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e5ca03b41d
With something like:
struct A { int bitfield:4; } var;
If 'var' ends up wholly-optimized out, printing 'var.bitfield' crashes
gdb here:
(top-gdb) bt
#0 0x000000000058b89f in extract_unsigned_integer (addr=0x2 <error: Cannot access memory at address 0x2>, len=2, byte_order=BFD_ENDIAN_LITTLE)
at /home/pedro/gdb/mygit/src/gdb/findvar.c:109
#1 0x00000000005a187a in unpack_bits_as_long (field_type=0x16cff70, valaddr=0x0, bitpos=16, bitsize=12) at /home/pedro/gdb/mygit/src/gdb/value.c:3347
#2 0x00000000005a1b9d in unpack_value_bitfield (dest_val=0x1b5d9d0, bitpos=16, bitsize=12, valaddr=0x0, embedded_offset=0, val=0x1b5d8d0)
at /home/pedro/gdb/mygit/src/gdb/value.c:3441
#3 0x00000000005a2a5f in value_fetch_lazy (val=0x1b5d9d0) at /home/pedro/gdb/mygit/src/gdb/value.c:3958
#4 0x00000000005a10a7 in value_primitive_field (arg1=0x1b5d8d0, offset=0, fieldno=0, arg_type=0x16d04c0) at /home/pedro/gdb/mygit/src/gdb/value.c:3161
#5 0x00000000005b01e5 in do_search_struct_field (name=0x1727c60 "bitfield", arg1=0x1b5d8d0, offset=0, type=0x16d04c0, looking_for_baseclass=0, result_ptr=0x7fffffffcaf8,
[...]
unpack_value_bitfield is already optimized-out/unavailable -aware:
(...) VALADDR points to the contents of VAL. If the VAL's contents
required to extract the bitfield from are unavailable/optimized
out, DEST_VAL is correspondingly marked unavailable/optimized out.
however, it is not considering the case of the value having no
contents buffer at all, as can happen through
allocate_optimized_out_value.
gdb/ChangeLog:
2016-08-09 Pedro Alves <palves@redhat.com>
* value.c (unpack_value_bitfield): Skip unpacking if the parent
has no contents buffer to begin with.
gdb/testsuite/ChangeLog:
2016-08-09 Pedro Alves <palves@redhat.com>
* gdb.dwarf2/bitfield-parent-optimized-out.exp: New file.
88 lines
2.2 KiB
Plaintext
88 lines
2.2 KiB
Plaintext
# Copyright 2016 Free Software Foundation, Inc.
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 3 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program. If not, see <http://www.gnu.org/licenses/>.
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# Test printing a bitfield of an optimized-out variable. Regression
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# test for PR gdb/20295.
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load_lib dwarf.exp
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# This test can only be run on targets which support DWARF-2 and use gas.
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if {![dwarf2_support]} {
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return 0
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}
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standard_testfile main.c .S
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set executable ${testfile}
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# Make some DWARF for the test.
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set asm_file [standard_output_file $srcfile2]
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Dwarf::assemble $asm_file {
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global srcdir subdir srcfile
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cu { version 3 addr_size 4 } {
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compile_unit {} {
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declare_labels struct_label var_label int_label
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int_label: base_type {
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{byte_size 4 sdata}
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{encoding @DW_ATE_signed}
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{name int}
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}
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struct_label: structure_type {
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{name S}
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{byte_size 4 DW_FORM_sdata}
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} {
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member {
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{name bitfield}
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{type :$int_label}
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{bit_size 12 DW_FORM_sdata}
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{bit_offset 20 DW_FORM_sdata}
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{data_member_location 2 DW_FORM_sdata}
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}
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member {
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{name intfield}
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{type :$int_label}
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{data_member_location 2 DW_FORM_sdata}
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}
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}
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subprogram {
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{MACRO_AT_func { main ${srcdir}/${subdir}/${srcfile} }}
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{type :$int_label}
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{external 1 flag}
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} {
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var_label: DW_TAG_variable {
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{name var}
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{location {} DW_FORM_block1}
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{type :$struct_label}
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}
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}
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}
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}
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}
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if [prepare_for_testing ${testfile}.exp $executable "${asm_file} ${srcfile}" {}] {
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return -1
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}
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if ![runto_main] {
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return -1
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}
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gdb_test "p var" " = <optimized out>"
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gdb_test "p var.bitfield" " = <optimized out>"
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gdb_test "p var.intfield" " = <optimized out>"
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