT_external 1 DW_FORM_flag}
{DW_AT_location {DW_OP_addr [gdb_target_symbol "global_var"]} SPECIAL_expr}
}
DW_TAG_subprogram {
{MACRO_AT_func { "main" "${srcdir}/${subdir}/${srcfile}" }}
{DW_AT_type :${int_label}}
{DW_AT_external 1 DW_FORM_flag}
} {
DW_TAG_variable {
{DW_AT_name "ref"}
{DW_AT_type :${ref_label}}
{DW_AT_location {DW_OP_GNU_implicit_pointer ${variable_label} 0} SPECIAL_expr}
}
}
}
}
}
if [prepare_for_testing ${testfile}.exp ${executable} [list ${asm_file} ${srcfile}] {}] {
return -1
}
# DW_OP_GNU_implicit_pointer implementation requires a valid frame.
if ![runto_main] {
return -1
}
# Address of the referenced value.
set address [get_hexadecimal_valueof "&global_var" ""]
# Doing 'print ref' should show us e.g. '(int &) @0xdeadbeef: 42'.
gdb_test "print ref" " = \\(int &\\) @${address}: \\\d+"
# Doing 'print &ref' should show us e.g. '(int *) 0xdeadbeef <global_var>'.
gdb_test "print &ref" " = \\(int \\*\\) ${address} <global_var>"
# gdb assumes C++ references are implemented as pointers, and print &(&ref)
# shows us the underlying pointer's address. Since in this case there's no
# physical pointer, gdb should tell us so.
gdb_test "print &(&ref)" "Attempt to take address of value not located in memory."
# Test assignment through the synthetic reference.
set new_value 10
gdb_test_no_output "set (ref = ${new_value})"
gdb_test "print ref" " = \\(int &\\) @${address}: ${new_value}" "print ref after assignment"
gdb_test "print global_var" " = ${new_value}" "print global_var after assignment"

43
gdb/testsuite/gdb.dwarf2/implref-struct.c Normal file
View File

@ -0,0 +1,43 @@
/* Copyright (C) 2016 Free Software Foundation, Inc.
This file is part of GDB.
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 <http://www.gnu.org/licenses/>. */
/* Test program for synthetic C++ references to structs. */
struct S {
int a;
int b;
int c;
};
struct S s1 = {
0,
1,
2
};
struct S s2 = {
10,
11,
12
};
int
main (void)
{
asm ("main_label: .globl main_label");
return 0;
}

186
gdb/testsuite/gdb.dwarf2/implref-struct.exp Normal file
View File

@ -0,0 +1,186 @@
# Copyright 2016 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 <http://www.gnu.org/licenses/>.
# Test a C++ reference marked with DW_OP_GNU_implicit_pointer.
# The referenced value is a global struct whose location is a DW_OP_addr.
if [skip_cplus_tests] {
continue
}
load_lib dwarf.exp
# This test can only be run on targets which support DWARF-2 and use gas.
if ![dwarf2_support] {
return 0
}
# We'll place the output of Dwarf::assemble in implref-struct.S.
standard_testfile .c .S
# ${testfile} is now "implref-struct". srcfile2 is "implref-struct.S".
set executable ${testfile}
set asm_file [standard_output_file ${srcfile2}]
# We need to know the size of integer and address types in order
# to write some of the debugging info we'd like to generate.
#
# For that, we ask GDB by debugging our implref-struct program.
# Any program would do, but since we already have implref-struct
# specifically for this testcase, might as well use that.
if [prepare_for_testing ${testfile}.exp ${testfile} ${srcfile} {debug c++}] {
untested ${testfile}.exp
return -1
}
# Create the DWARF. We need a regular variable for the struct and a reference
# to it that'll be marked with DW_OP_GNU_implicit_pointer. The variable must be
# global so that its name is an exported symbol that can we can reference from
# the DWARF using gdb_target_symbol.
Dwarf::assemble ${asm_file} {
global srcdir subdir srcfile
cu {} {
DW_TAG_compile_unit {
{DW_AT_language @DW_LANG_C_plus_plus}
} {
declare_labels int_label struct_label variable_label ref_label
set int_size [get_sizeof "int" -1]
# gdb always assumes references are implemented as pointers.
set addr_size [get_sizeof "void *" -1]
set S_size [get_sizeof "S" -1]
# The compiler shouldn't introduce structure padding here.
set b_offset 4
set c_offset 8
int_label: DW_TAG_base_type {
{DW_AT_byte_size ${int_size} DW_FORM_udata}
{DW_AT_encoding @DW_ATE_signed}
{DW_AT_name "int"}
}
struct_label: DW_TAG_structure_type {
{DW_AT_name "S"}
{DW_AT_byte_size ${S_size} DW_FORM_udata}
} {
DW_TAG_member {
{DW_AT_name "a"}
{DW_AT_type :${int_label}}
{DW_AT_data_member_location 0 DW_FORM_udata}
}
DW_TAG_member {
{DW_AT_name "b"}
{DW_AT_type :${int_label}}
{DW_AT_data_member_location ${b_offset} DW_FORM_udata}
}
DW_TAG_member {
{DW_AT_name "c"}
{DW_AT_type :${int_label}}
{DW_AT_data_member_location ${c_offset} DW_FORM_udata}
}
}
ref_label: DW_TAG_reference_type {
{DW_AT_byte_size ${addr_size} DW_FORM_udata}
{DW_AT_type :${struct_label}}
}
variable_label: DW_TAG_variable {
{DW_AT_name "s1"}
{DW_AT_type :${struct_label}}
{DW_AT_external 1 DW_FORM_flag}
{DW_AT_location {DW_OP_addr [gdb_target_symbol "s1"]} SPECIAL_expr}
}
DW_TAG_variable {
{DW_AT_name "s2"}
{DW_AT_type :${struct_label}}
{DW_AT_external 1 DW_FORM_flag}
{DW_AT_location {DW_OP_addr [gdb_target_symbol "s2"]} SPECIAL_expr}
}
DW_TAG_subprogram {
{MACRO_AT_func { "main" "${srcdir}/${subdir}/${srcfile}" }}
{DW_AT_type :${int_label}}
{DW_AT_external 1 DW_FORM_flag}
} {
DW_TAG_variable {
{DW_AT_name "ref"}
{DW_AT_type :${ref_label}}
{DW_AT_location {DW_OP_GNU_implicit_pointer ${variable_label} 0} SPECIAL_expr}
}
}
}
}
}
if [prepare_for_testing ${testfile}.exp ${executable} [list ${asm_file} ${srcfile}] {}] {
return -1
}
# DW_OP_GNU_implicit_pointer implementation requires a valid frame.
if ![runto_main] {
return -1
}
# Returns the struct members, e.g. '{a = 0, b = 1, c = 2}'.
proc get_members {var} {
set members [get_valueof "" ${var} ""]
# Trim leading/trailing whitespace, '{' and '}' since they confuse TCL to no end.
set members [string trim ${members}]
set members [string trim ${members} "{}"]
return ${members}
}
# Values of the struct members.
set s1_members [get_members "s1"]
set s2_members [get_members "s2"]
# Address of the referenced value.
set address [get_hexadecimal_valueof "&s1" ""]
# Test printing with both 'set print object off' and 'on', just to make sure
# the output doesn't change.
foreach_with_prefix print-object {"off" "on"} {
gdb_test_no_output "set print object ${print-object}"
# Doing 'print ref' should show us e.g.
# '(S &) @0xdeadbeef: {a = 0, b = 1, c = 2}'.
gdb_test "print ref" " = \\(S &\\) @${address}: \\{${s1_members}\\}"
# Doing 'print &ref' should show us e.g. '(S *) 0xdeadbeef <s1>'.
gdb_test "print &ref" " = \\(S \\*\\) ${address} <s1>"
# gdb assumes C++ references are implemented as pointers, and
# print &(&ref) shows us the underlying pointer's address.
# Since in this case there's no physical pointer, gdb should tell us so.
gdb_test "print &(&ref)" "Attempt to take address of value not located in memory."
}
# Test assignment through the synthetic reference.
gdb_test_no_output "set (ref = s2)"
foreach_with_prefix print-object {"off" "on"} {
gdb_test_no_output "set print object ${print-object}"
gdb_test "print ref" " = \\(S &\\) @${address}: \\{${s2_members}\\}" "print ref after assignment"
gdb_test "print s1" " = \\{${s2_members}\\}" "print s1 after assignment"
}

34
gdb/valops.c
View File

@ -1465,22 +1465,28 @@ value_addr (struct value *arg1)
if (TYPE_CODE (type) == TYPE_CODE_REF)
{
/* Copy the value, but change the type from (T&) to (T*). We
keep the same location information, which is efficient, and
allows &(&X) to get the location containing the reference.
Do the same to its enclosing type for consistency. */
struct type *type_ptr
= lookup_pointer_type (TYPE_TARGET_TYPE (type));
struct type *enclosing_type
= check_typedef (value_enclosing_type (arg1));
struct type *enclosing_type_ptr
= lookup_pointer_type (TYPE_TARGET_TYPE (enclosing_type));
if (value_bits_synthetic_pointer (arg1, value_embedded_offset (arg1),
TARGET_CHAR_BIT * TYPE_LENGTH (type)))
arg1 = coerce_ref (arg1);
else
{
/* Copy the value, but change the type from (T&) to (T*). We
keep the same location information, which is efficient, and
allows &(&X) to get the location containing the reference.
Do the same to its enclosing type for consistency. */
struct type *type_ptr
= lookup_pointer_type (TYPE_TARGET_TYPE (type));
struct type *enclosing_type
= check_typedef (value_enclosing_type (arg1));
struct type *enclosing_type_ptr
= lookup_pointer_type (TYPE_TARGET_TYPE (enclosing_type));
arg2 = value_copy (arg1);
deprecated_set_value_type (arg2, type_ptr);
set_value_enclosing_type (arg2, enclosing_type_ptr);
arg2 = value_copy (arg1);
deprecated_set_value_type (arg2, type_ptr);
set_value_enclosing_type (arg2, enclosing_type_ptr);
return arg2;
return arg2;
}
}
if (TYPE_CODE (type) == TYPE_CODE_FUNC)
return value_coerce_function (arg1);

121
gdb/valprint.c
View File

@ -335,8 +335,22 @@ valprint_check_validity (struct ui_file *stream,
if (value_bits_synthetic_pointer (val, TARGET_CHAR_BIT * embedded_offset,
TARGET_CHAR_BIT * TYPE_LENGTH (type)))
{
fputs_filtered (_("<synthetic pointer>"), stream);
return 0;
const int is_ref = TYPE_CODE (type) == TYPE_CODE_REF;
int ref_is_addressable = 0;
if (is_ref)
{
const struct value *deref_val = coerce_ref_if_computed (val);
if (deref_val != NULL)
ref_is_addressable = value_lval_const (deref_val) == lval_memory;
}
if (!is_ref || !ref_is_addressable)
fputs_filtered (_("<synthetic pointer>"), stream);
/* C++ references should be valid even if they're synthetic. */
return is_ref;
}
if (!value_bytes_available (val, embedded_offset, TYPE_LENGTH (type)))
@ -484,6 +498,42 @@ generic_val_print_memberptr (struct type *type, const gdb_byte *valaddr,
original_value, options, 0, stream);
}
/* Print '@' followed by the address contained in ADDRESS_BUFFER. */
static void
print_ref_address (struct type *type, const gdb_byte *address_buffer,
int embedded_offset, struct ui_file *stream)
{
struct gdbarch *gdbarch = get_type_arch (type);
if (address_buffer != NULL)
{
CORE_ADDR address
= extract_typed_address (address_buffer + embedded_offset, type);
fprintf_filtered (stream, "@");
fputs_filtered (paddress (gdbarch, address), stream);
}
/* Else: we have a non-addressable value, such as a DW_AT_const_value. */
}
/* If VAL is addressable, return the value contents buffer of a value that
represents a pointer to VAL. Otherwise return NULL. */
static const gdb_byte *
get_value_addr_contents (struct value *deref_val)
{
gdb_assert (deref_val != NULL);
if (value_lval_const (deref_val) == lval_memory)
return value_contents_for_printing_const (value_addr (deref_val));
else
{
/* We have a non-addressable value, such as a DW_AT_const_value. */
return NULL;
}
}
/* generic_val_print helper for TYPE_CODE_REF. */
static void
@ -492,41 +542,58 @@ generic_val_print_ref (struct type *type, const gdb_byte *valaddr,
const struct value *original_value,
const struct value_print_options *options)
{
struct gdbarch *gdbarch = get_type_arch (type);
struct type *elttype = check_typedef (TYPE_TARGET_TYPE (type));
struct value *deref_val = NULL;
const int value_is_synthetic
= value_bits_synthetic_pointer (original_value,
TARGET_CHAR_BIT * embedded_offset,
TARGET_CHAR_BIT * TYPE_LENGTH (type));
const int must_coerce_ref = ((options->addressprint && value_is_synthetic)
|| options->deref_ref);
const int type_is_defined = TYPE_CODE (elttype) != TYPE_CODE_UNDEF;
if (must_coerce_ref && type_is_defined)
{
deref_val = coerce_ref_if_computed (original_value);
if (deref_val != NULL)
{
/* More complicated computed references are not supported. */
gdb_assert (embedded_offset == 0);
}
else
deref_val = value_at (TYPE_TARGET_TYPE (type),
unpack_pointer (type, valaddr + embedded_offset));
}
/* Else, original_value isn't a synthetic reference or we don't have to print
the reference's contents.
Notice that for references to TYPE_CODE_STRUCT, 'set print object on' will
cause original_value to be a not_lval instead of an lval_computed,
which will make value_bits_synthetic_pointer return false.
This happens because if options->objectprint is true, c_value_print will
overwrite original_value's contents with the result of coercing
the reference through value_addr, and then set its type back to
TYPE_CODE_REF. In that case we don't have to coerce the reference again;
we can simply treat it as non-synthetic and move on. */
if (options->addressprint)
{
CORE_ADDR addr
= extract_typed_address (valaddr + embedded_offset, type);
const gdb_byte *address = (value_is_synthetic && type_is_defined
? get_value_addr_contents (deref_val)
: valaddr);
print_ref_address (type, address, embedded_offset, stream);
fprintf_filtered (stream, "@");
fputs_filtered (paddress (gdbarch, addr), stream);
if (options->deref_ref)
fputs_filtered (": ", stream);
}
/* De-reference the reference. */
if (options->deref_ref)
{
if (TYPE_CODE (elttype) != TYPE_CODE_UNDEF)
{
struct value *deref_val;
deref_val = coerce_ref_if_computed (original_value);
if (deref_val != NULL)
{
/* More complicated computed references are not supported. */
gdb_assert (embedded_offset == 0);
}
else
deref_val = value_at (TYPE_TARGET_TYPE (type),
unpack_pointer (type,
(valaddr
+ embedded_offset)));
common_val_print (deref_val, stream, recurse, options,
current_language);
}
if (type_is_defined)
common_val_print (deref_val, stream, recurse, options,
current_language);
else
fputs_filtered ("???", stream);
}