commit 65d84b76164dc8ec1a1f0f0e0fd41667065ffd4e Author: Andreas Arnez Date: Tue Jun 13 15:20:31 2017 +0200 Respect piece offset for DW_OP_bit_piece So far GDB ignores the piece offset of all kinds of DWARF bit pieces (DW_OP_bit_piece) and treats such pieces as if the offset was zero. This is fixed, and an appropriate test is added. gdb/ChangeLog: * dwarf2loc.c (read_pieced_value): Respect the piece offset, as given by DW_OP_bit_piece. (write_pieced_value): Likewise. Andreas Arnez * gdb.dwarf2/var-access.exp: Add test for composite location with nonzero piece offsets. ### a/gdb/ChangeLog ### b/gdb/ChangeLog ## -1,5 +1,11 @@ 2017-06-13 Andreas Arnez + * dwarf2loc.c (read_pieced_value): Respect the piece offset, as + given by DW_OP_bit_piece. + (write_pieced_value): Likewise. + +2017-06-13 Andreas Arnez + * dwarf2loc.c (read_pieced_value): Move the buffer allocation and some other preparations to the places where sufficient information is available. --- a/gdb/dwarf2loc.c +++ b/gdb/dwarf2loc.c @@ -1824,11 +1824,14 @@ read_pieced_value (struct value *v) int optim, unavail; if (gdbarch_byte_order (arch) == BFD_ENDIAN_BIG - && p->size < reg_bits) + && p->offset + p->size < reg_bits) { /* Big-endian, and we want less than full size. */ - source_offset_bits += reg_bits - p->size; + source_offset_bits += reg_bits - (p->offset + p->size); } + else + source_offset_bits += p->offset; + this_size = bits_to_bytes (source_offset_bits, this_size_bits); buffer.reserve (this_size); @@ -1851,6 +1854,7 @@ read_pieced_value (struct value *v) break; case DWARF_VALUE_MEMORY: + source_offset_bits += p->offset; this_size = bits_to_bytes (source_offset_bits, this_size_bits); buffer.reserve (this_size); @@ -1871,12 +1875,15 @@ read_pieced_value (struct value *v) = 8 * TYPE_LENGTH (value_type (p->v.value)); /* Use zeroes if piece reaches beyond stack value. */ - if (p->size > stack_value_size_bits) + if (p->offset + p->size > stack_value_size_bits) break; /* Piece is anchored at least significant bit end. */ if (gdbarch_byte_order (objfile_gdbarch) == BFD_ENDIAN_BIG) - source_offset_bits += stack_value_size_bits - p->size; + source_offset_bits += (stack_value_size_bits + - p->offset - p->size); + else + source_offset_bits += p->offset; copy_bitwise (contents, dest_offset_bits, value_contents_all (p->v.value), @@ -1891,6 +1898,7 @@ read_pieced_value (struct value *v) size_t n = this_size_bits; /* Cut off at the end of the implicit value. */ + source_offset_bits += p->offset; if (source_offset_bits >= literal_size_bits) break; if (n > literal_size_bits - source_offset_bits) @@ -1981,11 +1989,14 @@ write_pieced_value (struct value *to, struct value *from) ULONGEST reg_bits = 8 * register_size (arch, gdb_regnum); if (gdbarch_byte_order (arch) == BFD_ENDIAN_BIG - && p->size <= reg_bits) + && p->offset + p->size < reg_bits) { /* Big-endian, and we want less than full size. */ - dest_offset_bits += reg_bits - p->size; + dest_offset_bits += reg_bits - (p->offset + p->size); } + else + dest_offset_bits += p->offset; + this_size = bits_to_bytes (dest_offset_bits, this_size_bits); buffer.reserve (this_size); @@ -2023,6 +2034,8 @@ write_pieced_value (struct value *to, struct value *from) break; case DWARF_VALUE_MEMORY: { + dest_offset_bits += p->offset; + CORE_ADDR start_addr = p->v.mem.addr + dest_offset_bits / 8; if (dest_offset_bits % 8 == 0 && this_size_bits % 8 == 0 --- a/gdb/testsuite/gdb.dwarf2/var-access.exp +++ b/gdb/testsuite/gdb.dwarf2/var-access.exp @@ -228,6 +228,24 @@ Dwarf::assemble $asm_file { piece 1 } SPECIAL_expr} } + # One piece per bitfield, using piece offsets: 32 bits of + # an implicit value, 9 bits of a stack value, 13 bits of + # r0, and 10 bits of buf. + DW_TAG_variable { + {name "t3"} + {type :$struct_t_label} + {location { + implicit_value 0x12 0x34 0x56 0x78 0x9a + bit_piece 32 4 + const2s -280 + stack_value + bit_piece 9 2 + regx [lindex $dwarf_regnum 0] + bit_piece 13 14 + addr $buf_var + bit_piece 10 42 + } SPECIAL_expr} + } } } } @@ -304,3 +322,24 @@ gdb_test_no_output "set var t2.y = 2641" gdb_test_no_output "set var t2.z = -400" gdb_test_no_output "set var t2.x = 200" gdb_test "print t2.x + t2.y + t2.z" " = 2441" + +# Bitfield access through pieces with nonzero piece offsets. +gdb_test_no_output "set var \$[lindex $regname 0] = 0xa8000" \ + "init reg for t3.y" +gdb_test_no_output "set var *(char \[2\] *) (a + 5) = { 70, 82 }" \ + "init mem for t3.z" +switch $endian { + little {set val "u = -1484430527, x = -70, y = 42, z = 145"} + big {set val "u = 591751049, x = -70, y = 42, z = 101"} +} +gdb_test "print t3" " = \\{$val\\}" \ + "initialized t3 from reg and mem" +gdb_test_no_output "set var t3.y = -1" \ + "overwrite t3.y" +gdb_test "print/x \$[lindex $regname 0]" " = 0x7ffc000" \ + "verify t3.y through reg" +gdb_test_no_output "set var t3.z = -614" \ + "overwrite t3.z" +switch $endian {big {set val "0x59, 0xa2"} little {set val "0x6a, 0x56"}} +gdb_test "print/x *(char \[2\] *) (a + 5)" " = \\{$val\\}" \ + "verify t3.z through mem"