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gdb: remove unused struct call_site_stuff forward declaration

This is unused (and was event when it was introduced). Remove it.

gdb/ChangeLog:

* dwarf2/loc.h (struct call_site_stuff): Remove.

Change-Id: Iaa82cb7cfd9768998553b4c9211aca7529eb402f

gdb, testsuite: Fix mi-var-child-f.exp for Intel compilers.

mi-var-child-f.exp uses array.f as the inferior, which uses an unnamed
main function. This causes false positive fails for Intel compilers, as
they emit the following DWARF:

~~~
0x0000002a: DW_TAG_subprogram
DW_AT_low_pc (0x0000000000404800)
DW_AT_high_pc (0x000000000040484c)
DW_AT_frame_base (DW_OP_reg6 RBP)
DW_AT_linkage_name ("MAIN__")
DW_AT_name ("_unnamed_main$$")
DW_AT_decl_file ("array.f")
DW_AT_decl_line (16)
DW_AT_external (true)
DW_AT_main_subprogram (true)
~~~

The testsuite for fortran uses test_compiler_info to determine a hardcoded
string which is used to run to main and as a testing regex:

~~~
proc fortran_main {} {
if {[test_compiler_info {gcc-4-[012]-*}]
|| [test_compiler_info {gcc-*}]
|| [test_compiler_info {icc-*}] {
return "MAIN__"
} elseif {[test_compiler_info {clang-*}]} {
return "MAIN_"
} else {
return "unknown"
}
}
~~~

GDB however uses DW_AT_name mostly in its output, which fails the regex.
To fix this testcase immediately, I modernized array.f and gave it a named
main. There was no specific reason it was unnamed anyway. Fixing
the testsuite properly is not straightforward. fortran_main and
test_compiler_info would need some changes, which has broader influences.
I might look at this later down the road.

gdb/testsuite/ChangeLog:
2021-06-11 Felix Willgerodt <felix.willgerodt@intel.com>

* gdb.mi/array.f: Convert into...
* gdb.mi/array.f90: ...this.
* gdb.mi/mi-var-child-f.exp: Use array.f90.

Implement Rust raw identifiers

This patch implements Rust raw identifiers in the lexer in gdb. There
was an earlier patch to do this, but the contributor didn't reply to
my email asking whether he had sorted out his copyright assignment.

This is relatively straightforward, but a small test suite addition
was needd to ensure that the new test is skipped on older versions of
rustc -- ones that predate the introduction of raw identifiers.

gdb/ChangeLog
2021-06-11 Tom Tromey <tom@tromey.com>

PR rust/23427
* rust-parse.c (rust_parser::lex_identifier): Handle raw
identifiers.
(rust_lex_tests): Add raw identifier tests.

gdb/testsuite/ChangeLog
2021-06-11 Tom Tromey <tom@tromey.com>

PR rust/23427
* lib/rust-support.exp (rust_compiler_version): New caching proc.
* gdb.rust/rawids.exp: New file.
* gdb.rust/rawids.rs: New file.

x86: Always define TC_PARSE_CONS_EXPRESSION

Always define TC_PARSE_CONS_EXPRESSION to properly wrap constants for
all x86 targets.

* config/tc-i386.c (x86_cons): Handle GOT/PLT relocations only
if needed.
* config/tc-i386.h (TC_PARSE_CONS_EXPRESSION): Always define.

RISC-V: Update the riscv_opts.[rvc|rve] in the riscv_set_arch.

We also need to update the riscv_opts.[rvc|rve] for elf attributes.
Otherwise, the following case will fail,

$ cat cadd.s
.attribute arch, "rv64gc"
c.add a0, a1
$ riscv64-unknown-elf-as cadd.s -o cadd.o
cadd.s: Assembler messages:
cadd.s:2: Error: illegal operands `c.add a0,a1

After applying this patch,

$ riscv64-unknown-elf-as cadd.s -o cadd.o
$ riscv64-unknown-elf-objdump -d cadd.o

cadd.o: file format elf64-littleriscv

Disassembly of section .text:

0000000000000000 <.text>:
0: 952e add a0,a0,a1
...

gas/
* config/tc-riscv.c (riscv_set_arch): Call riscv_set_rvc
and riscv_set_rve both for -march and elf attributes.
(riscv_after_parse_args): Likewise.

readelf info leaks from one object to the next

A number of filedata entries were not cleared. Make sure they are
all cleared out, except the ones needed for archive handling.

* readelf.c (struct filedata): Move archive_file_offset and
archive_file_size earlier.
(free_filedata): Clear using memset.

readelf section reading

This is a followup to git commit 8ff66993e0b5, a patch aimed at
segfaults found invoking readelf multiple times with fuzzed objects.
In that patch I added code to clear more stashed data early in
process_section_headers, along with any stashed section headers. This
patch instead relies on clearing out the stash at the end of
process_object, making sure that process_object doesn't exit early.

The patch also introduces some new wrapper functions.

* readelf.c (GET_ELF_SYMBOLS): Delete. Replace with..
(get_elf_symbols): ..this new function throughout.
(get_32bit_section_headers): Don't free section_headers.
(get_64bit_section_headers): Likewise.
(get_section_headers): New function, use throughout in place of
32bit and 64bit variants.
(get_dynamic_section): Similarly.
(process_section_headers): Don't free filedata memory here.
(get_file_header): Don't get section headers here..
(process_object): ..Read them here instead. Don't exit without
freeing filedata memory.

PR27952, Disallow ET_DYN DF_1_PIE linker input

This patch adds a new elf_tdata flag, is_pie, set during the linker's
open_input_bfds processing. The flag is then used to reject attempts
to link a PIE as if it were a shared library.

bfd/
PR 27952
* elf-bfd.h (struct elf_obj_tdata): Add is_pie.
* elflink.c (elf_link_add_object_symbols): Set is_pie.
ld/
PR 27952
* ldelf.c (ldelf_after_open): Error on input PIEs too.

Automatic date update in version.in

gdb/testsuite: capture GDB tty name in default_gdb_spawn

The TUI test gdb.tui/empty.exp fails with the native-extended-gdbserver
board, and takes a very long time to run due to numerous timeouts. The
symptom, when looking at the logs, is that the TUI windows that we
expect to be resized are not resized. Digging down, I found that GDB
didn't receive any SIGWINCH that should have resulted from
Term::resize's stty calls.

The reason for this is:

- The native-extended-gdbserver overrides gdb_start to first start GDB,
then start GDBserver with --multi, then connect GDB to GDBserver.
This means that two TCL "spawn"s are done, one for GDB and one for
GDBserver.

- The TUI test framework wants to know GDB's TTY name, so it can pass
it to stty, to fake terminal resizes. To do so, it overrides the
spawn built-in proc to capture the tty name from the internals of the
built-in proc. It saves the TTY name to the gdb_spawn_name global
variable.

- Because the native-extended-gdbserver boards starts both GDB and
GDBserver, the final value of gdb_spawn_name is the name of
GDBserver's TTY.

- When the TUI test framework attempts to resize GDB's terminal, it in
fact resizes GDBserver's terminal. So obviously, GDB doesn't get the
SIGWINCH, and we don't get the expected TUI redraw.

Fix that by moving the hack to lib/gdb.exp, overriding the builtin spawn
all the time. The override saves the TTY name in the
last_spawn_tty_name global. The default_gdb_spawn proc then saves it in
the gdb_tty_name global. This way, we specifically capture GDB's TTY
name in gdb_tty_name, not the TTY name of other spawned processes.

Remove tuiterm_env_init and tuiterm_env_finish, since they are now
empty. In turn, the gdb_finish_hooks mechanism is now unused, remove it
as well. It would be easy to add them back if needed.

gdb/ChangeLog:

* lib/gdb.exp (default_gdb_exit): Unset gdb_tty_name.
(spawn_capture_tty_name): New, override builtin spawn.
(default_gdb_spawn): Capture GDB's TTY name.
* lib/tuiterm.exp (tuiterm_spawn): Remove.
(tuiterm_env_init, tuiterm_env_finish): Remove spawn override.
(Term) <resize>: Use new variable name.
(tuiterm_env_init, tuiterm_env_finish): Remove.
(tuiterm_env): Don't call tuiterm_env_init and register
tuiterm_env_finish in gdb_finish_hooks.
(gdb_finish_hooks): Remove.
(gdb_finish): Don't call finish hooks.

Change-Id: Ia5ab74184a52a996416022308f8d0cc523355a78

[gdb/testsuite] Fix timeout in gdb.mi/user-selected-context-sync.exp with gcc-11

When running test-case gdb.mi/user-selected-context-sync.exp with gcc-11, we
get:
...
continue^M
Continuing.^M
FAIL: gdb.mi/user-selected-context-sync.exp: mode=all-stop: test_setup: \
inferior 1: continue to breakpoint: continue thread 1.2 to infinite \
loop breakpoint (timeout)
...

This is a regression since commit aa33ea68330 "testsuite, mi: avoid a clang
bug in 'user-selected-context-sync.exp'", which fixes a similar hang when
using clang.

The source before the commit contains:
...
while (1);
...
and after the commit:
...
int spin = 1;
while (spin);
...

[ FWIW, I've filed a PR gcc/101011 - Inconsistent debug info for "while (1);"
to mention that gcc-11 has different behaviour for these two loops. ]

The problem is that:
- the test-case expects the behaviour that a breakpoint set
on the while line will trigger on every iteration, and
- that is not guaranteed by either version of the loop.

Fix this by using a while loop with a dummy body:
...
volatile int dummy = 0;
while (1)
dummy = !dummy;
...
and setting the breakpoint in the body.

Tested on x86_64-linux with clang 10.0.1, gcc-4.8, gcc 7.5.0 and gcc 11.1.1.

gdb/testsuite/ChangeLog:

2021-06-10 Tom de Vries <tdevries@suse.de>

* gdb.mi/user-selected-context-sync.c (child_sub_function, main):
Rewrite while (1) using dummy loop body.

arm: avoid "shadowing" of glibc function name

Old enough glibc has an (unguarded) declaration of index() in string.h,
which triggers a "shadows a global declaration" warning.

arm: fix array-out-of-bounds upon register parsing error

Despite the comment ahead of the enum explicitly pointing out the need
to also update the corresponding array, 1b8833198c0 ("Add support for
MVE instructions: vcmp and vpt") failed to do so. Oddly enough the issue
appears to be spotted only by rather old gcc (4.3-ish in my case).

x86: suppress LEA optimization in a specific 16-bit case

In 16-bit mode a 16-bit address size LEA with a 16-bit displacement and
a 32-bit destination is shorter to encode than the corresponding MOV.
Commit fe134c656991 ("x86: optimize LEA")'s promise was to only do the
transformation when the encoding size wouldn't grow, i.e. it did go a
little too far. Restrict this specific case of the transformation to
-O2.

[gdb/testsuite] Convert multi-line function call into single line.

After this clang backend patch(https://reviews.llvm.org/D91734), 8 test points
started to FAIL in this test case. As mentioned in this PR, "...this test is
trying to next over a function call; gcc attributes all parameter evaluation
to the function name, while clang will attribute each parameter to its own
location. And when the parameters span across multiple source lines, the
is_stmt heuristic kicks in, so we stop on each line with actual parameters...".

gdb.base/foll-exec.c test file snippet :
. . .
42 execlp (prog, /* tbreak-execlp */
43 prog,
44 "execlp arg1 from foll-exec",
45 (char *) 0);
46
47 printf ("foll-exec is about to execl(execd-prog)...\n");
. . .

Line table: (before clang backend patch for the above code snippet) :
0x000000b0: 84 address += 8, line += 2
0x000000000020196a 42 3 1 0 0
0x000000b1: 08 DW_LNS_const_add_pc (0x0000000000000011)
0x000000b2: 41 address += 3, line += 5
0x000000000020197e 47 3 1 0 0

Line table: (after clang backend patch for the above code snippet) :
0x000000b5: 84 address += 8, line += 2
0x0000000000201958 42 11 1 0 0
0x000000b6: 05 DW_LNS_set_column (4)
0x000000b8: 75 address += 7, line += 1
0x000000000020195f 43 4 1 0 0
0x000000b9: 05 DW_LNS_set_column (3)
0x000000bb: 73 address += 7, line += -1
0x0000000000201966 42 3 1 0 0
0x000000bc: 08 DW_LNS_const_add_pc (0x0000000000000011)
0x000000bd: 4f address += 4, line += 5
0x000000000020197b 47 3 1 0 0

Following 8 test points started to fail after the above clang backend patch.

FAIL: gdb.base/foll-exec.exp: step through execlp call
FAIL: gdb.base/foll-exec.exp: step after execlp call
FAIL: gdb.base/foll-exec.exp: print execd-program/global_i (after execlp)
FAIL: gdb.base/foll-exec.exp: print execd-program/local_j (after execlp)
FAIL: gdb.base/foll-exec.exp: print follow-exec/local_k (after execlp)
FAIL: gdb.base/foll-exec.exp: step through execl call
FAIL: gdb.base/foll-exec.exp: step after execl call
FAIL: gdb.base/foll-exec.exp: print execd-program/local_j (after execl)

As we can note, reason for these new test failures is due to additional
.debug_line entries getting created in case of clang compiler, hence to fix
this issue, test case required either additional next command during
these multi-line function call or combine these multi-line function call into
single line. This PR has taken the latter approach and converted the multi-line
function call into single line in foll-exec.c, thereby there is no change in
.debug_line entries now and test case works as expected.

[gdb/testsuite] Fix gdb.cp/nested-types.exp with check-read1

With check-read1 I occasionally run into:
...
FAIL: gdb.cp/nested-types.exp: ptype S10 (limit = 7) \
// parse failed (timeout)
...
I can trigger this reliably by running check-read1 in conjunction with
stress -c 5.

Fix this by breaking up the regexp in cp_test_ptype_class.

Tested on x86_64-linux.

gdb/testsuite/ChangeLog:

2021-06-10 Tom de Vries <tdevries@suse.de>

* lib/cp-support.exp (cp_test_ptype_class): Break up regexp.
* gdb.cp/nested-types.exp: Remove usage of read1 timeout factor.

[gdb/testsuite] Fix gdb.cp/cplusfuncs.exp with check-read1

When running check-read1, we run into:
...
FAIL: gdb.cp/cplusfuncs.exp: info function for "operator=(" (timeout)
...

Fix this by using using gdb_test_lines in info_func_regexp.

Tested on x86_64-linux.

gdb/testsuite/ChangeLog:

2021-06-10 Tom de Vries <tdevries@suse.de>

* gdb.cp/cplusfuncs.exp (info_func_regexp): Use gdb_test_lines.

Automatic date update in version.in

sim: cleanup obsolete NULL fallback

We require C11 which defines NULL, so drop the inconsistent set of
fallback defines in the codebase.

sim: mn10300: tweak engine halt hook

The hook is a void func, so defining it to 0 triggers warnings,
and isn't really needed.

sim: nrun: tweak init of callback endian

Allow ports to initialize the callback endian if they want. This will
allow delegation of the logic out of common code in the future.

Also switch from the CURRENT_TARGET_BYTE_ORDER macro to the underlying
current_target_byte_order storage since the latter has been setup by
the sim-config module based on the same macros. This will allow the
nrun module to be moved to common building for sharing.

sim: bpf: use CURRENT_TARGET_BYTE_ORDER

Code should be going through this macro rather than accessing the
underlying value directly.

sim: cgen: inline cgen_init logic

This function has done only one thing: post-process command line
settings to see if profiling or tracing has been enabled, and if
so, set the run_fast_p flag in the simulator state. That flag is
only used in one place: to select the fast or slow cgen engine.
By inlining the run_fast_p logic to the one place it's used, we
can delete a good amount of logic specific to cgen ports: both
the call to cgen_init and the conditional simulator state. This
in turn allows us to have a single simulator state struct across
all ports so we can share objects more between them, and makes
the sim_open calls look more consistent.

Update read1 example in gdb/testsuite/README

Tom de Vries noticed that the recent changes to the testsuite's
configury required an update to the README. This patch changes the
text to document the new reality.

2021-06-09 Tom Tromey <tromey@adacore.com>

* README (Example): Update read1 example.

Remove Daniel Jacobwitz from the maintainers list

gdb/testsuite: add some logging in Term::_check_box

I was diagnosing some problem with a TUI test case, which lead me to
improve the logging of _check_box a bit. It did help me, so I think it
would be nice to have it upstream.

gdb/testsuite/ChangeLog:

* lib/tuiterm.exp (Term) <_check_box>: Improve logging.

Change-Id: I887e83c02507d6c59c991e17f795c844ed63bacf

Fix the creation of archives for Sparc Solaris2 targets by eliminating the support for generic SPARC ELF files.

PR 27666
bfd * config.bfd: Do not add the sparc_elf32_vec or sparc_elf64_vec
vectors to Sparc Solaris2 targets.

ld * testsuite/ld-sparc/sparc.exp: Do not run the sparctests or
sparc64tests for Solaris2 targets.

Automatic date update in version.in

Use is/is not to check for None in python code.

While reviewing a patch sent to the mailing list, I noticed there are few
places where python code checks if a variable is 'None' or not by using the
comparison operators '==' and '!='. PEP8[1], which is used as coding standard
in GDB coding standards, recommends using 'is' / 'is not' when comparing to a
singleton such as 'None'.

This patch proposes to change the instances of '== None' by 'is None' and
'!= None' by 'is not None'.

[1] https://www.python.org/dev/peps/pep-0008/

gdb/doc/ChangeLog:

* python.texi (Writing a Pretty-Printer): Use 'is None' instead of
'== None'.

gdb/ChangeLog:

* python/lib/gdb/FrameDecorator.py (FrameDecorator): Use 'is None' instead of
'== None'.
(FrameVars): Use 'is not None' instead of '!= None'.
* python/lib/gdb/command/frame_filters.py (SetFrameFilterPriority): Use 'is None'
instead of '== None' and 'is not None' instead of '!= None'.

gdb/testsuite/ChangeLog:

* gdb.base/premature-dummy-frame-removal.py (TestUnwinder): Use
'is None' instead of '== None' and 'is not None' instead of
'!= None'.
* gdb.python/py-frame-args.py (lookup_function): Same.
* gdb.python/py-framefilter-invalidarg.py (Reverse_Function): Same.
* gdb.python/py-framefilter.py (Reverse_Function): Same.
* gdb.python/py-nested-maps.py (lookup_function): Same.
* gdb.python/py-objfile-script-gdb.py (lookup_function): Same.
* gdb.python/py-prettyprint.py (lookup_function): Same.
* gdb.python/py-section-script.py (lookup_function): Same.
* gdb.python/py-unwind-inline.py (dummy_unwinder): Same.
* gdb.python/python.exp: Same.
* gdb.rust/pp.py (lookup_function): Same.

gdb: try to load libthread_db only after reading all shared libraries when attaching / handling a fork child

When trying to attach to a pthread process on a Linux system with glibc 2.33,
we get:

$ ./gdb -q -nx --data-directory=data-directory -p 1472010
Attaching to process 1472010
[New LWP 1472013]
[New LWP 1472014]
[New LWP 1472015]
Error while reading shared library symbols for /usr/lib/libpthread.so.0:
Cannot find user-level thread for LWP 1472015: generic error
0x00007ffff6d3637f in poll () from /usr/lib/libc.so.6
(gdb)

When attaching to a process (or handling a fork child, an operation very
similar to attaching), GDB reads the shared library list from the
process. For each shared library (if "set auto-solib-add" is on), it
reads its symbols and calls the "new_objfile" observable.

The libthread-db code monitors this observable, and if it sees an
objfile named somewhat like "libpthread.so" go by, it tries to load
libthread_db.so in the GDB process itself. libthread_db knows how to
navigate libpthread's data structures to get information about the
existing threads.

To locate these data structures, libthread_db calls ps_pglobal_lookup
(implemented in proc-service.c), passing in a symbol name and expecting
an address in return.

Before glibc 2.33, libthread_db always asked for symbols found in
libpthread. There was no ordering problem: since we were always trying
to load libthread_db in reaction to processing libpthread (and reading
in its symbols) and libthread_db only asked symbols from libpthread, the
requested symbols could always be found. Starting with glibc 2.33,
libthread_db now asks for a symbol name that can be found in
/lib/ld-linux-x86-64.so.2 (_rtld_global). And the ordering in which GDB
reads the shared libraries from the inferior when attaching is
unfortunate, in that libpthread is processed before ld-linux. So when
loading libthread_db in reaction to processing libpthread, and
libthread_db requests the symbol that is from ld-linux, GDB is not yet
able to supply it.

That problematic symbol lookup happens in the thread_from_lwp function,
when we call td_ta_map_lwp2thr_p, and an exception is thrown at this
point:

#0 0x00007ffff6681012 in __cxxabiv1::__cxa_throw (obj=0x60e000006100, tinfo=0x555560033b50 <typeinfo for gdb_exception_error>, dest=0x55555d9404bc <gdb_exception_error::~gdb_exception_error()>) at /build/gcc/src/gcc/libstdc++-v3/libsupc++/eh_throw.cc:78
#1 0x000055555e5d3734 in throw_it(return_reason, errors, const char *, typedef __va_list_tag __va_list_tag *) (reason=RETURN_ERROR, error=GENERIC_ERROR, fmt=0x55555f0c5360 "Cannot find user-level thread for LWP %ld: %s", ap=0x7fffffffaae0) at /home/simark/src/binutils-gdb/gdbsupport/common-exceptions.cc:200
#2 0x000055555e5d37d4 in throw_verror (error=GENERIC_ERROR, fmt=0x55555f0c5360 "Cannot find user-level thread for LWP %ld: %s", ap=0x7fffffffaae0) at /home/simark/src/binutils-gdb/gdbsupport/common-exceptions.cc:208
#3 0x000055555e0b0ed2 in verror (string=0x55555f0c5360 "Cannot find user-level thread for LWP %ld: %s", args=0x7fffffffaae0) at /home/simark/src/binutils-gdb/gdb/utils.c:171
#4 0x000055555e5e898a in error (fmt=0x55555f0c5360 "Cannot find user-level thread for LWP %ld: %s") at /home/simark/src/binutils-gdb/gdbsupport/errors.cc:43
#5 0x000055555d06b4bc in thread_from_lwp (stopped=0x617000035d80, ptid=...) at /home/simark/src/binutils-gdb/gdb/linux-thread-db.c:418
#6 0x000055555d07040d in try_thread_db_load_1 (info=0x60c000011140) at /home/simark/src/binutils-gdb/gdb/linux-thread-db.c:912
#7 0x000055555d071103 in try_thread_db_load (library=0x55555f0c62a0 "libthread_db.so.1", check_auto_load_safe=false) at /home/simark/src/binutils-gdb/gdb/linux-thread-db.c:1014
#8 0x000055555d072168 in try_thread_db_load_from_sdir () at /home/simark/src/binutils-gdb/gdb/linux-thread-db.c:1091
#9 0x000055555d072d1c in thread_db_load_search () at /home/simark/src/binutils-gdb/gdb/linux-thread-db.c:1146
#10 0x000055555d07365c in thread_db_load () at /home/simark/src/binutils-gdb/gdb/linux-thread-db.c:1203
#11 0x000055555d07373e in check_for_thread_db () at /home/simark/src/binutils-gdb/gdb/linux-thread-db.c:1246
#12 0x000055555d0738ab in thread_db_new_objfile (objfile=0x61300000c0c0) at /home/simark/src/binutils-gdb/gdb/linux-thread-db.c:1275
#13 0x000055555bd10740 in std::__invoke_impl<void, void (*&)(objfile*), objfile*> (__f=@0x616000068d88: 0x55555d073745 <thread_db_new_objfile(objfile*)>) at /usr/include/c++/10.2.0/bits/invoke.h:60
#14 0x000055555bd02096 in std::__invoke_r<void, void (*&)(objfile*), objfile*> (__fn=@0x616000068d88: 0x55555d073745 <thread_db_new_objfile(objfile*)>) at /usr/include/c++/10.2.0/bits/invoke.h:153
#15 0x000055555bce0392 in std::_Function_handler<void (objfile*), void (*)(objfile*)>::_M_invoke(std::_Any_data const&, objfile*&&) (__functor=..., __args#0=@0x7fffffffb4a0: 0x61300000c0c0) at /usr/include/c++/10.2.0/bits/std_function.h:291
#16 0x000055555d3595c0 in std::function<void (objfile*)>::operator()(objfile*) const (this=0x616000068d88, __args#0=0x61300000c0c0) at /usr/include/c++/10.2.0/bits/std_function.h:622
#17 0x000055555d356b7f in gdb::observers::observable<objfile*>::notify (this=0x555566727020 <gdb::observers::new_objfile>, args#0=0x61300000c0c0) at /home/simark/src/binutils-gdb/gdb/../gdbsupport/observable.h:106
#18 0x000055555da3f228 in symbol_file_add_with_addrs (abfd=0x61200001ccc0, name=0x6190000d9090 "/usr/lib/libpthread.so.0", add_flags=..., addrs=0x7fffffffbc10, flags=..., parent=0x0) at /home/simark/src/binutils-gdb/gdb/symfile.c:1131
#19 0x000055555da3f763 in symbol_file_add_from_bfd (abfd=0x61200001ccc0, name=0x6190000d9090 "/usr/lib/libpthread.so.0", add_flags=<error reading variable: Cannot access memory at address 0xffffffffffffffb0>, addrs=0x7fffffffbc10, flags=<error reading variable: Cannot access memory at address 0xffffffffffffffc0>, parent=0x0) at /home/simark/src/binutils-gdb/gdb/symfile.c:1167
#20 0x000055555d95f9fa in solib_read_symbols (so=0x6190000d8e80, flags=...) at /home/simark/src/binutils-gdb/gdb/solib.c:681
#21 0x000055555d96233d in solib_add (pattern=0x0, from_tty=0, readsyms=1) at /home/simark/src/binutils-gdb/gdb/solib.c:987
#22 0x000055555d93646e in enable_break (info=0x608000008f20, from_tty=0) at /home/simark/src/binutils-gdb/gdb/solib-svr4.c:2238
#23 0x000055555d93cfc0 in svr4_solib_create_inferior_hook (from_tty=0) at /home/simark/src/binutils-gdb/gdb/solib-svr4.c:3049
#24 0x000055555d96610d in solib_create_inferior_hook (from_tty=0) at /home/simark/src/binutils-gdb/gdb/solib.c:1195
#25 0x000055555cdee318 in post_create_inferior (from_tty=0) at /home/simark/src/binutils-gdb/gdb/infcmd.c:318
#26 0x000055555ce00e6e in setup_inferior (from_tty=0) at /home/simark/src/binutils-gdb/gdb/infcmd.c:2439
#27 0x000055555ce59c34 in handle_one (event=...) at /home/simark/src/binutils-gdb/gdb/infrun.c:4887
#28 0x000055555ce5cd00 in stop_all_threads () at /home/simark/src/binutils-gdb/gdb/infrun.c:5064
#29 0x000055555ce7f0da in stop_waiting (ecs=0x7fffffffd170) at /home/simark/src/binutils-gdb/gdb/infrun.c:8006
#30 0x000055555ce67f5c in handle_signal_stop (ecs=0x7fffffffd170) at /home/simark/src/binutils-gdb/gdb/infrun.c:6062
#31 0x000055555ce63653 in handle_inferior_event (ecs=0x7fffffffd170) at /home/simark/src/binutils-gdb/gdb/infrun.c:5727
#32 0x000055555ce4f297 in fetch_inferior_event () at /home/simark/src/binutils-gdb/gdb/infrun.c:4105
#33 0x000055555cdbe3bf in inferior_event_handler (event_type=INF_REG_EVENT) at /home/simark/src/binutils-gdb/gdb/inf-loop.c:42
#34 0x000055555d018047 in handle_target_event (error=0, client_data=0x0) at /home/simark/src/binutils-gdb/gdb/linux-nat.c:4060
#35 0x000055555e5ea77e in handle_file_event (file_ptr=0x60600008b1c0, ready_mask=1) at /home/simark/src/binutils-gdb/gdbsupport/event-loop.cc:575
#36 0x000055555e5eb09c in gdb_wait_for_event (block=0) at /home/simark/src/binutils-gdb/gdbsupport/event-loop.cc:701
#37 0x000055555e5e8d19 in gdb_do_one_event () at /home/simark/src/binutils-gdb/gdbsupport/event-loop.cc:212
#38 0x000055555dd6e0d4 in wait_sync_command_done () at /home/simark/src/binutils-gdb/gdb/top.c:528
#39 0x000055555dd6e372 in maybe_wait_sync_command_done (was_sync=0) at /home/simark/src/binutils-gdb/gdb/top.c:545
#40 0x000055555d0ec7c8 in catch_command_errors (command=0x55555ce01bb8 <attach_command(char const*, int)>, arg=0x7fffffffe28d "1472010", from_tty=1, do_bp_actions=false) at /home/simark/src/binutils-gdb/gdb/main.c:452
#41 0x000055555d0f03ad in captured_main_1 (context=0x7fffffffdd10) at /home/simark/src/binutils-gdb/gdb/main.c:1149
#42 0x000055555d0f1239 in captured_main (data=0x7fffffffdd10) at /home/simark/src/binutils-gdb/gdb/main.c:1232
#43 0x000055555d0f1315 in gdb_main (args=0x7fffffffdd10) at /home/simark/src/binutils-gdb/gdb/main.c:1257
#44 0x000055555bb70cf9 in main (argc=7, argv=0x7fffffffde88) at /home/simark/src/binutils-gdb/gdb/gdb.c:32

The exception is caught here:

#0 __cxxabiv1::__cxa_begin_catch (exc_obj_in=0x60e0000060e0) at /build/gcc/src/gcc/libstdc++-v3/libsupc++/eh_catch.cc:84
#1 0x000055555d95fded in solib_read_symbols (so=0x6190000d8e80, flags=...) at /home/simark/src/binutils-gdb/gdb/solib.c:689
#2 0x000055555d96233d in solib_add (pattern=0x0, from_tty=0, readsyms=1) at /home/simark/src/binutils-gdb/gdb/solib.c:987
#3 0x000055555d93646e in enable_break (info=0x608000008f20, from_tty=0) at /home/simark/src/binutils-gdb/gdb/solib-svr4.c:2238
#4 0x000055555d93cfc0 in svr4_solib_create_inferior_hook (from_tty=0) at /home/simark/src/binutils-gdb/gdb/solib-svr4.c:3049
#5 0x000055555d96610d in solib_create_inferior_hook (from_tty=0) at /home/simark/src/binutils-gdb/gdb/solib.c:1195
#6 0x000055555cdee318 in post_create_inferior (from_tty=0) at /home/simark/src/binutils-gdb/gdb/infcmd.c:318
#7 0x000055555ce00e6e in setup_inferior (from_tty=0) at /home/simark/src/binutils-gdb/gdb/infcmd.c:2439
#8 0x000055555ce59c34 in handle_one (event=...) at /home/simark/src/binutils-gdb/gdb/infrun.c:4887
#9 0x000055555ce5cd00 in stop_all_threads () at /home/simark/src/binutils-gdb/gdb/infrun.c:5064
#10 0x000055555ce7f0da in stop_waiting (ecs=0x7fffffffd170) at /home/simark/src/binutils-gdb/gdb/infrun.c:8006
#11 0x000055555ce67f5c in handle_signal_stop (ecs=0x7fffffffd170) at /home/simark/src/binutils-gdb/gdb/infrun.c:6062
#12 0x000055555ce63653 in handle_inferior_event (ecs=0x7fffffffd170) at /home/simark/src/binutils-gdb/gdb/infrun.c:5727
#13 0x000055555ce4f297 in fetch_inferior_event () at /home/simark/src/binutils-gdb/gdb/infrun.c:4105
#14 0x000055555cdbe3bf in inferior_event_handler (event_type=INF_REG_EVENT) at /home/simark/src/binutils-gdb/gdb/inf-loop.c:42
#15 0x000055555d018047 in handle_target_event (error=0, client_data=0x0) at /home/simark/src/binutils-gdb/gdb/linux-nat.c:4060
#16 0x000055555e5ea77e in handle_file_event (file_ptr=0x60600008b1c0, ready_mask=1) at /home/simark/src/binutils-gdb/gdbsupport/event-loop.cc:575
#17 0x000055555e5eb09c in gdb_wait_for_event (block=0) at /home/simark/src/binutils-gdb/gdbsupport/event-loop.cc:701
#18 0x000055555e5e8d19 in gdb_do_one_event () at /home/simark/src/binutils-gdb/gdbsupport/event-loop.cc:212
#19 0x000055555dd6e0d4 in wait_sync_command_done () at /home/simark/src/binutils-gdb/gdb/top.c:528
#20 0x000055555dd6e372 in maybe_wait_sync_command_done (was_sync=0) at /home/simark/src/binutils-gdb/gdb/top.c:545
#21 0x000055555d0ec7c8 in catch_command_errors (command=0x55555ce01bb8 <attach_command(char const*, int)>, arg=0x7fffffffe28d "1472010", from_tty=1, do_bp_actions=false) at /home/simark/src/binutils-gdb/gdb/main.c:452
#22 0x000055555d0f03ad in captured_main_1 (context=0x7fffffffdd10) at /home/simark/src/binutils-gdb/gdb/main.c:1149
#23 0x000055555d0f1239 in captured_main (data=0x7fffffffdd10) at /home/simark/src/binutils-gdb/gdb/main.c:1232
#24 0x000055555d0f1315 in gdb_main (args=0x7fffffffdd10) at /home/simark/src/binutils-gdb/gdb/main.c:1257
#25 0x000055555bb70cf9 in main (argc=7, argv=0x7fffffffde88) at /home/simark/src/binutils-gdb/gdb/gdb.c:32

Catching the exception at this point means that the thread_db_info
object for this inferior will be left in place, despite the failure to
load libthread_db. This means that there won't be further attempts at
loading libthread_db, because thread_db_load will think that
libthread_db is already loaded for this inferior and will always exit
early. To fix this, add a try/catch around calling try_thread_db_load_1
in try_thread_db_load, such that if some exception is thrown while
trying to load libthread_db, we reset / delete the thread_db_info for
that inferior. That alone makes attach work fine again, because
check_for_thread_db is called again in the thread_db_inferior_created
observer (that happens after we learned about all shared libraries and
their symbols), and libthread_db is successfully loaded then.

When attaching, I think that the inferior_created observer is a good
place to try to load libthread_db: it is called once everything has
stabilized, when we learned about all shared libraries.

The only problem then is that when we first try (and fail) to load
libthread_db, in reaction to learning about libpthread, we show this
warning:

warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.

This is misleading, because we do succeed in loading it later. So when
attaching, I think we shouldn't try to load libthread_db in reaction to
the new_objfile events, we should wait until we have learned about all
shared libraries (using the inferior_created observable). To do so, add
an `in_initial_library_scan` flag to struct inferior. This flag is used
to postpone loading libthread_db if we are attaching or handling a fork
child.

When debugging remotely with GDBserver, the same problem happens, except
that the qSymbol mechanism (allowing the remote side to ask GDB for
symbols values) is involved. The fix there is the same idea, we make
GDB wait until all shared libraries and their symbols are known before
sending out a qSymbol packet. This way, we never present the remote
side a state where libpthread.so's symbols are known but ld-linux's
symbols aren't.

gdb/ChangeLog:

* inferior.h (class inferior) <in_initial_library_scan>: New.
* infcmd.c (post_create_inferior): Set in_initial_library_scan.
* infrun.c (follow_fork_inferior): Likewise.
* linux-thread-db.c (try_thread_db_load): Catch exception thrown
by try_thread_db_load_1
(thread_db_load): Return early if in_initial_library_scan is
set.
* remote.c (remote_new_objfile): Return early if
in_initial_library_scan is set.

Change-Id: I7a279836cfbb2b362b4fde11b196b4aab82f5efb