[lldb][test] Fix vCont-threads/main.cp for -std=c++11

Remove uses of ATOMIC_VAR_INIT

ATOMIC_VAR_INIT has a trivial definition `#define ATOMIC_VAR_INIT(value) (value)`,
is deprecated in C17/C++20, and will be removed in newer standards.

Reland "[lldb] [test] Improve stability of llgs vCont-threads tests"

Perform a major refactoring of vCont-threads tests in order to attempt
to improve their stability and performance.

Split test_vC

Reland "[lldb] [test] Improve stability of llgs vCont-threads tests"

Perform a major refactoring of vCont-threads tests in order to attempt
to improve their stability and performance.

Split test_vCont_run_subset_of_threads() into smaller test cases,
and split the whole suite into two files: one for signal-related tests,
the running-subset-of tests.

Eliminate output_match checks entirely, as they are fragile to
fragmentation of output. Instead, for the initial thread list capture
raise an explicit SIGINT from inside the test program, and for
the remaining output let the test program run until exit, and check all
the captured output afterwards.

For resume tests, capture the LLDB's thread view before and after
starting new threads in order to determine the IDs corresponding
to subthreads rather than relying on program output for that.

Add a mutex for output to guarantee serialization. A barrier is used
to guarantee that all threads start before SIGINT, and an atomic bool
is used to delay prints from happening until after SIGINT.

Call std::this_thread::yield() to reduce the risk of one of the threads
not being run.

This fixes the test hangs on FreeBSD. Hopefully, it will also fix all
the flakiness on buildbots.

Thanks to Pavel Labath for figuring out why the original version did not
work on Debian.

Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.llvm.org/D129012

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Revert "[lldb] [test] Improve stability of llgs vCont-threads tests"

This reverts commit 86e472317c8fd9309b76c32ca55fcdeaf63f853b.
It breaks Debian buildbot, for some reason.

[lldb] [test] Improve stability of llgs vCont-threads tests

Perform a major refactoring of vCont-threads tests in order to attempt
to improve their stability and performance.

Split test_vCont_run_s

[lldb] [test] Improve stability of llgs vCont-threads tests

Perform a major refactoring of vCont-threads tests in order to attempt
to improve their stability and performance.

Split test_vCont_run_subset_of_threads() into smaller test cases,
and split the whole suite into two files: one for signal-related tests,
the running-subset-of tests.

Eliminate output_match checks entirely, as they are fragile to
fragmentation of output. Instead, for the initial thread list capture
raise an explicit SIGSTOP from inside the test program, and for
the remaining output let the test program run until exit, and check all
the captured output afterwards.

For resume tests, capture the LLDB's thread view before and after
starting new threads in order to determine the IDs corresponding
to subthreads rather than relying on program output for that.

Add a mutex for output to guarantee serialization. A barrier is used
to guarantee that all threads start before SIGSTOP, and an atomic bool
is used to delay prints from happening until after SIGSTOP.

Call std::this_thread::yield() to reduce the risk of one of the threads
not being run.

This fixes the test hangs on FreeBSD. Hopefully, it will also fix all
the flakiness on buildbots.

Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.llvm.org/D129012

show more ...

[lldb] [llgs] Support "t" vCont action

Implement support for the "t" action that is used to stop a thread.
Normally this action is used only in non-stop mode. However, there's
no technical reason w

[lldb] [llgs] Support "t" vCont action

Implement support for the "t" action that is used to stop a thread.
Normally this action is used only in non-stop mode. However, there's
no technical reason why it couldn't be also used in all-stop mode,
e.g. to express "resume all threads except ..." (`t:...;c`).

While at it, add a more complete test for vCont correctly resuming
a subset of program's threads.

Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.llvm.org/D126983

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[lldb] More missing includes in TestGdbRemote_vContThreads

[lldb] Add missing include in TestGdbRemote_vContThreads test

should fix the arm builtbots.

[lldb/test] Deflake TestGdbRemote_vContThreads even more

This patch fixes an issue, where if the thread has a signal blocked when
we try to inject it into the process (via vCont), then instead of
ex

[lldb/test] Deflake TestGdbRemote_vContThreads even more

This patch fixes an issue, where if the thread has a signal blocked when
we try to inject it into the process (via vCont), then instead of
executing straight away, the injected signal will trigger another stop
when the thread unblocks the signal.

As (linux) threads start their life with SIGUSR1 (among others)
disabled, and only enable it during initialization, injecting the signal
during this window did not behave as expected. The fix is to change the
test to ensure the signal gets injected with the signal unblocked.

The simplest way to do this was to write a dedicated inferior for this
test. I also created a new header to factor out the function retrieving
the (os-specific) thread id.

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