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Following on from the previous commit, this updates
Frame.read_register to accept named arguments. As with the previous
commit there's no huge benefit for the users in accepting named
arguments here -- this function only takes a single argument after
all.
But I do think it is worth keeping Frame.read_register method in sync
with the PendingFrame.read_register method, this allows for the
possibility that the user has some code that can operate on either a
Frame or a Pending frame.
Minor update to allow for named arguments, and an extra test to check
the new functionality.
Reviewed-By: Tom Tromey <tom@tromey.com>
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Update the two gdb.PendingFrame methods gdb.PendingFrame.read_register
and gdb.PendingFrame.create_unwind_info to accept keyword arguments.
There's no huge benefit for making this change, both of these methods
only take a single argument, so it is (maybe) less likely that a user
will take advantage of the keyword arguments in these cases, but I
think it's nice to be consistent, and I don't see any particular draw
backs to making this change.
For PendingFrame.read_register I've changed the argument name from
'reg' to 'register' in the documentation and used 'register' as the
argument name in GDB. My preference for APIs is to use full words
where possible, and given we didn't support named arguments before
this change should not break any existing code.
There should be no user visible changes (for existing code) after this
commit.
Reviewed-By: Eli Zaretskii <eliz@gnu.org>
Reviewed-By: Tom Tromey <tom@tromey.com>
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Update gdb.UnwindInfo.add_saved_register to accept named keyword
arguments.
As part of this update we now use gdb_PyArg_ParseTupleAndKeywords
instead of PyArg_UnpackTuple to parse the function arguments.
By switching to gdb_PyArg_ParseTupleAndKeywords, we can now use 'O!'
as the argument format for the function's value argument. This means
that we can check the argument type (is gdb.Value) as part of the
argument processing rather than manually performing the check later in
the function. One result of this is that we now get a better error
message (at least, I think so). Previously we would get something
like:
ValueError: Bad register value
Now we get:
TypeError: argument 2 must be gdb.Value, not XXXX
It's unfortunate that the exception type changed, but I think the new
exception type actually makes more sense.
My preference for argument names is to use full words where that's not
too excessive. As such, I've updated the name of the argument from
'reg' to 'register' in the documentation, which is the argument name
I've made GDB look for here.
For existing unwinder code that doesn't throw any exceptions nothing
should change with this commit. It is possible that a user has some
code that throws and catches the ValueError, and this code will break
after this commit, but I think this is going to be sufficiently rare
that we can take the risk here.
Reviewed-By: Eli Zaretskii <eliz@gnu.org>
Reviewed-By: Tom Tromey <tom@tromey.com>
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This commit aims to address a problem that exists with the current
approach to displaced stepping, and was identified in PR gdb/22921.
Displaced stepping is currently supported on AArch64, ARM, amd64,
i386, rs6000 (ppc), and s390. Of these, I believe there is a problem
with the current approach which will impact amd64 and ARM, and can
lead to random register corruption when the inferior makes use of
asynchronous signals and GDB is using displaced stepping.
The problem can be found in displaced_step_buffers::finish in
displaced-stepping.c, and is this; after GDB tries to perform a
displaced step, and the inferior stops, GDB classifies the stop into
one of two states, either the displaced step succeeded, or the
displaced step failed.
If the displaced step succeeded then gdbarch_displaced_step_fixup is
called, which has the job of fixing up the state of the current
inferior as if the step had not been performed in a displaced manner.
This all seems just fine.
However, if the displaced step is considered to have not completed
then GDB doesn't call gdbarch_displaced_step_fixup, instead GDB
remains in displaced_step_buffers::finish and just performs a minimal
fixup which involves adjusting the program counter back to its
original value.
The problem here is that for amd64 and ARM setting up for a displaced
step can involve changing the values in some temporary registers. If
the displaced step succeeds then this is fine; after the step the
temporary registers are restored to their original values in the
architecture specific code.
But if the displaced step does not succeed then the temporary
registers are never restored, and they retain their modified values.
In this context a temporary register is simply any register that is
not otherwise used by the instruction being stepped that the
architecture specific code considers safe to borrow for the lifetime
of the instruction being stepped.
In the bug PR gdb/22921, the amd64 instruction being stepped is
an rip-relative instruction like this:
jmp *0x2fe2(%rip)
When we displaced step this instruction we borrow a register, and
modify the instruction to something like:
jmp *0x2fe2(%rcx)
with %rcx having its value adjusted to contain the original %rip
value.
Now if the displaced step does not succeed, then %rcx will be left
with a corrupted value. Obviously corrupting any register is bad; in
the bug report this problem was spotted because %rcx is used as a
function argument register.
And finally, why might a displaced step not succeed? Asynchronous
signals provides one reason. GDB sets up for the displaced step and,
at that precise moment, the OS delivers a signal (SIGALRM in the bug
report), the signal stops the inferior at the address of the displaced
instruction. GDB cancels the displaced instruction, handles the
signal, and then tries again with the displaced step. But it is that
first cancellation of the displaced step that causes the problem; in
that case GDB (correctly) sees the displaced step as having not
completed, and so does not perform the architecture specific fixup,
leaving the register corrupted.
The reason why I think AArch64, rs600, i386, and s390 are not effected
by this problem is that I don't believe these architectures make use
of any temporary registers, so when a displaced step is not completed
successfully, the minimal fix up is sufficient.
On amd64 we use at most one temporary register.
On ARM, looking at arm_displaced_step_copy_insn_closure, we could
modify up to 16 temporary registers, and the instruction being
displaced stepped could be expanded to multiple replacement
instructions, which increases the chances of this bug triggering.
This commit only aims to address the issue on amd64 for now, though I
believe that the approach I'm proposing here might be applicable for
ARM too.
What I propose is that we always call gdbarch_displaced_step_fixup.
We will now pass an extra argument to gdbarch_displaced_step_fixup,
this a boolean that indicates whether GDB thinks the displaced step
completed successfully or not.
When this flag is false this indicates that the displaced step halted
for some "other" reason. On ARM GDB can potentially read the
inferior's program counter in order figure out how far through the
sequence of replacement instructions we got, and from that GDB can
figure out what fixup needs to be performed.
On targets like amd64 the problem is slightly easier as displaced
stepping only uses a single replacement instruction. If the displaced
step didn't complete the GDB knows that the single instruction didn't
execute.
The point is that by always calling gdbarch_displaced_step_fixup, each
architecture can now ensure that the inferior state is fixed up
correctly in all cases, not just the success case.
On amd64 this ensures that we always restore the temporary register
value, and so bug PR gdb/22921 is resolved.
In order to move all architectures to this new API, I have moved the
minimal roll-back version of the code inside the architecture specific
fixup functions for AArch64, rs600, s390, and ARM. For all of these
except ARM I think this is good enough, as no temporaries are used all
that's needed is the program counter restore anyway.
For ARM the minimal code is no worse than what we had before, though I
do consider this architecture's displaced-stepping broken.
I've updated the gdb.arch/amd64-disp-step.exp test to cover the
'jmpq*' instruction that was causing problems in the original bug, and
also added support for testing the displaced step in the presence of
asynchronous signal delivery.
I've also added two new tests (for amd64 and i386) that check that GDB
can correctly handle displaced stepping over a single instruction that
branches to itself. I added these tests after a first version of this
patch relied too much on checking the program-counter value in order
to see if the displaced instruction had executed. This works fine in
almost all cases, but when an instruction branches to itself a pure
program counter check is not sufficient. The new tests expose this
problem.
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=22921
Approved-By: Pedro Alves <pedro@palves.net>
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Oops, tried to free too much
* wrstabs.c (write_stabs_in_sections_debugging_info): Don't
free strings.
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Fix memory leaks and do a general tidy of the code for printing coff
and stabs debug.
* prdbg.c: Delete unnneeded forward function declarations.
Delete unnecessary casts throughout. Free all strings
returned from pop_type throughout file.
(struct pr_stack): Delete "num_parents". Replace tests for
"num_parents" non-zero with tests of "parents" non-NULL
throughout. Free "parents" before assigning, and set to NULL
after freeing. Remove const from "method". Always strdup
strings assigned to method, and free before assigning.
(print_debugging_info): Free info.stack and info.filename.
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objdump -g can't be used much. Trying to dump PE files invariably
seems to run into "debug_name_type: no current file" or similar
errors, because parse_coff expects a C_FILE symbol to be the first
symbol. Dumping -gstabs output works since the N_SO stab is present.
Pre-setting the file name won't hurt stabs dumping.
* rddbg.c (read_debugging_info): Call debug_set_filename.
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A tiny tidy.
* write.c (frags_chained): Make it a bool.
(n_fixups): Make it unsigned.
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The old stabs code didn't bother too much about freeing memory.
This patch corrects that and avoids some dubious copying of strings.
* objcopy.c (write_debugging_info): Free both strings and
syms on failure to create sections.
* wrstabs.c: Delete unnecessary forward declarations and casts
throughout file.
(stab_write_symbol_and_free): New function. Use it
throughout, simplifying return paths.
(stab_push_string): Don't strdup string. Use it thoughout
for malloced strings.
(stab_push_string_dup): New function. Use it throughout for
strings in auto buffers.
(write_stabs_in_sections_debugging_info): Free malloced memory.
(stab_enum_type): Increase buffer sizing for worst case.
(stab_range_type, stab_array_type): Reduce buffer size.
(stab_set_type): Likewise.
(stab_method_type): Free args on error return. Correct
buffer size.
(stab_struct_field): Fix memory leaks.
(stab_class_static_member, stab_class_baseclass): Likewise.
(stab_start_class_type): Likewise. Correct buffer size.
(stab_class_start_method): Correct buffer size.
(stab_class_method_var): Free memory on error return.
(stab_start_function): Fix "rettype" memory leak.
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The stabs debug format is obsolete and there's no reason to think that
toolchains still have good support for it. Therefore, if a specific debug
format wasn't set in asm-source.exp then leave it to the assembler to
decide which one to use.
Reviewed-By: Tom Tromey <tom@tromey.com>
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After commit 9675da25357c ("Use unrelocated_addr in minimal symbols"),
aarch64-linux started failing gdb.asm/asm-source.exp:
Running /home/thiago.bauermann/src/binutils-gdb/gdb/testsuite/gdb.asm/asm-source.exp ...
PASS: gdb.asm/asm-source.exp: f at main
PASS: gdb.asm/asm-source.exp: n at main
PASS: gdb.asm/asm-source.exp: next over macro
FAIL: gdb.asm/asm-source.exp: step into foo2
PASS: gdb.asm/asm-source.exp: info target
PASS: gdb.asm/asm-source.exp: info symbol
PASS: gdb.asm/asm-source.exp: list
PASS: gdb.asm/asm-source.exp: search
FAIL: gdb.asm/asm-source.exp: f in foo2
FAIL: gdb.asm/asm-source.exp: n in foo2 (the program exited)
FAIL: gdb.asm/asm-source.exp: bt ALL in foo2
FAIL: gdb.asm/asm-source.exp: bt 2 in foo2
PASS: gdb.asm/asm-source.exp: s 2
PASS: gdb.asm/asm-source.exp: n 2
FAIL: gdb.asm/asm-source.exp: bt 3 in foo3
PASS: gdb.asm/asm-source.exp: info source asmsrc1.s
FAIL: gdb.asm/asm-source.exp: finish from foo3 (the program is no longer running)
FAIL: gdb.asm/asm-source.exp: info source asmsrc2.s
PASS: gdb.asm/asm-source.exp: info sources
FAIL: gdb.asm/asm-source.exp: info line
FAIL: gdb.asm/asm-source.exp: next over foo3 (the program is no longer running)
FAIL: gdb.asm/asm-source.exp: return from foo2
PASS: gdb.asm/asm-source.exp: look at global variable
PASS: gdb.asm/asm-source.exp: x/i &globalvar
PASS: gdb.asm/asm-source.exp: disassem &globalvar, (int *) &globalvar+1
PASS: gdb.asm/asm-source.exp: look at static variable
PASS: gdb.asm/asm-source.exp: x/i &staticvar
PASS: gdb.asm/asm-source.exp: disassem &staticvar, (int *) &staticvar+1
PASS: gdb.asm/asm-source.exp: look at static function
The problem is simple: a pair of parentheses was removed from the
expression calculating text_end and thus text_size was only added if
lowest_text_address wasn't equal to -1.
This patch restores the previous behaviour and fixes the testcase.
Tested on native aarch64-linux.
Reviewed-By: Tom Tromey <tom@tromey.com>
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MPFR is now mandatory, so its previous description in Requirements
was inappropriate and out of place. In addition, the description
of how to go about specifying 'configure' time options for
building with libraries was highly repetitive. Some of the text
was also outdated and used wrong markup.
Original patch and suggestions from Philippe Blain
<levraiphilippeblain@gmail.com>.
ChangeLog:
2023-04-05 Eli Zaretskii <eliz@gnu.org>
* gdb/doc/gdb.texinfo (Requirements, Configure Options): Update and
rearrange; improve and fix markup.
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The 'info threads' command does not show the '-gid' option
in the syntax. Add the option. The flag is already explained
in the command description and used in the examples.
Approved-By: Eli Zaretskii <eliz@gnu.org>
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Convert the return type of 'should_print_thread' from int to bool.
Reviewed-By: Tom Tromey <tom@tromey.com>
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Make find_thread_ptid (the overload that takes a process_stratum_target)
a method of process_stratum_target.
Change-Id: Ib190a925a83c6b93e9c585dc7c6ab65efbdd8629
Reviewed-By: Tom Tromey <tom@tromey.com>
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Make find_thread_ptid (the overload that takes an inferior) a method of
struct inferior.
Change-Id: Ie5b9fa623ff35aa7ddb45e2805254fc8e83c9cd4
Reviewed-By: Tom Tromey <tom@tromey.com>
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Having been irritated by seeing bfd/elf{32,64}-aarch64.c to be re-
generated in x86-only builds, I came across 769a27ade588 ("Re: bfd
BLD-POTFILES.in dependencies"). I think this went slightly too far, as
outside of maintainer mode dependencies will cause the subset of files
to be (re-)generated which are actually needed for the build.
Generating them all is only needed when wanting to update certain files
under bfd/po/, i.e. in maintainer mode.
In the course of looking around in an attempt to try to understand how
things are meant to work, I further noticed that ld has got things
slightly wrong too: BLD-POTFILES.in depending on $(BLD_POTFILES) isn't
quite right (the output doesn't change when any of the enumerated files
changes; it's the mere presence which matters); like in bfd it looks
like we would better extend BUILT_SOURCES accordingly.
Furthermore it became apparent that ld fails to enumerate the .c files
generated from the .l and .y ones. While in their absence it was benign
whether translatable strings in the source files were actually marked as
such, this now becomes relevant. Mark respective strings at the same
time, but skipping ones which look to be of interest for debugging
purposes only (e.g. such used by printf() enclosed in #ifdef TRACE).
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Trying to free malloc'd memory used by the stabs and coff debug info
parsers is complicated, and traversing the trees generated requires a
lot of code. It's better to bfd_alloc the memory which allows it all
to be freed without fuss when the bfd is closed. In the process of
doing this I reverted most of commit a6336913332.
Some of the stabs handling code grows arrays of pointers with realloc,
to deal with arbitrary numbers of fields, function args, etc. The
code still does that but copies over to bfd_alloc memory when
finished. The alternative is to parse twice, once to size, then again
to populate the arrays. I think that complication is unwarranted.
Note that there is a greater than zero chance this patch breaks
something, eg. that I missed an attempt to free obj_alloc memory.
Also it seems there are no tests in the binutils testsuite aimed at
exercising objdump --debugging.
* budbg.h (finish_stab, parse_stab): Update prototypes
* debug.c: Include bucomm.h.
(struct debug_handle): Add "abfd" field.
(debug_init): Add "abfd" param. bfd_alloc handle.
(debug_xalloc, debug_xzalloc): New functions. Use throughout
in place of xmalloc and memset.
(debug_start_source): Remove "name_used" param.
* debug.h (debug_init, debug_start_source): Update prototypes.
(debug_xalloc, debug_xzalloc): Declare.
* objcopy.c (copy_object): Don't free dhandle.
* objdump.c (dump_bfd): Likewise.
* rdcoff.c (coff_get_slot): Add dhandle arg. debug_xzalloc
memory in place of xcalloc. Update callers.
(parse_coff_struct_type): Don't leak on error return. Copy
fields over to debug_xalloc memory.
(parse_coff_enum_type): Copy names and vals over the
debug_xalloc memory.
* rddbg.c (read_debugging_info): Adjust debug_init call.
Don't free dhandle.
(read_section_stabs_debugging_info): Don't free shandle.
Adjust parse_stab call. Call finish_stab on error return.
(read_symbol_stabs_debugging_info): Similarly.
* stabs.c (savestring): Delete unnecessary forward declaration.
Add dhandle param. debug_xalloc memory. Update callers.
(start_stab): Delete unnecessary casts.
(finish_stab): Add "emit" param. Free file_types, so_string,
and stabs handle.
(parse_stab): Delete string_used param. Revert code dealing
with string_used. Copy so_string passed to debug_set_filename
and stored as main_filename to debug_xalloc memory. Similarly
for string passed to debug_start_source and push_bincl. Copy
args to debug_xalloc memory. Don't leak args.
(parse_stab_enum_type): Copy names and values to debug_xalloc
memory. Don't free name.
(parse_stab_struct_type): Don't free fields.
(parse_stab_baseclasses): Delete unnecessary cast.
(parse_stab_struct_fields): Return debug_xalloc fields.
(parse_stab_cpp_abbrev): Use debug_xalloc for _vb$ type name.
(parse_stab_one_struct_field): Don't free name.
(parse_stab_members): Copy variants and methods to
debug_xalloc memory. Don't free name or argtypes.
(parse_stab_argtypes): Use debug_xalloc memory for physname
and args.
(push_bincl): Add dhandle param. Use debug_xalloc memory.
(stab_record_variable): Use debug_xalloc memory.
(stab_emit_pending_vars): Don't free var list.
(stab_find_slot): Add dhandle param. Use debug_xzalloc
memory. Update all callers.
(stab_find_tagged_type): Don't free name. Use debug_xzalloc.
(stab_demangle_qualified): Don't free name.
(stab_demangle_template): Don't free s1.
(stab_demangle_args): Tidy pvarargs refs. Copy *pargs on
success to debug_xalloc memory, free on failure.
(stab_demangle_fund_type): Don't free name.
(stab_demangle_v3_arglist): Copy args to debug_xalloc memory.
Don't free dt.
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This adds the DAP readMemory and writeMemory requests. A small change
to the evaluation code is needed in order to test this -- this is one
of the few ways for a client to actually acquire a memory reference.
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I noticed a couple of places in infrun.c where we call
set_momentary_breakpoint_at_pc, and then set the newly created
breakpoint's thread field, these are in:
insert_exception_resume_breakpoint
insert_exception_resume_from_probe
Function set_momentary_breakpoint_at_pc calls
set_momentary_breakpoint, which always creates the breakpoint as
thread-specific for the current inferior_thread().
The two insert_* functions mentioned above take an arbitrary
thread_info* as an argument and set the breakpoint::thread to hold the
thread number of that arbitrary thread.
However, the insert_* functions store the breakpoint pointer within
the current inferior_thread(), so we know that the thread being passed
in must be the currently selected thread.
What this means is that we can:
1. Assert that the thread being passed in is the currently selected
thread, and
2. No longer adjust the breakpoint::thread field, this will already
have been set correctly be calling set_momentary_breakpoint_at_pc.
There should be no user visible changes after this commit.
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Consider the following session:
(gdb) list some_func
1 int
2 some_func ()
3 {
4 int *p = 0;
5 return *p;
6 }
7
8 void
9 foo ()
10 {
(gdb) break foo if (some_func ())
Breakpoint 1 at 0x40111e: file bpcond.c, line 11.
(gdb) r
Starting program: /tmp/bpcond
Program received signal SIGSEGV, Segmentation fault.
0x0000000000401116 in some_func () at bpcond.c:5
5 return *p;
Error in testing condition for breakpoint 1:
The program being debugged stopped while in a function called from GDB.
Evaluation of the expression containing the function
(some_func) will be abandoned.
When the function is done executing, GDB will silently stop.
Breakpoint 1, 0x0000000000401116 in some_func () at bpcond.c:5
5 return *p;
(gdb)
What happens here is the breakpoint condition includes a call to an
inferior function, and the inferior function segfaults. We can see
that GDB reports the segfault, and then gives an error message that
indicates that an inferior function call was interrupted.
After this GDB appears to report that it is stopped at Breakpoint 1,
inside some_func.
I find this second stop report a little confusing. While it is true
that GDB stopped as a result of hitting breakpoint 1, I think the
message GDB currently prints might give the impression that GDB is
actually stopped at a location of breakpoint 1, which is not the case.
Also, I find the second stop message draws attention away from
the "Program received signal SIGSEGV, Segmentation fault" stop
message, and this second stop might be thought of as replacing in
someway the earlier message.
In short, I think things would be clearer if the second stop message
were not reported at all, so the output should, I think, look like
this:
(gdb) list some_func
1 int
2 some_func ()
3 {
4 int *p = 0;
5 return *p;
6 }
7
8 void
9 foo ()
10 {
(gdb) break foo if (some_func ())
Breakpoint 1 at 0x40111e: file bpcond.c, line 11.
(gdb) r
Starting program: /tmp/bpcond
Program received signal SIGSEGV, Segmentation fault.
0x0000000000401116 in some_func () at bpcond.c:5
5 return *p;
Error in testing condition for breakpoint 1:
The program being debugged stopped while in a function called from GDB.
Evaluation of the expression containing the function
(some_func) will be abandoned.
When the function is done executing, GDB will silently stop.
(gdb)
The user can still find the number of the breakpoint that triggered
the initial stop in this line:
Error in testing condition for breakpoint 1:
But there's now only one stop reason reported, the SIGSEGV, which I
think is much clearer.
To achieve this change I set the bpstat::print field when:
(a) a breakpoint condition evaluation failed, and
(b) the $pc of the thread changed during condition evaluation.
I've updated the existing tests that checked the error message printed
when a breakpoint condition evaluation failed.
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Consider the following case:
(gdb) list some_func
1 int
2 some_func ()
3 {
4 int *p = 0;
5 return *p;
6 }
7
8 void
9 foo ()
10 {
(gdb) break foo if (some_func ())
Breakpoint 1 at 0x40111e: file bpcond.c, line 11.
(gdb) r
Starting program: /tmp/bpcond
Program received signal SIGSEGV, Segmentation fault.
0x0000000000401116 in some_func () at bpcond.c:5
5 return *p;
Error in testing breakpoint condition:
The program being debugged was signaled while in a function called from GDB.
GDB remains in the frame where the signal was received.
To change this behavior use "set unwindonsignal on".
Evaluation of the expression containing the function
(some_func) will be abandoned.
When the function is done executing, GDB will silently stop.
Program received signal SIGSEGV, Segmentation fault.
Breakpoint 1, 0x0000000000401116 in some_func () at bpcond.c:5
5 return *p;
(gdb)
Notice that this line:
Program received signal SIGSEGV, Segmentation fault.
Appears twice in the output. The first time is followed by the
current location. The second time is a little odd, why do we print
that?
Printing that line is controlled, in part, by a global variable,
stopped_by_random_signal. This variable is reset to zero in
handle_signal_stop, and is set if/when GDB figures out that the
inferior stopped due to some random signal.
The problem is, in our case, GDB first stops at the breakpoint for
foo, and enters handle_signal_stop and the stopped_by_random_signal
global is reset to 0.
Later within handle_signal_stop GDB calls bpstat_stop_status, it is
within this function (via bpstat_check_breakpoint_conditions) that the
breakpoint condition is checked, and, we end up calling the inferior
function (some_func in our example above).
In our case above the thread performing the inferior function call
segfaults in some_func. GDB catches the SIGSEGV and handles the stop,
this causes us to reenter handle_signal_stop. The global variable
stopped_by_random_signal is updated, this time it is set to true
because the thread stopped due to SIGSEGV. As a result of this we
print the first instance of the line (as seen above in the example).
Finally we unwind GDB's call stack, the inferior function call is
complete, and we return to the original handle_signal_stop. However,
the stopped_by_random_signal global is still carrying the value as
computed for the inferior function call's stop, which is why we now
print a second instance of the line, as seen in the example.
To prevent this, I propose adding a scoped_restore before we start an
inferior function call. This will save and restore the global
stopped_by_random_signal value.
With this done, the output from our example is now this:
(gdb) list some_func
1 int
2 some_func ()
3 {
4 int *p = 0;
5 return *p;
6 }
7
8 void
9 foo ()
10 {
(gdb) break foo if (some_func ())
Breakpoint 1 at 0x40111e: file bpcond.c, line 11.
(gdb) r
Starting program: /tmp/bpcond
Program received signal SIGSEGV, Segmentation fault.
0x0000000000401116 in some_func () at bpcond.c:5
5 return *p;
Error in testing condition for breakpoint 1:
The program being debugged stopped while in a function called from GDB.
Evaluation of the expression containing the function
(some_func) will be abandoned.
When the function is done executing, GDB will silently stop.
Breakpoint 1, 0x0000000000401116 in some_func () at bpcond.c:5
5 return *p;
(gdb)
We now only see the 'Program received signal SIGSEGV, ...' line once,
which I think makes more sense.
Finally, I'm aware that the last few lines, that report the stop as
being at 'Breakpoint 1', when this is not where the thread is actually
located anymore, is not great. I'll address that in the next commit.
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This commit extends gdbserver to take account of a failed memory
access from agent_mem_read, and to return a new eval_result_type
expr_eval_invalid_memory_access.
I have only updated the agent_mem_read calls related directly to
reading memory, I have not updated any of the calls related to
tracepoint data collection. This is just because I'm not familiar
with that area of gdb/gdbserver, and I don't want to break anything,
so leaving the existing behaviour untouched seems like the safest
approach.
I've then updated gdb.base/bp-cond-failure.exp to test evaluating the
breakpoints on the target, and have also extended the test so that it
checks for different sizes of memory access.
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Currently the gdbserver function agent_mem_read ignores any errors
from calling read_inferior_memory. This means that if there is an
attempt to access invalid memory then this will appear to succeed.
In this patch I update agent_mem_read so that if read_inferior_memory
fails, agent_mem_read will return an error code.
However, none of the callers of agent_mem_read actually check the
return value, so this commit will have no effect on anything. In the
next commit I will update the users of agent_mem_read to check for the
error code.
I've also updated the header comments on agent_mem_read to better
reflect what the function does, and its possible return values.
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When GDB fails to test the condition of a conditional breakpoint, for
whatever reason, the error message looks like this:
(gdb) break foo if (*(int *) 0) == 1
Breakpoint 1 at 0x40111e: file bpcond.c, line 11.
(gdb) r
Starting program: /tmp/bpcond
Error in testing breakpoint condition:
Cannot access memory at address 0x0
Breakpoint 1, foo () at bpcond.c:11
11 int a = 32;
(gdb)
The line I'm interested in for this commit is this one:
Error in testing breakpoint condition:
In the case above we can figure out that the problematic breakpoint
was #1 because in the final line of the message GDB reports the stop
at breakpoint #1.
However, in the next few patches I plan to change this. In some cases
I don't think it makes sense for GDB to report the stop as being at
breakpoint #1, consider this case:
(gdb) list some_func
1 int
2 some_func ()
3 {
4 int *p = 0;
5 return *p;
6 }
7
8 void
9 foo ()
10 {
(gdb) break foo if (some_func ())
Breakpoint 1 at 0x40111e: file bpcond.c, line 11.
(gdb) r
Starting program: /tmp/bpcond
Program received signal SIGSEGV, Segmentation fault.
0x0000000000401116 in some_func () at bpcond.c:5
5 return *p;
Error in testing breakpoint condition:
The program being debugged was signaled while in a function called from GDB.
GDB remains in the frame where the signal was received.
To change this behavior use "set unwindonsignal on".
Evaluation of the expression containing the function
(some_func) will be abandoned.
When the function is done executing, GDB will silently stop.
Program received signal SIGSEGV, Segmentation fault.
Breakpoint 1, 0x0000000000401116 in some_func () at bpcond.c:5
5 return *p;
(gdb)
Notice that, the final lines of output reports the stop as being at
breakpoint #1, even though the inferior in not located within
some_func, and it's certainly not located at the breakpoint location.
I find this behaviour confusing, and propose that this should be
changed. However, if I make that change then every reference to
breakpoint #1 will be lost from the error message.
So, in this commit, in preparation for the later commits, I propose to
change the 'Error in testing breakpoint condition:' line to this:
Error in testing condition for breakpoint NUMBER:
where NUMBER will be filled in as appropriate. Here's the first
example with the updated error:
(gdb) break foo if (*(int *) 0) == 0
Breakpoint 1 at 0x40111e: file bpcond.c, line 11.
(gdb) r
Starting program: /tmp/bpcond
Error in testing condition for breakpoint 1:
Cannot access memory at address 0x0
Breakpoint 1, foo () at bpcond.c:11
11 int a = 32;
(gdb)
The breakpoint number does now appear twice in the output, but I don't
see that as a negative.
This commit just changes the one line of the error, and updates the
few tests that either included the old error in comments, or actually
checked for the error in the expected output.
As the only test that checked the line I modified is a Python test,
I've added a new test that doesn't rely on Python that checks the
error message in detail.
While working on the new test, I spotted that it would fail when run
with native-gdbserver and native-extended-gdbserver target boards.
This turns out to be due to a gdbserver bug. To avoid cluttering this
commit I've added a work around to the new test script so that the
test passes for the remote boards, in the next few commits I will fix
gdbserver, and update the test script to remove the work around.
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* csky-dis.c (csky_print_operand <OPRND_TYPE_FCONSTANT>): Don't
access ibytes after read_memory_func error. Change type of
ibytes to avoid casts.
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This commit builds on the previous one to fix all the remaining
failures in gdb.base/unwind-on-each-insn.exp for RISC-V.
The problem we have in gdb.base/unwind-on-each-insn.exp is that, when
we are in the function epilogue, the previous frame and stack pointer
values are being restored, and so, the values that we calculated
during the function prologue are no longer suitable.
Here's an example from the function 'bar' in the mentioned test. This
was compiled for 64-bit RISC-V with compressed instruction support:
Dump of assembler code for function bar:
0x000000000001018a <+0>: add sp,sp,-32
0x000000000001018c <+2>: sd ra,24(sp)
0x000000000001018e <+4>: sd fp,16(sp)
0x0000000000010190 <+6>: add fp,sp,32
0x0000000000010192 <+8>: sd a0,-24(fp)
0x0000000000010196 <+12>: ld a0,-24(fp)
0x000000000001019a <+16>: jal 0x10178 <foo>
0x000000000001019e <+20>: nop
0x00000000000101a0 <+22>: ld ra,24(sp)
0x00000000000101a2 <+24>: ld fp,16(sp)
0x00000000000101a4 <+26>: add sp,sp,32
0x00000000000101a6 <+28>: ret
End of assembler dump.
When we are at address 0x101a4 the previous instruction has restored
the frame-pointer, as such GDB's (current) preference for using the
frame-pointer as the frame base address is clearly not going to work.
We need to switch to using the stack-pointer instead.
At address 0x101a6 the previous instruction has restored the
stack-pointer value. Currently GDB will not understand this and so
will still assume the stack has been decreased by 32 bytes in this
function.
My proposed solution is to extend GDB such that GDB will scan the
instructions at the current $pc looking for this pattern:
ld fp,16(sp)
add sp,sp,32
ret
Obviously the immediates can change, but the basic pattern indicates
that the function is in the process of restoring state before
returning. If GDB sees this pattern then GDB can use the inferior's
position within this instruction sequence to help calculate the
correct frame-id.
With this implemented then gdb.base/unwind-on-each-insn.exp now fully
passes.
Obviously what I've implemented is just a heuristic. It's not going
to work for every function. If the compiler reorders the
instructions, or merges the epilogue back into the function body then
GDB is once again going to get the frame-id wrong.
I'm OK with that, we're no worse off that we are right now in that
situation (plus we can always improve the heuristic later).
Remember, this is for debugging code without debug information,
and (in our imagined situation) with more aggressive levels of
optimisation being used. Obviously GDB is going to struggle in these
situations.
My thinking is, lets get something in place now. Then, later, if
possible, we might be able to improve the logic to cover more
situations -- if there's an interest in doing so. But I figure we
need something in place as a starting point.
After this commit gdb.base/unwind-on-each-insn.exp passes with no
failures on RV64.
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Add support to the RISC-V prologue scanner for c.ldsp and c.lwsp
instructions.
This fixes some of the failures in gdb.base/unwind-on-each-insn.exp,
though there are further failures that are not fixed by this commit.
This change started as a wider fix that would address all the failures
in gdb.base/unwind-on-each-insn.exp, however, that wider fix needed
support for the two additional compressed instructions.
When I added support for those two compressed instructions I noticed
that some of the failures in gdb.base/unwind-on-each-insn.exp resolved
themselves!
Here's what's going on:
The reason for the failures is that GDB is trying to build the
frame-id during the last few instructions of the function. These are
the instructions that restore the frame and stack pointers just prior
to the return instruction itself.
By the time we reach the function epilogue the stack offset that we
calculated during the prologue scan is no longer valid, and so we
calculate the wrong frame-id.
However, in the particular case of interest here, the test function
'foo', the function is so simple and short (the empty function) that
GDB's prologue scan could, in theory, scan every instruction of the
function.
I say "could, in theory," because currently GDB stops the prologue
scan early when it hits an unknown instruction. The unknown
instruction happens to be one of the compressed instructions that I'm
adding support for in this commit.
Now that GDB understands the compressed instructions the prologue scan
really does go from the start of the function right up to the current
program counter. As such, GDB sees that the stack frame has been
allocated, and then deallocated, and so builds the correct frame-id.
Of course, most real functions are not as simple as the test function
'foo'. As such, we can't usually rely on scanning right up to the end
of the function -- there are some instructions we always need to stop
at because GDB can't reason about how they change the inferior
state (e.g. a function call). The test function 'bar' is just such an
example.
After this commit, we can now build the frame-id correctly for every
instruction in 'foo', but there are some tests still failing in 'bar'.
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Convert the RISC-V specific debug settings to use the new debug
printing scheme. This updates the following settings:
set/show debug riscv breakpoints
set/show debug riscv gdbarch
set/show debug riscv infcall
set/show debug riscv unwinder
All of these settings now take a boolean rather than an integer, and
all print their output using the new debug scheme.
There should be no visible change for anyone not turning on debug.
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While I was working on the disassembler styling for ARM I noticed that
the whitespace in the cpsie instruction was inconsistent with most of
the other ARM disassembly output, the disassembly for cpsie looks like
this:
cpsie if,#10
notice there's no space before the '#10' immediate, most other ARM
instructions have a space before each operand.
This commit updates the disassembler to add the missing space, and
updates the tests I found that tested this instruction.
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This commit follows on from the following two commits:
commit 80dc83fd0e70f4d522a534bc601df5e05b81d564
Date: Fri Jun 11 11:30:47 2021 +0100
gdb/remote: handle target dying just before a stepi
And:
commit 079f190d4cfc6aa9c934b00a9134bc0fcc172d53
Date: Thu Mar 9 10:45:03 2023 +0100
[gdb/testsuite] Fix gdb.server/server-kill.exp for remote target
The first of these commits fixed an issue in GDB and tried to extend
the gdb.server/server-kill.exp test to cover the GDB fix.
Unfortunately, the changes to gdb.server/server-kill.exp were not
correct, and were causing problems when trying to run with the
remote-gdbserver-on-localhost board file.
The second commit reverts some of the gdb.server/server-kill.exp
changes introduced in the first commit so that the test will now work
correctly with the remote-gdbserver-on-localhost board file.
The second commit is just about GDB's testing infrastructure -- it's
not about the original fix to GDB from the first commit, the actual
GDB change was fine.
While reviewing the second commit I wanted to check that the problem
fixed in the first commit is still being tested by the
gdb.server/server-kill.exp script, so I reverted the change to
breakpoint.c that is the core of the first commit and ran the test
script ..... and saw no failures.
The first commit is about GDB discovering that gdbserver has died
while trying to insert a breakpoint. As soon as GDB spots that
gdbserver is gone we mourn the remote inferior, which ends up deleting
all the breakpoints associated with the remote inferiors. We then
throw an exception which is caught in the insert breakpoints code, and
we try to display an error that includes the breakpoint number
.... but the breakpoint has already been deleted ... and so GDB
crashes.
After digging a little, what I found is that today, when the test does
'stepi' the first thing we end up doing is calculating the frame-id as
part of the stepi logic, it is during this frame-id calculation that
we mourn the remote inferior, delete the breakpoints, and throw an
exception. The exception is caught by the top level interpreter loop,
and so we never try to print the breakpoint number which is what
caused the original crash.
If I add an 'info frame' command to the test script, prior to killing
gdbserver, then now when we 'stepi' GDB already has the frame-id
calculated, and the first thing we do is try to insert the
breakpoints, this will trigger the original bug.
In order to reproduce this experiment you'll need to change a function
in breakpoint.c, like this:
static void
rethrow_on_target_close_error (const gdb_exception &e)
{
return;
}
Then run gdb.server/server-kill.exp with and without this patch. You
should find that without this patch there are zero test failures,
while with this patch there will be one failure like this:
(gdb) PASS: gdb.server/server-kill.exp: test_stepi: info frame
Executing on target: kill -9 4513 (timeout = 300)
builtin_spawn -ignore SIGHUP kill -9 4513
stepi
../../src/gdb/breakpoint.c:2863: internal-error: insert_bp_location: Assertion `bl->owner != nullptr' failed.
A problem internal to GDB has been detected,
further debugging may prove unreliable.
----- Backtrace -----
...
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A potential test failure was introduced with commit:
commit 6bf5f25bb150c0fbcb125e3ee466ba8f9680310b
Date: Wed Mar 8 16:11:30 2023 +0000
gdb/python: make the gdb.unwinder.Unwinder class more robust
In this commit a new test was added, however the expected output
pattern varies depending on which Python version GDB is linked
against.
Older versions of Python result in output like this:
(gdb) python global_test_unwinder.name = "foo"
Traceback (most recent call last):
File "<string>", line 1, in <module>
AttributeError: can't set attribute
Error while executing Python code.
(gdb)
While more recent versions of Python give a similar, but slightly more
verbose error message, like this:
(gdb) python global_test_unwinder.name = "foo"
Traceback (most recent call last):
File "<string>", line 1, in <module>
AttributeError: can't set attribute 'name'
Error while executing Python code.
(gdb)
The test was only accepting the first version of the output. This
commit extends the test pattern so that either version will be
accepted.
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The detection logic for TPIDR2 was implemented incorrectly. Originally
the detection was supposed to be through a ptrace error code, but in reality,
for backwards compatibility, the detection should be based on the size of
the returned iovec.
For instance, if a target supports both TPIDR and TPIDR2, ptrace will return a
iovec size of 16. If a target only supports TPIDR and not TPIDR2, it will
return a iovec size of 8, even if we asked for 16 bytes.
This patch fixes this issue in code that is shared between gdb and gdbserver,
therefore both gdb and gdbserver are fixed.
Tested on AArch64/Linux Ubuntu 20.04.
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A case of a string section ending with an unterminated string. Fix it
by allocating one more byte and making it zero. Also make functions
reading the data return void* so that casts are not needed.
* ecoff.c (READ): Delete type param. Allocate one extra byte
to terminate string sections with a NUL. Adjust invocation.
* elfxx-mips.c (READ): Likewise.
* libbfd-in.h (_bfd_alloc_and_read): Return a void*.
(_bfd_malloc_and_read): Likewise.
* libbfd.h: Regenerate.
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tc-aarch64.c:1473:27: runtime error: left shift of 7 by 30 places
cannot be represented in type 'int'.
* config/tc-aarch64.c (parse_vector_reg_list): Avoid UB left
shift.
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This should sort out some very old FIXMEs in code handling stabs
debug info. Necessary if we are to fuss over freeing up memory before
objdump and objcopy exit. It is of course better from a user
viewpoint to *not* free memory, which takes some time, and leave that
to process exit. The only reason to do so is that having many memory
leaks in binutils/ code tends to hide leaks in bfd/ or opcodes/, which
we should care about.
* budbg.h (parse_stab): Update prototype.
* debug.h (debug_start_source): Update prototype.
* debug.c (debug_start_source): Add name_used. Set if stashed.
* rddbg.c (read_symbol_stabs_debugging_info): Always malloc
stab string passed to parse_stab. Free stab string when
unreferenced.
(read_section_stabs_debugging_info): Likewise, and strings
section contents.
* stabs.c (parse_stab): Add string_used param. Set if string
stashed. Pass to debug_start_source. Realloc file_types
array rather that using malloc. Clarify comment about
debug_make_indirect_type.
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We may have added some abbrevs to the list before hitting an error.
Free the list elements too. free_abbrev_list returns list->next so we
need to init it earlier to avoid an uninitialised memory access.
* dwarf.c (process_abbrev_set): Call free_abbrev_list on errors.
Set list->next earlier.
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I noticed the prefix parameter was unused in print_doc_of_command. And
when removing it, it becomes unused in apropos_cmd.
Change-Id: Id72980b03fe091b22931e6b85945f412b274ed5e
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GDB expected PC should point right after the SVC instruction when the
syscall is active. But some active syscalls keep PC pointing to the SVC
instruction itself.
This leads to a broken backtrace like:
Backtrace stopped: previous frame identical to this frame (corrupt stack?)
#0 0xb6f8681c in pthread_cond_timedwait@@GLIBC_2.4 () from /lib/arm-linux-gnueabihf/libpthread.so.0
#1 0xb6e21f80 in ?? ()
The reason is that .ARM.exidx unwinder gives up if PC does not point
right after the SVC (syscall) instruction. I did not investigate why but
some syscalls will point PC to the SVC instruction itself. This happens
for the "futex" syscall used by pthread_cond_timedwait.
That normally does not matter as ARM prologue unwinder gets called
instead of the .ARM.exidx one. Unfortunately some glibc calls have more
complicated prologue where the GDB unwinder fails to properly determine
the return address (that is in fact an orthogonal GDB bug). I expect it
is due to the "vpush" there in this case but I did not investigate it more:
Dump of assembler code for function pthread_cond_timedwait@@GLIBC_2.4:
0xb6f8757c <+0>: push {r4, r5, r6, r7, r8, r9, r10, r11, lr}
0xb6f87580 <+4>: mov r10, r2
0xb6f87584 <+8>: vpush {d8}
Regression tested on armv7l kernel 5.15.32-v7l+ (Raspbian 11).
Approved-By: Luis Machado <luis.machado@arm.com>
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Linker adds indirect symbols for versioned symbol aliases, which are
created by ".symver foo, foo@FOO", by checking symbol type, value and
section so that references to foo will be replaced by references to
foo@FOO if foo and foo@FOO have the same symbol type, value and section.
But in IR, since all symbols of the same type have the same value and
section, we can't tell if a symbol is an alias of another symbol by
their types, values and sections. We shouldn't add indirect symbols
for versioned symbol aliases in IR.
bfd/
PR ld/30281
* elflink.c (elf_link_add_object_symbols): Don't add indirect
symbols for ".symver foo, foo@FOO" aliases in IR.
ld/
PR ld/30281
* testsuite/ld-plugin/lto.exp: Add PR ld/30281 test.
* testsuite/ld-plugin/pr30281.t: New file.
* testsuite/ld-plugin/pr30281.c: Likewise.
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A recent patch caused my system gcc (Fedora 36, so gcc 12.2.1) to warn
about sym_addr being possibly uninitialized in frame.c. It isn't, but
the compiler can't tell. So, this patch initializes the variable. I
also fixed a formatting buglet that I missed in review.
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With test-case gdb.base/trace-commands.exp and editing off, I run into fails
because multi-line commands are issued using gdb_test_sequence, which
doesn't handle them correctly.
Fix this by using gdb_test instead.
Tested on x86_64-linux.
PR testsuite/30288
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30288
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With test-case gdb.threads/threadapply.exp and editing set to on, we have:
...
(gdb) define remove^M
Type commands for definition of "remove".^M
End with a line saying just "end".^M
>remove-inferiors 3^M
>end^M
(gdb)
...
but with editing set to off, we run into:
...
(gdb) define remove^M
Type commands for definition of "remove".^M
End with a line saying just "end".^M
>remove-inferiors 3^M
end^M
>(gdb) FAIL: gdb.threads/threadapply.exp: thread_set=all: try remove: \
define remove (timeout)
...
The commands are issued by this test:
...
gdb_define_cmd "remove" {
"remove-inferiors 3"
}
...
which does:
- gdb_test_multiple "define remove", followed by
- gdb_test_multiple "remove-inferiors 3\nend".
Proc gdb_test_multiple has special handling for multi-line commands, which
splits it up into subcommands, and for each subcommand issues it and then
waits for the resulting prompt (the secondary prompt ">" for all but the last
subcommand).
However, that doesn't work as expected in this case because the initial
gdb_test_multiple "define remove" fails to match all resulting output, and
consequently the secondary prompt resulting from "define remove" is counted as
if it was the one resulting from "remove-inferiors 3".
Fix this by matching the entire output of "define remove", including the
secondary prompt.
Tested on x86_64-linux.
PR testsuite/30288
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30288
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I noticed that language_demangle shadows the global
"current_language". When I went to fix this, though, I then saw that
language_demangle is only called in two places, and has a comment
saying it should be removed. This patch removes it. Note that the
NULL check in language_demangle is not needed by either of the
existing callers.
Regression tested on x86-64 Fedora 36.
Approved-By: Simon Marchi <simon.marchi@efficios.com>
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