I forgot to include fixes for review comments I got before pushing the
previous commits (or I pushed the wrong commits). This one fixes it.
- Return {} instead of false in get_discrete_low_bound and
get_discrete_high_bound.
- Compute high bound after confirming low bound is valid in
get_discrete_bounds.
gdb/ChangeLog:
* gdbtypes.c (get_discrete_low_bound, get_discrete_high_bound):
Return {} instead of false.
(get_discrete_bounds): Compute high bound only if low bound is
valid.
Change-Id: I5f9a66b3672adfac9441068c899ab113ab2c331a
Since commit 7c6f271296 ("gdb: make get_discrete_bounds check for
non-constant range bounds"), subscripting flexible array member fails:
struct no_size
{
int n;
int items[];
};
(gdb) p *ns
$1 = {n = 3, items = 0x5555555592a4}
(gdb) p ns->items[0]
Cannot access memory at address 0xfffe555b733a0164
(gdb) p *((int *) 0x5555555592a4)
$2 = 101 <--- we would expect that
(gdb) p &ns->items[0]
$3 = (int *) 0xfffe5559ee829a24 <--- wrong address
Since the flexible array member (items) has an unspecified size, the array type
created for it in the DWARF doesn't have dimensions (this is with gcc 9.3.0,
Ubuntu 20.04):
0x000000a4: DW_TAG_array_type
DW_AT_type [DW_FORM_ref4] (0x00000038 "int")
DW_AT_sibling [DW_FORM_ref4] (0x000000b3)
0x000000ad: DW_TAG_subrange_type
DW_AT_type [DW_FORM_ref4] (0x00000031 "long unsigned int")
This causes GDB to create a range type (TYPE_CODE_RANGE) with a defined
constant low bound (dynamic_prop with kind PROP_CONST) and an undefined
high bound (dynamic_prop with kind PROP_UNDEFINED).
value_subscript gets both bounds of that range using
get_discrete_bounds. Before commit 7c6f271296, get_discrete_bounds
didn't check the kind of the dynamic_props and would just blindly read
them as if they were PROP_CONST. It would return 0 for the high bound,
because we zero-initialize the range_bounds structure. And it didn't
really matter in this case, because the returned high bound wasn't used
in the end.
Commit 7c6f271296 changed get_discrete_bounds to return a failure if
either the low or high bound is not a constant, to make sure we don't
read a dynamic prop that isn't a PROP_CONST as a PROP_CONST. This
change made get_discrete_bounds start to return a failure for that
range, and as a result would not set *lowp and *highp. And since
value_subscript doesn't check get_discrete_bounds' return value, it just
carries on an uses an uninitialized value for the low bound. If
value_subscript did check the return value of get_discrete_bounds, we
would get an error message instead of a bogus value. But it would still
be a bug, as we wouldn't be able to print the flexible array member's
elements.
Looking at value_subscript, we see that the low bound is always needed,
but the high bound is only needed if !c_style. So, change
value_subscript to use get_discrete_low_bound and
get_discrete_high_bound separately. This fixes the case described
above, where the low bound is known but the high bound isn't (and is not
needed). This restores the original behavior without accessing a
dynamic_prop in a wrong way.
A test is added. In addition to the case described above, a case with
an array member of size 0 is added, which is a GNU C extension that
existed before flexible array members were introduced. That case
currently fails when compiled with gcc <= 8. gcc <= 8 produces DWARF
similar to the one shown above, while gcc 9 adds a DW_AT_count of 0 in
there, which makes the high bound known. A case where an array member
of size 0 is the only member of the struct is also added, as that was
how PR 28675 was originally reported, and it's an interesting corner
case that I think could trigger other funny bugs.
Question about the implementation: in value_subscript, I made it such
that if the low or high bound is unknown, we fall back to zero. That
effectively makes it the same as it was before 7c6f271296. But should
we instead error() out?
gdb/ChangeLog:
PR 26875, PR 26901
* gdbtypes.c (get_discrete_low_bound): Make non-static.
(get_discrete_high_bound): Make non-static.
* gdbtypes.h (get_discrete_low_bound): New declaration.
(get_discrete_high_bound): New declaration.
* valarith.c (value_subscript): Only fetch high bound if
necessary.
gdb/testsuite/ChangeLog:
PR 26875, PR 26901
* gdb.base/flexible-array-member.c: New test.
* gdb.base/flexible-array-member.exp: New test.
Change-Id: I832056f80e6c56f621f398b4780d55a3a1e299d7
get_discrete_bounds is not flexible for ranges (TYPE_CODE_RANGE), in the
sense that it returns true (success) only if both bounds are present and
constant values.
This is a problem for code that only needs to know the low bound and
fails unnecessarily if the high bound is unknown.
Split the function in two, get_discrete_low_bound and
get_discrete_high_bound, that both return an optional. Provide a new
implementation of get_discrete_bounds based on the two others, so the
callers don't have to be changed.
gdb/ChangeLog:
* gdbtypes.c (get_discrete_bounds): Implement with
get_discrete_low_bound and get_discrete_high_bound.
(get_discrete_low_bound): New.
(get_discrete_high_bound): New.
Change-Id: I986b5e9c0dd969800e3fb9546af9c827d52e80d0
get_discrete_bounds currently has three possible return values (see its
current doc for details). It appears that for all callers, it would be
sufficient to have a boolean "worked" / "didn't work" return value.
Change the return type of get_discrete_bounds to bool and adjust all
callers. Doing so simplifies the following patch.
gdb/ChangeLog:
* gdbtypes.h (get_discrete_bounds): Return bool, adjust all
callers.
* gdbtypes.c (get_discrete_bounds): Return bool.
Change-Id: Ie51feee23c75f0cd7939742604282d745db59172
Instead of returning a boolean status and returning the value through a
pointer, return an optional that does both jobs. This helps in the
following patches, and I think it is an improvement in general.
gdb/ChangeLog:
* ada-lang.c (ada_value_slice_from_ptr): Adjust.
(ada_value_slice): Adjust.
(pos_atr): Adjust.
* gdbtypes.c (get_discrete_bounds): Adjust.
(discrete_position): Return optional.
* gdbtypes.h (discrete_position): Return optional.
Change-Id: I758dbd8858b296ee472ed39ec35db1dbd624a5ae
This fixes a long-lived bug in the s390 port.
When trying to step over a breakpoint set on a BC (branch on condition)
instruction with displaced stepping on IBM Z, gdb would incorrectly
adjust the pc regardless of whether or not the branch was taken. Since
the branch target is an absolute address, this would cause the inferior
to jump around wildly whenever the branch was taken, either crashing it
or causing it to behave unpredictably.
It turns out that the logic to handle BC instructions correctly was in
the code, but that the enum value representing its opcode has always
been incorrect.
This patch corrects the enum value to the actual opcode, fixing the
stepping problem. The enum value is also used in the prologue analysis
code, so this also fixes a minor bug where more of the prologue would
be read than was necessary.
gdb/ChangeLog:
PR breakpoints/27009
* s390-tdep.h (op_bc): Correct BC opcode value.
This is just an update in the gdb/ChangeLog to reflect a newly
created PR [27015] for a bugfix commit:
abaf3df9 arc: Write correct "eret" value during register collection
In collect_register() function of arc-linux-tdep.c, the "eret"
(exception return) register value was not being reported correctly.
This patch fixes that.
Background:
When asked for the "pc" value, we have to update the "eret" register
with GDB's STOP_PC. The "eret" instructs the kernel code where to
jump back when an instruction has stopped due to a breakpoint. This
is how collect_register() was doing so:
--------------8<--------------
if (regnum == gdbarch_pc_regnum (gdbarch))
regnum = ARC_ERET_REGNUM;
regcache->raw_collect (regnum, buf + arc_linux_core_reg_offsets[regnum]);
-------------->8--------------
Root cause:
Although this is using the correct offset (ERET register's), it is also
changing the REGNUM itself. Therefore, raw_collect (regnum, ...) is
not reading from "pc" anymore.
v2:
- Fix a copy/paste issue as rightfully addressed by Tom [1].
[1]
https://sourceware.org/pipermail/gdb-patches/2020-November/173208.html
gdb/ChangeLog:
* arc-linux-tdep.c (collect_register): Populate "eret" by
"pc" value from the regcache when asked for "pc" value.
The argument is called static_members, not static_fields.
gdb/doc/ChangeLog:
2020-11-29 Hannes Domani <ssbssa@yahoo.de>
PR python/26974
* python.texi: Fix docu for static members argument.
The locator win info is special because it is static, all the others are
created dynamically.
gdb/ChangeLog:
2020-11-29 Hannes Domani <ssbssa@yahoo.de>
PR tui/26973
* tui/tui-layout.c (tui_apply_current_layout): Don't delete the
static locator win info.
