From 2a62dfa93f1980fd8d5b0651753c550942fa30b6 Mon Sep 17 00:00:00 2001 From: Joel Brobecker Date: Sat, 8 Sep 2018 16:44:36 -0500 Subject: (Ada) assigning packed array aggregate with variable as component Consider a variable "PRA" defined as a packed array of packed records as follow: subtype Int is Integer range 0 .. 7; type Packed_Rec is record X, Y : Int; W : Integer; end record; pragma Pack (Packed_Rec); type Packed_RecArr is array (Integer range <>) of Packed_Rec; pragma Pack (Packed_RecArr); PRA : Packed_RecArr (1 .. 3); Consider also a variable "PR", which is a Packed_Rec record, declared as follow: PR : Packed_Rec := (2, 2, 2); Trying to assign a new value to PRA using an aggregate expression where one of the components is our variable PR yields the wrong result on big-endian machines (e.g. on ppc-linux): (gdb) p pra := (pr, (2,2,2), (2,2,2)) $6 = ((x => 1, y => 0, w => 8), [...] On the other hand, replacing "pr" by "(2,2,2)" does work. I tracked the issue down to the bit offset we use to extract the value of "PR" and copy it inside PRA. in value_assign_to_component, we have: if (gdbarch_bits_big_endian (get_type_arch (value_type (container)))) move_bits ([target buffer], [bit offset in target buffer], [source buffer where PR is stored], TYPE_LENGTH (value_type (component)) * TARGET_CHAR_BIT - bits, bits, 1); The issue is with the third-to-last argument, which provides the bit offset where the value of PR is stored relative to its start address, and therefore the bit offset relative to the start of the source buffer passed as the previous argument. In our case, component is a 38bit packed record whose TYPE_LENGTH is 5 bytes, so the bit-offset that gets calculated is 2 (bits). However, that formula only really applies to scalars, whereas in our case, we have a record (struct). The offset in the non-scalar case should be zero. gdb/ChangeLog: * ada-lang.c (value_assign_to_component): In the case of big-endian targets, extract the bits of the given VAL using an src_offset of zero if container is not a scalar. gdb/testsuite/ChangeLog: * gdb.ada/packed_array_assign: New testcase. --- gdb/ada-lang.c | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-) (limited to 'gdb/ada-lang.c') diff --git a/gdb/ada-lang.c b/gdb/ada-lang.c index ef87164..3618e1d 100644 --- a/gdb/ada-lang.c +++ b/gdb/ada-lang.c @@ -2809,11 +2809,18 @@ value_assign_to_component (struct value *container, struct value *component, bits = value_bitsize (component); if (gdbarch_bits_big_endian (get_type_arch (value_type (container)))) - move_bits (value_contents_writeable (container) + offset_in_container, - value_bitpos (container) + bit_offset_in_container, - value_contents (val), - TYPE_LENGTH (value_type (component)) * TARGET_CHAR_BIT - bits, - bits, 1); + { + int src_offset; + + if (is_scalar_type (check_typedef (value_type (component)))) + src_offset + = TYPE_LENGTH (value_type (component)) * TARGET_CHAR_BIT - bits; + else + src_offset = 0; + move_bits (value_contents_writeable (container) + offset_in_container, + value_bitpos (container) + bit_offset_in_container, + value_contents (val), src_offset, bits, 1); + } else move_bits (value_contents_writeable (container) + offset_in_container, value_bitpos (container) + bit_offset_in_container, -- cgit v1.1