This patch simplifies ada_lookup_struct_elt_type by changing it to
call find_struct_field. The two functions were substantially similar,
even to the point of having identical comments.
I tested this using both the gdb test suite and the internal AdaCore
test suite. Given this and the fact that it is Ada-specific, I am
checking it in.
History Of This Patch
=====================
This commit aims to address PR gdb/21699. There have now been a
couple of attempts to fix this issue. Simon originally posted two
patches back in 2021:
https://sourceware.org/pipermail/gdb-patches/2021-July/180894.htmlhttps://sourceware.org/pipermail/gdb-patches/2021-July/180896.html
Before Pedro then posted a version of his own:
https://sourceware.org/pipermail/gdb-patches/2021-July/180970.html
After this the conversation halted. Then in 2023 I (Andrew) also took
a look at this bug and posted two versions:
https://sourceware.org/pipermail/gdb-patches/2023-April/198570.htmlhttps://sourceware.org/pipermail/gdb-patches/2023-April/198680.html
The approach taken in my first patch was pretty similar to what Simon
originally posted back in 2021. My second attempt was only a slight
variation on the first.
Pedro then pointed out his older patch, and so we arrive at this
patch. The GDB changes here are mostly Pedro's work, but updated by
me (Andrew), any mistakes are mine.
The tests here are a combinations of everyone's work, and the commit
message is new, but copies bits from everyone's earlier work.
Problem Description
===================
Bug PR gdb/21699 makes the observation that using $_as_string with
GDB's printf can cause GDB to print unexpected data from the
inferior. The reproducer is pretty simple:
#include <stddef.h>
static char arena[100];
/* Override malloc() so value_coerce_to_target() gets a known
pointer, and we know we"ll see an error if $_as_string() gives
a string that isn't null terminated. */
void
*malloc (size_t size)
{
memset (arena, 'x', sizeof (arena));
if (size > sizeof (arena))
return NULL;
return arena;
}
int
main ()
{
return 0;
}
And then in a GDB session:
$ gdb -q test
Reading symbols from /tmp/test...
(gdb) start
Temporary breakpoint 1 at 0x4004c8: file test.c, line 17.
Starting program: /tmp/test
Temporary breakpoint 1, main () at test.c:17
17 return 0;
(gdb) printf "%s\n", $_as_string("hello")
"hello"xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
(gdb) quit
The problem above is caused by how value_cstring is used within
py-value.c, but once we understand the issue then it turns out that
value_cstring is used in an unexpected way in many places within GDB.
Within py-value.c we have a null-terminated C-style string. We then
pass a pointer to this string, along with the length of this
string (so not including the null-character) to value_cstring.
In value_cstring GDB allocates an array value of the given character
type, and copies in requested number of characters. However
value_cstring does not add a null-character of its own. This means
that the value created by calling value_cstring is only
null-terminated if the null-character is included in the passed in
length. In py-value.c this is not the case, and indeed, in most uses
of value_cstring, this is not the case.
When GDB tries to print one of these strings the value contents are
pushed to the inferior, and then read back as a C-style string, that
is, GDB reads inferior memory until it finds a null-terminator. For
the py-value.c case, no null-terminator is pushed into the inferior,
so GDB will continue reading inferior memory until a null-terminator
is found, with unpredictable results.
Patch Description
=================
The first thing this patch does is better define what the arguments
for the two function value_cstring and value_string should represent.
The comments in the header file are updated to describe whether the
length argument should, or should not, include a null-character.
Also, the data argument is changed to type gdb_byte. The functions as
they currently exist will handle wide-characters, in which case more
than one 'char' would be needed for each character. As such using
gdb_byte seems to make more sense.
To avoid adding casts throughout GDB, I've also added an overload that
still takes a 'char *', but asserts that the character type being used
is of size '1'.
The value_cstring function is now responsible for adding a null
character at the end of the string value it creates.
However, once we start looking at how value_cstring is used, we
realise there's another, related, problem. Not every language's
strings are null terminated. Fortran and Ada strings, for example,
are just an array of characters, GDB already has the function
value_string which can be used to create such values.
Consider this example using current GDB:
(gdb) set language ada
(gdb) p $_gdb_setting("arch")
$1 = (97, 117, 116, 111)
(gdb) ptype $
type = array (1 .. 4) of char
(gdb) p $_gdb_maint_setting("test-settings string")
$2 = (0)
(gdb) ptype $
type = array (1 .. 1) of char
This shows two problems, first, the $_gdb_setting and
$_gdb_maint_setting functions are calling value_cstring using the
builtin_char character, rather than a language appropriate type. In
the first call, the 'arch' case, the value_cstring call doesn't
include the null character, so the returned array only contains the
expected characters. But, in the $_gdb_maint_setting example we do
end up including the null-character, even though this is not expected
for Ada strings.
This commit adds a new language method language_defn::value_string,
this function takes a pointer and length and creates a language
appropriate value that represents the string. For C, C++, etc this
will be a null-terminated string (by calling value_cstring), and for
Fortran and Ada this can be a bounded array of characters with no null
terminator. Additionally, this new language_defn::value_string
function is responsible for selecting a language appropriate character
type.
After this commit the only calls to value_cstring are from the C
expression evaluator and from the default language_defn::value_string.
And the only calls to value_string are from Fortan, Ada, and ObjectC
related code.
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=21699
Co-Authored-By: Simon Marchi <simon.marchi@efficios.com>
Co-Authored-By: Andrew Burgess <aburgess@redhat.com>
Co-Authored-By: Pedro Alves <pedro@palves.net>
Approved-By: Simon Marchi <simon.marchi@efficios.com>
Remove the bp_location_pointer_iterator layer. Adjust all users of
breakpoint::locations to use references instead of pointers.
Change-Id: Iceed34f5e0f5790a9cf44736aa658be6d1ba1afa
Reviewed-By: Andrew Burgess <aburgess@redhat.com>
Add three convenience methods to struct breakpoint:
- has_locations: returns true if the breakpoint has at least one
location
- has_single_location: returns true if the breakpoint has exactly one
location
- has_multiple_locations: returns true if the breakpoint has more than
one location
A subsequent patch changes the list of breakpoints to be an
intrusive_list, so all these spots would need to change. But in any
case, I think that this:
if (b->has_multiple_locations ())
conveys the intention better than:
if (b->loc != nullptr && b->loc->next != nullptr)
Change-Id: Ib18c3605fd35d425ef9df82cb7aacff1606c6747
Reviewed-By: Andrew Burgess <aburgess@redhat.com>
The print_it method itself is const. In a subsequent patch, the
locations that come out of a const breakpoint will be const as well. It
will therefore be needed to make the last_loc output parameter const as
well. Make that change now to reduce the size of the following patches.
Change-Id: I7ed962950bc9582646e31e2e42beca2a1c9c5105
Reviewed-By: Andrew Burgess <aburgess@redhat.com>
A co-worker here at AdaCore discovered that the Pragma Import series
caused a rgression. When debugging gnat1, gdb started asking for
overload resolution like:
(gdb) call pp(n)
Multiple matches for pp
[0] cancel
[1] pp (types.union_id) at ../../gcc/gcc/ada/treepr.adb:511
[2] treepr.pp (types.union_id) at ../../gcc/gcc/ada/treepr.adb:511
This worked before the series, and is strange anyway, because the
matches refer to the same function.
This patch adds a test case for this situation and fixes the bug by
pruning identical functions in remove_extra_symbols.
I noticed many spots checking whether a dynamic property's kind is
PROP_CONST. Some spots, I think, are doing a slightly incorrect check
-- checking for != PROP_UNDEFINED where == PROP_CONST is actually
required, the key thing being that const_val may only be called for
PROP_CONST properties.
This patch adds dynamic::is_constant and then updates these checks to
use it.
Regression tested on x86-64 Fedora 36.
A co-worker at AdaCore noticed that calling a function without
debuginfo yields:
(gdb) print plus_one(23)
'pck.plus_one' has unknown return type; cast the call to its declared return type
However, this also happens if you follow the directions and add the
cast.
This patch fixes the problem and adds a regression test.
I think that the language_auto enumerator and the auto_language class
can be removed. There isn't really an "auto" language, it's only a
construct of the "set language" command to say "pick the appropriate
language automatically". But "auto" is never the current language. The
`current_language` points to the current effective language, and the
fact that we're in "auto language" mode is noted by the language_mode
global.
- Change set_language to handle the "auto" (and "local", which is a
synonym) early, instead of in the for loop. I think it makes the two
cases (auto vs explicit language) more clearly separated anyway.
- Adjust add_set_language_command to hard-code the "auto" string,
instead of using the "auto" language definition.
- Remove auto_language, rename auto_or_unknown_language to
unknown_language and move the bits of the existing unknown_language
in there.
- Remove the set_language at the end of _initialize_language. I think
it's not needed, because we call set_language in gdb_init, after all
_initialize functions are called. There is some chance that an
_initialize function that runs after _initialize_language implicitly
depends on current_language being set, but my testsuite runs haven't
found anything like that.
- Use language_unknown instead of language_auto when creating a minimal
symbol (minimal_symbol_reader::record_full). I think that this value
is used to indicate that we don't know the symbol of the minimal
symbol (yet), so language_unknown makes sense to me. Update a
condition accordingly in ada-lang.c. symbol_find_demangled_name also
appears to "normalize" this value from "unknown" to "auto", remove
that part and update the condition to just check for
language_unknown.
Change-Id: I47bcd6c15f607d9818f2e6e413053c2dc8ec5034
Reviewed-By: Tom Tromey <tom@tromey.com>
I noticed some unnecessary casts to LONGEST in ada-lang.c. This patch
removes the ones I think are very clearly not needed. I'm checking
this in as obvious.
In an experiment I'm trying, I needed Ada symbol cache entries to be
allocated with 'new'. This patch reimplements the symbol cache to use
the libiberty hash table and to use new and delete. A couple of other
minor cleanups are done.
This changes the array type creation functions to accept a type
allocator, and updates all the callers. Note that symbol readers
should generally allocate on the relevant objfile, regardless of the
placement of the index type of the array, which is what this patch
implements.
Reviewed-By: Simon Marchi <simon.marchi@efficios.com>
This changes the range type creation functions to accept a type
allocator, and updates all the callers. Note that symbol readers
should generally allocate on the relevant objfile, regardless of the
underlying type of the range, which is what this patch implements.
Reviewed-By: Simon Marchi <simon.marchi@efficios.com>
As described in the previous commit for this series, I became
concerned that there might be instances in which a QUIT (due to either
a SIGINT or SIGTERM) might not cause execution to return to the top
level. In some (though very few) instances, it is okay to not
propagate the exception for a Ctrl-C / SIGINT, but I don't think that
it is ever okay to swallow the exception caused by a SIGTERM.
Allowing that to happen would definitely be a deviation from the
current behavior in which GDB exits upon receipt of a SIGTERM.
I looked at all cases where an exception handler catches a
gdb_exception. Handlers which did NOT need modification were those
which satisifed one or more of the following conditions:
1) There is no call path to maybe_quit() in the try block. I used a
static analysis tool to help make this determination. In
instances where the tool didn't provide an answer of "yes, this
call path can result in maybe_quit() being called", I reviewed it
by hand.
2) The catch block contains a throw for conditions that it
doesn't want to handle; these "not handled" conditions
must include the quit exception and the new "forced quit" exception.
3) There was (also) a catch for gdb_exception_quit.
Any try/catch blocks not meeting the above conditions could
potentially swallow a QUIT exception.
My first thought was to add catch blocks for gdb_exception_quit and
then rethrow the exception. But Pedro pointed out that this can be
handled without adding additional code by simply catching
gdb_exception_error instead. That's what this patch series does.
There are some oddball cases which needed to be handled differently,
plus the extension languages, but those are handled in later patches.
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=26761
Tested-by: Tom de Vries <tdevries@suse.de>
Approved-by: Pedro Alves <pedro@palves.net>
Ada historically has not implemented agent expressions, and some Ada
constructs probably cannot reasonably be converted to agent
expressions. However, a subset of simple operations can be, and this
patch represents a first step in that direction.
On one internal AdaCore test case, this improves the performance of a
conditional breakpoint from 5 minutes to 5 seconds.
The main tricky part in this patch is ensuring the converted
expressions detect the cases that will not work. This is done by
examining the code in the corresponding evaluation methods.
This changes the block_iterator to store the 'name' that is used by
block_iter_match_next. This avoids any problem where the name could
be passed inconsistently, and also makes the subsequent patches easier
to understand.
This converts block_static_block and block_global_block to be methods.
This was mostly written by script. It was simpler to convert them at
the same time because they're often used near each other.
This converts block_scope, block_set_scope, block_using, and
block_set_using to be methods. These are all done at once to make it
easier to also convert block_initialize_namespace at the same time.
This was mostly written by script.
create_ada_exception_catchpoint has a parameter named "disabled", but
both its callers and callees use it to mean "enabled". This is
confusing, so this patch renames the parameter.
Unlike the other *_main_name functions, ada_main_name returns a
non-const "char *". This is strange, though, because the caller
should not in fact modify or free this pointer. This patch changes
this function to constify its return type.
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>
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>
This patch turns a grab bag of value functions to methods of value.
These are done together because their implementations are
interrelated.
Approved-By: Simon Marchi <simon.marchi@efficios.com>
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>
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>
This changes value_fetch_lazy to be a method of value. A few helper
functions are converted as well, to avoid problems in later patches
when the data members are all made private.
Approved-By: Simon Marchi <simon.marchi@efficios.com>
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>
