diff options
| author | Pedro Alves <palves@redhat.com> | 2016-08-09 12:04:48 +0100 |
|---|---|---|
| committer | Pedro Alves <palves@redhat.com> | 2016-08-09 12:04:48 +0100 |
| commit | e5ca03b41d2c94919d5cb59d8d7adad98c29d156 (patch) | |
| tree | 910d3597a5ec740a7a6f7eef31cc42198553036d /gdb/value.c | |
| parent | 02183cb7d306469dc7cf57f39c97bf3e98829585 (diff) | |
Fix PR gdb/20295: GDB segfaults printing bitfield member of optimized out value
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.
Diffstat (limited to 'gdb/value.c')
| -rw-r--r-- | gdb/value.c | 23 |
1 files changed, 15 insertions, 8 deletions
diff --git a/gdb/value.c b/gdb/value.c index cd59f43f01..d6eab24e62 100644 --- a/gdb/value.c +++ b/gdb/value.c @@ -3430,17 +3430,24 @@ unpack_value_bitfield (struct value *dest_val, enum bfd_endian byte_order; int src_bit_offset; int dst_bit_offset; - LONGEST num; struct type *field_type = value_type (dest_val); - /* First, unpack and sign extend the bitfield as if it was wholly - available. Invalid/unavailable bits are read as zero, but that's - OK, as they'll end up marked below. */ byte_order = gdbarch_byte_order (get_type_arch (field_type)); - num = unpack_bits_as_long (field_type, valaddr + embedded_offset, - bitpos, bitsize); - store_signed_integer (value_contents_raw (dest_val), - TYPE_LENGTH (field_type), byte_order, num); + + /* First, unpack and sign extend the bitfield as if it was wholly + valid. Optimized out/unavailable bits are read as zero, but + that's OK, as they'll end up marked below. If the VAL is + wholly-invalid we may have skipped allocating its contents, + though. See allocate_optimized_out_value. */ + if (valaddr != NULL) + { + LONGEST num; + + num = unpack_bits_as_long (field_type, valaddr + embedded_offset, + bitpos, bitsize); + store_signed_integer (value_contents_raw (dest_val), + TYPE_LENGTH (field_type), byte_order, num); + } /* Now copy the optimized out / unavailability ranges to the right bits. */ |