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This changes gdb to use scalar arithmetic for expression evaluation.
I suspect this patch is not truly complete, as there may be code paths
that still don't correctly handle 128-bit integers. However, many
things do work now.
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30190
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Both value_equal and value_less use value_as_long to check a
presumably boolean result of calling value_binop. However,
value_binop in this case actually returns an int as wide as its
arguments, and this approach can then fail for integers wider than
LONGEST. Instead, rewrite this in a form that works for any size
integer.
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This adds some operators and methods to gdb_mpq, in preparation for
making its implementation private.
This only adds the operators currently needed by gdb. More could be
added as necessary.
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scalar_binop has code for "&&" and "||", but I think this code can't
currently be run -- and, furthermore, it doesn't make sense to have
this code here, as the point of these operators is to short-circuit
evaluation.
This patch removes the dead code.
Regression tested on x86-64 Fedora 36.
Approved-by: Kevin Buettner <kevinb@redhat.com>
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I noticed a very stale comment in valarith.c. This patch fixes a few
comments in this area.
Reviewed-By: Andrew Burgess <aburgess@redhat.com>
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check_valid_shift_count has an 'int' parameter that really should be
an enum exp_opcode. This patch makes the change. Tested by
rebuilding.
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value_in is unused. From git log, it seems to have been part of the
Chill language, which was removed from gdb eons ago. This patch
removes the function. Tested by rebuilding.
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A while back I discovered that this does not issue an error:
(gdb) p $x = (void * ) 57
$3 = (void *) 0x39
(gdb) p $x + 7 = 3
$6 = (void *) 0x3
This patch fixes the bug.
Regression tested on x86-64 Fedora 36.
Reviewed-By: Bruno Larsen <blarsen@redhat.com>
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=19312
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This removes deprecated_lval_hack and the VALUE_LVAL macro, replacing
all uses with a call to value::lval.
Approved-By: Simon Marchi <simon.marchi@efficios.com>
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This introduces the set_lval method on value, one step toward removing
deprecated_lval_hack. Ultimately I think the goal should be for some
of these set_* methods to be replaced with constructors; but I haven't
done this, as the series is already too long. Other 'deprecated'
methods can probably be handled the same way.
Approved-By: Simon Marchi <simon.marchi@efficios.com>
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This turns value_from_xmethod, result_type_of_xmethod, and
call_xmethod to be methods of value. value_from_xmethod is a static
"constructor" now.
Approved-By: Simon Marchi <simon.marchi@efficios.com>
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This turns set_value_component_location into a method of value.
Approved-By: Simon Marchi <simon.marchi@efficios.com>
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This turns many functions that are related to optimized-out or
availability-checking to be methods of value. The static function
value_entirely_covered_by_range_vector is also converted to be a
private method.
Approved-By: Simon Marchi <simon.marchi@efficios.com>
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This turns the remaining value_contents functions -- value_contents,
value_contents_all, value_contents_for_printing, and
value_contents_for_printing_const -- into methods of value. It also
converts the static functions require_not_optimized_out and
require_available to be private methods.
Approved-By: Simon Marchi <simon.marchi@efficios.com>
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This turns value_contents_raw, value_contents_writeable, and
value_contents_all_raw into methods on value. The remaining functions
will be changed later in the series; they were a bit trickier and so I
didn't include them in this patch.
Approved-By: Simon Marchi <simon.marchi@efficios.com>
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This turns value_zero into a static "constructor" of value.
Approved-By: Simon Marchi <simon.marchi@efficios.com>
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This changes allocate_value to be a static "constructor" of value.
Approved-By: Simon Marchi <simon.marchi@efficios.com>
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This changes the value_address and set_value_address functions to be
methods of value.
Approved-By: Simon Marchi <simon.marchi@efficios.com>
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This changes the value_lazy and set_value_lazy functions to be methods
of value. Much of this patch was written by script.
Approved-By: Simon Marchi <simon.marchi@efficios.com>
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This changes value_type to be a method of value. Much of this patch
was written by script.
Approved-By: Simon Marchi <simon.marchi@efficios.com>
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While it makes sense to allow accessing out-of-bounds elements in the
debuggee and see whatever there might happen to be there in memory (we
are a debugger and not a programming rules enforcement facility and we
want to make people's life easier in chasing bugs), e.g.:
(gdb) print one_hundred[-1]
$1 = 0
(gdb) print one_hundred[100]
$2 = 0
(gdb)
we shouldn't really pretend that we have any meaningful data around
values recorded in history (what these commands really retrieve are
current debuggee memory contents outside the original data accessed,
really confusing in my opinion). Mark values recorded in history as
such then and verify accesses to be in-range for them:
(gdb) print one_hundred[-1]
$1 = <unavailable>
(gdb) print one_hundred[100]
$2 = <unavailable>
Add a suitable test case, which also covers integer overflows in data
location calculation.
Approved-By: Tom Tromey <tom@tromey.com>
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This commit is the result of running the gdb/copyright.py script,
which automated the update of the copyright year range for all
source files managed by the GDB project to be updated to include
year 2023.
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I looked at all the spots using value_mark, and converted all the
straightforward ones to use scoped_value_mark instead.
Regression tested on x86-64 Fedora 34.
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Remove the macro, replace all uses with calls to type::length.
Change-Id: Ib9bdc954576860b21190886534c99103d6a47afb
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Remove the macro, replace all uses by calls to type::target_type.
Change-Id: Ie51d3e1e22f94130176d6abd723255282bb6d1ed
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When building gdb with -fsanitize=undefined, I run into:
...
$ gdb -q -batch -ex "p -(-0x7fffffffffffffff - 1)"
src/gdb/valarith.c:1385:10: runtime error: signed integer overflow: \
0 - -9223372036854775808 cannot be represented in type 'long int'
$1 = -9223372036854775808
...
Fix this by performing the substraction in scalar_binop using unsigned types.
Tested on x86_64-linux.
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I noticed that a build of GDB with GCC + --enable-ubsan, testing
against GDBserver showed this GDB crash:
(gdb) PASS: gdb.trace/trace-condition.exp: trace: 0x00abababcdcdcdcd << 46 == 0x7373400000000000: advance to trace begin
tstart
../../src/gdb/valarith.c:1365:15: runtime error: left shift of 48320975398096333 by 46 places cannot be represented in type 'long int'
ERROR: GDB process no longer exists
GDB process exited with wait status 269549 exp9 0 1
UNRESOLVED: gdb.trace/trace-condition.exp: trace: 0x00abababcdcdcdcd << 46 == 0x7373400000000000: start trace experiment
The problem is that, "0x00abababcdcdcdcd << 46" is an undefined signed
left shift, because the result is not representable in the type of the
lhs, which is signed. This actually became defined in C++20, and if
you compile with "g++ -std=c++20 -Wall", you'll see that GCC no longer
warns about it, while it warns if you specify prior language versions.
While at it, there are a couple other situations that are undefined
(and are still undefined in C++20) and result in GDB dying: shifting
by a negative ammount, or by >= than the bit size of the promoted lhs.
For the latter, GDB shifts using (U)LONGEST internally, so you have to
shift by >= 64 bits to see it:
$ gdb --batch -q -ex "p 1 << -1"
../../src/gdb/valarith.c:1365:15: runtime error: shift exponent -1 is negative
$ # gdb exited
$ gdb --batch -q -ex "p 1 << 64"
../../src/gdb/valarith.c:1365:15: runtime error: shift exponent 64 is too large for 64-bit type 'long int'
$ # gdb exited
Also, right shifting a negative value is implementation-defined
(before C++20, after which it is defined). For this, I chose to
change nothing in GDB other than adding tests, as I don't really know
whether we need to do anything. AFAIK, most implementations do an
arithmetic right shift, and it may be we don't support any host or
target that behaves differently. Plus, this becomes defined in C++20
exactly as arithmetic right shift.
Compilers don't error out on such shifts, at best they warn, so I
think GDB should just continue doing the shifts anyhow too.
Thus:
- Adjust scalar_binop to avoid the undefined paths, either by adding
explicit result paths, or by casting the lhs of the left shift to
unsigned, as appropriate.
For the shifts by a too-large count, I made the result be what you'd
get if you split the large count in a series of smaller shifts.
Thus:
Left shift, positive or negative lhs:
V << 64
=> V << 16 << 16 << 16 << 16
=> 0
Right shift, positive lhs:
Vpos >> 64
=> Vpos >> 16 >> 16 >> 16 >> 16
=> 0
Right shift, negative lhs:
Vneg >> 64
=> Vneg >> 16 >> 16 >> 16 >> 16
=> -1
This is actually Go's semantics (the compiler really emits
instructions to make it so that you get 0 or -1 if you have a
too-large shift). So for that language GDB does the shift and
nothing else. For other C-like languages where such a shift is
undefined, GDB warns in addition to performing the shift.
For shift by a negative count, for Go, this is a hard error. For
other languages, since their compilers only warn, I made GDB warn
too. The semantics I chose (we're free to pick them since this is
undefined behavior) is as-if you had shifted by the count cast to
unsigned, thus as if you had shifted by a too-large count, thus the
same as the previous scenario illustrated above.
Examples:
(gdb) set language go
(gdb) p 1 << 100
$1 = 0
(gdb) p -1 << 100
$2 = 0
(gdb) p 1 >> 100
$3 = 0
(gdb) p -1 >> 100
$4 = -1
(gdb) p -2 >> 100
$5 = -1
(gdb) p 1 << -1
left shift count is negative
(gdb) set language c
(gdb) p -2 >> 100
warning: right shift count >= width of type
$6 = -1
(gdb) p -2 << 100
warning: left shift count >= width of type
$7 = 0
(gdb) p 1 << -1
warning: left shift count is negative
$8 = 0
(gdb) p -1 >> -1
warning: right shift count is negative
$9 = -1
- The warnings' texts are the same as what GCC prints.
- Add comprehensive tests in a new gdb.base/bitshift.exp testcase, so
that we exercise all these scenarios.
Change-Id: I8bcd5fa02de3114b7ababc03e65702d86ec8d45d
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This started as a patch to implement string concatenation for Ada.
However, while working on this, I looked at how this code could
possibly be called. It turns out there are only two users of
concat_operation: Ada and D. So, in addition to implementing this for
Ada, this patch rewrites value_concat, removing the odd "concatenate
or repeat" semantics, which were completely unused. As Ada and D both
seem to represent strings using TYPE_CODE_ARRAY, this removes the
TYPE_CODE_STRING code from there as well.
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eval_op_concat has code to search for an operator overload of
BINOP_CONCAT. However, the operator overloading code is specific to
C++, which does not have this operator. And,
binop_types_user_defined_p rejects this case right at the start, and
value_x_binop does not handle this case. I think this code has been
dead for a very long time. This patch removes it and hoists the
remaining call into concatenation::evaluate, removing eval_op_concat
entirely.
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This commit brings all the changes made by running gdb/copyright.py
as per GDB's Start of New Year Procedure.
For the avoidance of doubt, all changes in this commits were
performed by the script.
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While working on a Python script, which was interacting with a remote
target, I noticed some weird slowness in GDB. In my program I had a
structure something like this:
struct foo_t
{
int array[5];
};
struct foo_t global_foo;
Then in the Python script I was fetching a complete copy of global
foo, like:
val = gdb.parse_and_eval('global_foo')
val.fetch_lazy()
Then I would work with items in foo_t.array, like:
print(val['array'][1])
I called the fetch_lazy method specifically because I knew I was going
to end up accessing almost all of the contents of val, and so I wanted
GDB to do a single remote protocol call to fetch all the contents in
one go, rather than trying to do lazy fetches for a couple of bytes at
a time.
What I observed was that, after the fetch_lazy call, GDB does,
correctly, fetch the entire contents of global_foo, including all of
the contents of array, however, when I access val.array[1], GDB still
goes and fetches the value of this element from the remote target.
What's going on is that in valarith.c, in value_subscript, for C like
languages, we always end up treating the array value as a pointer, and
then doing value_ptradd, and value_ind, the second of these calls
always returns a lazy value.
My guess is that this approach allows us to handle indexing off the
end of an array, when working with zero element arrays, or when
indexing a raw pointer as an array. And, I agree, that in these
cases, where, even when the original value is non-lazy, we still will
not have the content of the array loaded, we should be using the
value_ind approach.
However, for cases where we do have the array contents loaded, and we
do know the bounds of the array, I think we should be using
value_subscripted_rvalue, which is what we use for non C like
languages.
One problem I did run into, exposed by gdb.base/charset.exp, was that
value_subscripted_rvalue stripped typedefs from the element type of
the array, which means the value returned will not have the same type
as an element of the array, but would be the raw, non-typedefed,
type. In charset.exp we got back an 'int' instead of a
'wchar_t' (which is a typedef of 'int'), and this impacts how we print
the value. Removing typedefs from the resulting value just seems
wrong, so I got rid of that, and I don't see any test regressions.
With this change in place, my original Python script is now doing no
additional memory accesses, and its performance increases about 10x!
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Change a few relatively obvious spots using value contents to propagate
the use array_view a bit more.
Change-Id: I5338a60986f06d5969fec803d04f8423c9288a15
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An assertion was recently added to array_view::operator[] to ensure we
don't do out of bounds accesses. However, when the array_view is copied
to or from using memcpy, it bypasses that safety.
To address this, add a `copy` free function that copies data from an
array view to another, ensuring that the destination and source array
views have the same size. When copying to or from parts of an
array_view, we are expected to use gdb::array_view::slice, which does
its own bounds check. With all that, any copy operation that goes out
of bounds should be caught by an assertion at runtime.
copy is implemented using std::copy and std::copy_backward, which, at
least on libstdc++, appears to pick memmove when copying trivial data.
So in the end there shouldn't be much difference vs using a bare memcpy,
as we do right now. When copying non-trivial data, std::copy and
std::copy_backward assigns each element in a loop.
To properly support overlapping ranges, we must use std::copy or
std::copy_backward, depending on whether the destination is before the
source or vice-versa. std::copy and std::copy_backward don't support
copying exactly overlapping ranges (where the source range is equal to
the destination range). But in this case, no copy is needed anyway, so
we do nothing.
The order of parameters of the new copy function is based on std::copy
and std::copy_backward, where the source comes before the destination.
Change a few randomly selected spots to use the new function, to show
how it can be used.
Add a test for the new function, testing both with arrays of a trivial
type (int) and of a non-trivial type (foo). Test non-overlapping
ranges as well as three kinds of overlapping ranges: source before dest,
dest before source, and dest == source.
Change-Id: Ibeaca04e0028410fd44ce82f72e60058d6230a03
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The function value_subscripted_rvalue is only used in valarith.c, so
lets make it a static function.
There should be no user visible change after this commit.
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The bug fixed by this [1] patch was caused by an out-of-bounds access to
a value's content. The code gets the value's content (just a pointer)
and then indexes it with a non-sensical index.
This made me think of changing functions that return value contents to
return array_views instead of a plain pointer. This has the advantage
that when GDB is built with _GLIBCXX_DEBUG, accesses to the array_view
are checked, making bugs more apparent / easier to find.
This patch changes the return types of these functions, and updates
callers to call .data() on the result, meaning it's not changing
anything in practice. Additional work will be needed (which can be done
little by little) to make callers propagate the use of array_view and
reap the benefits.
[1] https://sourceware.org/pipermail/gdb-patches/2021-September/182306.html
Change-Id: I5151f888f169e1c36abe2cbc57620110673816f3
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I noticed that value_true is declared in language.h and defined in
language.c. However, as part of the value API, I think it would be
better in one of those files. And, because it is very short, I
changed it to be an inline function in value.h. I've also removed a
comment from the implementation, on the basis that it seems obsolete
-- if the change it suggests was needed, it probably would have been
done by now; and if it is needed in the future, odds are it would be
done differently anyway.
Finally, this patch also changes value_true and value_logical_not to
return a bool, and updates some uses.
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Following on from the previous commit, this commit changes the API of
value_struct_elt to take gdb::optional<gdb::array_view<value *>>
instead of a pointer to the gdb::array_view.
This makes the optional nature of the array_view parameter explicit.
This commit is purely a refactoring commit, there should be no user
visible change after this commit.
I have deliberately kept this refactor separate from the previous two
commits as this is a more extensive change, and I'm not 100% sure that
using gdb::optional for the parameter type, instead of a pointer, is
going to be to everyone's taste. If there's push back on this patch
then this one can be dropped from the series.
gdb/ChangeLog:
* ada-lang.c (desc_bounds): Use '{}' instead of NULL to indicate
an empty gdb::optional when calling value_struct_elt.
(desc_data): Likewise.
(desc_one_bound): Likewise.
* eval.c (structop_base_operation::evaluate_funcall): Pass
gdb::array_view, not a gdb::array_view* to value_struct_elt.
(eval_op_structop_struct): Use '{}' instead of NULL to indicate
an empty gdb::optional when calling value_struct_elt.
(eval_op_structop_ptr): Likewise.
* f-lang.c (fortran_structop_operation::evaluate): Likewise.
* guile/scm-value.c (gdbscm_value_field): Likewise.
* m2-lang.c (eval_op_m2_high): Likewise.
(eval_op_m2_subscript): Likewise.
* opencl-lang.c (opencl_structop_operation::evaluate): Likewise.
* python/py-value.c (valpy_getitem): Likewise.
* rust-lang.c (rust_val_print_str): Likewise.
(rust_range): Likewise.
(rust_subscript): Likewise.
(eval_op_rust_structop): Likewise.
(rust_aggregate_operation::evaluate): Likewise.
* valarith.c (value_user_defined_op): Likewise.
* valops.c (search_struct_method): Change parameter type, update
function body accordingly, and update header comment.
(value_struct_elt): Change parameter type, update function body
accordingly.
* value.h (value_struct_elt): Update declaration.
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After the previous commit, this commit updates the value_struct_elt
function to take an array_view rather than a NULL terminated array of
values.
The requirement for a NULL terminated array of values actually stems
from typecmp, so the change from an array to array_view needs to be
propagated through to this function.
While making this change I noticed that this fixes another bug, in
value_x_binop and value_x_unop GDB creates an array of values which
doesn't have a NULL at the end. An array_view of this array is passed
to value_user_defined_op, which then unpacks the array_view and passed
the raw array to value_struct_elt, but only if the language is not
C++.
As value_x_binop and value_x_unop can only request member functions
with the names of C++ operators, then most of the time, assuming the
inferior is not a C++ program, then GDB will not find a matching
member function with the call to value_struct_elt, and so typecmp will
never be called, and so, GDB will avoid undefined behaviour.
However, it is worth remembering that, when GDB's language is set to
"auto", the current language is selected based on the language of the
current compilation unit. As C++ programs usually link against libc,
which is written in C, then, if the inferior is stopped in libc GDB
will set the language to C. And so, it is possible that we will end
up using value_struct_elt to try and lookup, and match, a C++
operator. If this occurs then GDB will experience undefined
behaviour.
I have extended the test added in the previous commit to also cover
this case.
Finally, this commit changes the API from passing around a pointer to
an array to passing around a pointer to an array_view. The reason for
this is that we need to be able to distinguish between the cases where
we call value_struct_elt with no arguments, i.e. we are looking up a
struct member, but we either don't have the arguments we want to pass
yet, or we don't expect there to be any need for GDB to use the
argument types to resolve any overloading; and the second case where
we call value_struct_elt looking for a function that takes no
arguments, that is, the argument list is empty.
NOTE: While writing this I realise that if we pass an array_view at
all then it will always have at least one item in it, the `this'
pointer for the object we are planning to call the method on. So we
could, I guess, pass an empty array_view to indicate the case where we
don't know anything about the arguments, and when the array_view is
length 1 or more, it means we do have the arguments. However, though
we could do this, I don't think this would be better, the length 0 vs
length 1 difference seems a little too subtle, I think that there's a
better solution...
I think a better solution would be to wrap the array_view in a
gdb::optional, this would make the whole, do we have an array view or
not question explicit.
I haven't done this as part of this commit as making that change is
much more extensive, every user of value_struct_elt will need to be
updated, and as this commit already contains a bug fix, I wanted to
keep the large refactoring in a separate commit, so, check out the
next commit for the use of gdb::optional.
gdb/ChangeLog:
PR gdb/27994
* eval.c (structop_base_operation::evaluate_funcall): Pass
array_view instead of array to value_struct_elt.
* valarith.c (value_user_defined_op): Likewise.
* valops.c (typecmp): Change parameter type from array pointer to
array_view. Update header comment, and update body accordingly.
(search_struct_method): Likewise.
(value_struct_elt): Likewise.
* value.h (value_struct_elt): Update declaration.
gdb/testsuite/ChangeLog:
PR gdb/27994
* gdb.cp/method-call-in-c.cc (struct foo_type): Add operator+=,
change initial value of var member variable.
(main): Make use of foo_type's operator+=.
* gdb.cp/method-call-in-c.exp: Test use of operator+=.
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I'm running into this assertion failure:
...
$ gdb -batch -ex "p (void *)0 - 5i"
gdbtypes.c:3430: internal-error: \
type* init_complex_type(const char*, type*): Assertion \
`target_type->code () == TYPE_CODE_INT \
|| target_type->code () == TYPE_CODE_FLT' failed.
A problem internal to GDB has been detected,
further debugging may prove unreliable.
...
This is a regression since commit c34e8714662 "Implement complex arithmetic".
Before that commit we had:
...
(gdb) p (void *)0 - 5i
Argument to arithmetic operation not a number or boolean.
...
Fix this in complex_binop by throwing an error, such that we have:
...
(gdb) print (void *)0 - 5i
Argument to complex arithmetic operation not supported.
...
Tested on x86_64-linux.
gdb/ChangeLog:
2021-02-05 Tom de Vries <tdevries@suse.de>
PR exp/27265
* valarith.c (complex_binop): Throw an error if complex type can't
be created.
gdb/testsuite/ChangeLog:
2021-02-05 Tom de Vries <tdevries@suse.de>
PR exp/27265
* gdb.base/complex-parts.exp: Add tests.
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... and update all users.
gdb/ChangeLog:
* gdbtypes.h (get_type_arch): Rename to...
(struct type) <arch>: ... this, update all users.
Change-Id: I0e3ef938a0afe798ac0da74a9976bbd1d082fc6f
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Testing showed that gdb was not correctly handling some fixed-point
binary operations correctly.
Addition and subtraction worked by casting the result to the type of
left hand operand. So, "fixed+int" had a different type -- and
different value -- from "int+fixed".
Furthermore, for multiplication and division, it does not make sense
to first cast both sides to the fixed-point type. For example, this
can prevent "f * 1" from yielding "f", if 1 is not in the domain of
"f". Instead, this patch changes gdb to use the value. (This is
somewhat different from Ada semantics, as those can yield a "universal
fixed point".)
This includes a new test case. It is only run in "minimal" mode, as
the old-style fixed point works differently, and is obsolete, so I
have no plans to change it.
gdb/ChangeLog
2021-01-06 Tom Tromey <tromey@adacore.com>
* ada-lang.c (ada_evaluate_subexp) <BINOP_ADD, BINOP_SUB>:
Do not cast result.
* valarith.c (fixed_point_binop): Handle multiplication
and division specially.
* valops.c (value_to_gdb_mpq): New function.
(value_cast_to_fixed_point): Use it.
gdb/testsuite/ChangeLog
2021-01-06 Tom Tromey <tromey@adacore.com>
* gdb.ada/fixed_points/pck.ads (Delta4): New constant.
(FP4_Type): New type.
(FP4_Var): New variable.
* gdb.ada/fixed_points/fixed_points.adb: Update.
* gdb.ada/fixed_points.exp: Add tests for binary operators.
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This commits the result of running gdb/copyright.py as per our Start
of New Year procedure...
gdb/ChangeLog
Update copyright year range in copyright header of all GDB files.
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fixed_point_binop did not account for division by zero. This would
lead to gdb getting SIGFPE and subsequently cause some test cases to
hang.
gdb/ChangeLog
2020-12-14 Tom Tromey <tromey@adacore.com>
* valarith.c (fixed_point_binop): Call error on division by zero.
gdb/testsuite/ChangeLog
2020-12-14 Tom Tromey <tromey@adacore.com>
* gdb.dwarf2/dw2-fixed-point.exp: Add test for division by zero.
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Since commit 7c6f27129631 ("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 7c6f27129631, 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 7c6f27129631 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 7c6f27129631. 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
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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
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gdb/ChangeLog (Simon Marchi <simark@simark.ca>):
* valarith.c (fixed_point_binop): Replace the
INIT_VAL_WITH_FIXED_POINT_VAL macro by a lambda. Update all
users accordingly.
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This logically connects this function to the object it inspects.
gdb/ChangeLog:
* gdbtypes.h (struct type) <fixed_point_scaling_factor>: New method,
replacing fixed_point_scaling_factor. All callers updated
throughout this project.
(fixed_point_scaling_factor): Delete declaration.
* gdbtypes.c (type::fixed_point_scaling_factor): Replaces
fixed_point_scaling_factor. Adjust implementation accordingly.
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This commit changes the interfaces of some of the methods declared
in gmp-utils to take a gdb::array_view of gdb_byte instead of a
(gdb_byte *, size) couple.
This makes these methods' API probably more C++-idiomatic.
* gmp-utils.h (gdb_mpz::read): Change buf and len parameters
into one single gdb::array_view parameter.
(gdb_mpz::write): Likewise.
(gdb_mpq::read_fixed_point, gdb_mpq::write_fixed_point): Likewise.
* gmp-utils.c (gdb_mpz::read): Change buf and len parameters
into one single gdb::array_view parameter.
Adjust implementation accordingly.
(gdb_mpz::write): Likewise.
(gdb_mpq::read_fixed_point, gdb_mpq::write_fixed_point): Likewise.
* unittests/gmp-utils-selftests.c: Adapt following changes above.
* valarith.c, valops.c, valprint.c, value.c: Likewise.
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This patch adds support for binary comparison operators with
fixed-point type values.
gdb/ChangeLog:
* valarith.c (fixed_point_binop): Add BINOP_EQUAL and BINOP_LESS
handling.
(value_less): Add fixed-point handling.
gdb/testsuite/ChangeLog:
* gdb.ada/fixed_cmp.exp: Add -fgnat-encodings=minimal testing.
* gdb.dwarf2/dw2-fixed-point.c (pck__fp1_var2): New global.
(main): Add reference to pck__fp1_var2.
* gdb.dwarf2/dw2-fixed-point.exp: Add comparison operator testing.
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This patch adds support for binary operations on fixed-point values,
as well as for the negative unary operator.
gdb/ChangeLog:
* eval.c (binop_promote): Add fixed-point type handling.
* valarith.c (fixed_point_binop): New function.
(scalar_binop): Add fixed-point type handling.
(value_neg): Add fixed-point type handling.
* valops.c (value_cast_to_fixed_point): New function.
(value_cast): Add fixed-point type handling.
gdb/testsuite/ChangeLog:
* gdb.dwarf2/dw2-fixed-point.exp: Add arithmetic tests.
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