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Merged
merged 1 commit into from
Feb 25, 2025
Merged

[libc++] Don't try to wait on a thread that hasn't started in std::async #125433

merged 1 commit into from
Feb 25, 2025

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philnik777
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If the creation of a thread fails, this causes an idle loop that will never end because the thread wasn't started in the first place.

Fixes #125428

@philnik777 philnik777 requested a review from a team as a code owner February 2, 2025 21:08
@llvmbot llvmbot added the libc++ libc++ C++ Standard Library. Not GNU libstdc++. Not libc++abi. label Feb 2, 2025
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llvmbot commented Feb 2, 2025

@llvm/pr-subscribers-libcxx

Author: Nikolas Klauser (philnik777)

Changes

If the creation of a thread fails, this causes an idle loop that will never end because the thread wasn't started in the first place.

Fixes #125428

Full diff: https://github.com/llvm/llvm-project/pull/125433.diff

2 Files Affected:

  • (modified) libcxx/include/future (+4-2)
  • (added) libcxx/test/std/thread/futures/futures.async/thread_create_failure.pass.cpp (+46)
diff --git a/libcxx/include/future b/libcxx/include/future
index db1f624244b8f77..514d4c3d633d6cf 100644
--- a/libcxx/include/future
+++ b/libcxx/include/future
@@ -865,7 +865,8 @@ void __async_assoc_state<_Rp, _Fp>::__execute() {
 
 template <class _Rp, class _Fp>
 void __async_assoc_state<_Rp, _Fp>::__on_zero_shared() _NOEXCEPT {
-  this->wait();
+  if (base::__state_ & base::__constructed)
+    this->wait();
   base::__on_zero_shared();
 }
 
@@ -902,7 +903,8 @@ void __async_assoc_state<void, _Fp>::__execute() {
 
 template <class _Fp>
 void __async_assoc_state<void, _Fp>::__on_zero_shared() _NOEXCEPT {
-  this->wait();
+  if (base::__state_ & base::__constructed)
+    this->wait();
   base::__on_zero_shared();
 }
 
diff --git a/libcxx/test/std/thread/futures/futures.async/thread_create_failure.pass.cpp b/libcxx/test/std/thread/futures/futures.async/thread_create_failure.pass.cpp
new file mode 100644
index 000000000000000..ac5db590dbd8d1d
--- /dev/null
+++ b/libcxx/test/std/thread/futures/futures.async/thread_create_failure.pass.cpp
@@ -0,0 +1,46 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// UNSUPPORTED: no-threads
+
+// There is no way to limit the number of threads on windows
+// UNSUPPORTED: msvc
+
+#include <cassert>
+#include <future>
+#include <system_error>
+
+#if __has_include(<sys/resource.h>)
+#  include <sys/resource.h>
+#  ifdef RLIMIT_NPROC
+void force_thread_creation_failure() {
+  rlimit lim = {1, 1};
+  setrlimit(RLIMIT_NPROC, &lim);
+}
+#  else
+#    error "No known way to force only one thread being available"
+#  endif
+#else
+#  error "No known way to force only one thread being available"
+#endif
+
+int main() {
+  force_thread_creation_failure();
+
+  try {
+    auto fut = std::async(std::launch::async, [] { return 1; });
+    assert(false);
+  } catch (const std::system_error&) {
+  }
+
+  try {
+    auto fut = std::async(std::launch::async, [] { return; });
+    assert(false);
+  } catch (const std::system_error&) {
+  }
+}

@philnik777 philnik777 force-pushed the fix_async_thread_create_failure branch from 5504050 to d1944d4 Compare February 4, 2025 13:05
ldionne
ldionne requested changes Feb 19, 2025
View reviewed changes
@philnik777 philnik777 force-pushed the fix_async_thread_create_failure branch 2 times, most recently from ab20aa6 to b20ce83 Compare February 20, 2025 08:32
@philnik777 philnik777 force-pushed the fix_async_thread_create_failure branch from b20ce83 to cc88f55 Compare February 22, 2025 09:54
@philnik777 philnik777 force-pushed the fix_async_thread_create_failure branch from cc88f55 to 16cec3e Compare February 22, 2025 21:34
@philnik777 philnik777 merged commit 11766a4 into llvm:main Feb 25, 2025
77 of 81 checks passed
@philnik777 philnik777 deleted the fix_async_thread_create_failure branch February 25, 2025 12:33
@slotosch
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Thank you very much for this quick fix

@philnik777
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Thank you very much for this quick fix

You're welcome!

@thurstond thurstond mentioned this pull request Feb 25, 2025
Merged
thurstond added a commit to thurstond/llvm-project that referenced this pull request Feb 25, 2025
@thurstond
Exclude hwasan from thread_create_failure.pass.cpp
6661034 
Fixes hwasan buildbot failure
(https://lab.llvm.org/buildbot/#/builders/55/builds/7536/steps/10/logs/stdio) introduced in llvm#125433 by excluding this test for hwasan, similar to the existing exclusion of asan.
thurstond added a commit that referenced this pull request Feb 25, 2025
@thurstond
Exclude hwasan from thread_create_failure.pass.cpp (#128768)
5e4938a 
Fixes hwasan buildbot failure

(https://lab.llvm.org/buildbot/#/builders/55/builds/7536/steps/10/logs/stdio)
introduced in #125433 by
excluding this test for hwasan, similar to the existing exclusion of
asan.
llvm-sync bot pushed a commit to arm/arm-toolchain that referenced this pull request Feb 25, 2025
@thurstond @github-actions
Automerge: Exclude hwasan from thread_create_failure.pass.cpp (#128768)
4710e82 
Fixes hwasan buildbot failure

(https://lab.llvm.org/buildbot/#/builders/55/builds/7536/steps/10/logs/stdio)
introduced in llvm/llvm-project#125433 by
excluding this test for hwasan, similar to the existing exclusion of
asan.
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mysterymath commented Feb 25, 2025 •
edited
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This looks like the only plausible change in a blamelist for a Fuchsia test regression when trying to roll HEAD clang:
https://issuetracker.google.com/399181046

It includes the error libc++abi: terminating due to uncaught exception of type std::__2::future_error: Operation not permitted on an object without an associated state..

If this is the culprit, it's either an issue with this change generally or with our usage of std::future. Does it seem plausible that this change could change behavior in a breaky way? Regardless, I can start reading up on the context for this change and looking into the error on our side.

@philnik777
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I guess it's possible if somehow the __constructed bit isn't set but should be.

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A bit more information; I was able to pull this stack trace:

17:30:02.376092 test223:    #3    0x00000041d5f3ab5e in std::__terminate(std::terminate_handler) libcxxabi/src/cxa_handlers.cpp:59 <libc++abi.so.1>+0x33b5e from CFI
17:30:02.376097 test223:    #4    0x00000041d5f3df06 in __cxxabiv1::failed_throw(__cxxabiv1::__cxa_exception*) libcxxabi/src/cxa_exception.cpp:152 <libc++abi.so.1>+0x36f06 from CFI
17:30:02.376101 test223:    #5    0x00000041d5f3def0 in __cxa_throw(void*, std::type_info*, void (*)(void*)) libcxxabi/src/cxa_exception.cpp:299 <libc++abi.so.1>+0x36ef0 from CFI
17:30:02.376105 test223:    #6    0x000003f1a252333e in std::__2::__throw_future_error(std::__2::future_errc) /b/s/w/ir/x/w/llvm_build/include/c++/v1/future:516 <libc++.so.2>+0xa033e from CFI
17:30:02.376128 test223:    #7    0x000003f1a252390b in std::__2::__assoc_sub_state::__execute(std::__2::__assoc_sub_state*) libcxx/src/future.cpp:125 <libc++.so.2>+0xa090b from CFI
17:30:02.376133 test223:    #8    0x0000003a24ba54e5 in std::__2::__invoke<void(std::__2::__async_assoc_state<void, std::__2::__async_func<(lambda at../../sdk/lib/async/test/executor_tests.cc:83:44)>>::*)(), std::__2::__async_assoc_state<void, std::__2::__async_func<(lambda at../../sdk/lib/async/test/executor_tests.cc:83:44)>>*, void>(void (std::__2::__async_assoc_state<void, std::__2::__async_func<(lambda at ../../sdk/lib/async/test/executor_tests.cc:83:44)> >::*)(std::__2::__async_assoc_state<void, std::__2::__async_func<(lambda at ../../sdk/lib/async/test/executor_tests.cc:83:44)> >*)&&, std::__2::__async_assoc_state<void, std::__2::__async_func<(lambda at ../../sdk/lib/async/test/executor_tests.cc:83:44)> >*&&) ../../prebuilt/third_party/clang/custom/include/c++/v1/__type_traits/invoke.h:147 <<VMO#3004932=blob-5dfe767c>>+0x4e4e5 from CFI
17:30:02.376137 test223:    #9    0x0000003a24ba543e in std::__2::__thread_execute<std::__2::unique_ptr<std::__2::__thread_struct, std::__2::default_delete<std::__2::__thread_struct>>, void(std::__2::__async_assoc_state<void, std::__2::__async_func<(lambda at../../sdk/lib/async/test/executor_tests.cc:83:44)>>::*)(), std::__2::__async_assoc_state<void, std::__2::__async_func<(lambda at../../sdk/lib/async/test/executor_tests.cc:83:44)>>*, 2UL>(std::__2::tuple<std::__2::unique_ptr<std::__2::__thread_struct, std::__2::default_delete<std::__2::__thread_struct> >, void (std::__2::__async_assoc_state<void, std::__2::__async_func<(lambda at ../../sdk/lib/async/test/executor_tests.cc:83:44)> >::*)(), std::__2::__async_assoc_state<void, std::__2::__async_func<(lambda at ../../sdk/lib/async/test/executor_tests.cc:83:44)> > *>&, std::__2::__tuple_indices<2UL>) ../../prebuilt/third_party/clang/custom/include/c++/v1/__thread/thread.h:199 <<VMO#3004932=blob-5dfe767c>>+0x4e43e from CFI
17:30:02.376141 test223:    #10   0x0000003a24ba523c in std::__2::__thread_proxy<std::__2::tuple<std::__2::unique_ptr<std::__2::__thread_struct, std::__2::default_delete<std::__2::__thread_struct>>, void(std::__2::__async_assoc_state<void, std::__2::__async_func<(lambda at../../sdk/lib/async/test/executor_tests.cc:83:44)>>::*)(), std::__2::__async_assoc_state<void, std::__2::__async_func<(lambda at../../sdk/lib/async/test/executor_tests.cc:83:44)>>*>>(void*) ../../prebuilt/third_party/clang/custom/include/c++/v1/__thread/thread.h:208 <<VMO#3004932=blob-5dfe767c>>+0x4e23c from CFI

@kadircet kadircet mentioned this pull request Mar 6, 2025
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kadircet commented Mar 6, 2025

hi folks, we've also started seeing some use-after-free issues after this patch in clangd. I've sent out https://github.com/llvm/llvm-project/pull/130077/files to stop the bleeding for now, but I feel like there's something off with this change.

Pattern in clangd looks like:

void bar() {
   std::future<...> x = std::async(std::launch::async, [some_state]{ // uses some_state; });
   // destruct x, don't block explicitly for completion of async task. relying on 
}

after this patch destructor doesn't block on completion of async task in the future, as a result we free some_state and hit use after free as the execution of the async task makes progress.

so this code is relying on:

I am not an expert here, so my reading of the standard might be wrong hence I am leaving the final call to you folks. but I feel like this is a rather common pattern and changing behavior here might yield breakages in existing code.

Moreover patch description mentions Don't try to wait on a thread that hasn't started, that's clearly not the case here. we've got a task that's already running hence I feel like this is not an intended affect of this patch (LMK if I can provide more info).

full asan failure 
=================================================================
==3188==ERROR: AddressSanitizer: heap-use-after-free on address 0x7c72c1ac8c40 at pc 0x7f5736d7521b bp 0x7b52a9c39dc0 sp 0x7b52a9c39db8
READ of size 8 at 0x7c72c1ac8c40 thread T49
    #0 0x7f5736d7521a in __invoke<void (std::__u::__async_assoc_state<std::__u::pair<bool, clang::clangd::SymbolSlab>, std::__u::__async_func<(lambda at [third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.h:130](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.h?l=130&ws=eaeltsin/6692&snapshot=611):7), llvm::unique_function<std::__u::pair<bool, clang::clangd::SymbolSlab> ()>, clang::clangd::Context> >::*)(), std::__u::__async_assoc_state<std::__u::pair<bool, clang::clangd::SymbolSlab>, std::__u::__async_func<(lambda at [third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.h:130](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.h?l=130&ws=eaeltsin/6692&snapshot=611):7), llvm::unique_function<std::__u::pair<bool, clang::clangd::SymbolSlab> ()>, clang::clangd::Context> > *, void> [third_party/crosstool/v18/llvm_unstable/src/libcxx/include/__type_traits/invoke.h:147](https://cs.corp.google.com/piper///depot/google3/third_party/crosstool/v18/llvm_unstable/src/libcxx/include/__type_traits/invoke.h?l=147&ws=eaeltsin/6692&snapshot=611):25
    #1 0x7f5736d7521a in __thread_execute<std::__u::unique_ptr<std::__u::__thread_struct, std::__u::default_delete<std::__u::__thread_struct> >, void (std::__u::__async_assoc_state<std::__u::pair<bool, clang::clangd::SymbolSlab>, std::__u::__async_func<(lambda at [third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.h:130](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.h?l=130&ws=eaeltsin/6692&snapshot=611):7), llvm::unique_function<std::__u::pair<bool, clang::clangd::SymbolSlab> ()>, clang::clangd::Context> >::*)(), std::__u::__async_assoc_state<std::__u::pair<bool, clang::clangd::SymbolSlab>, std::__u::__async_func<(lambda at [third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.h:130](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.h?l=130&ws=eaeltsin/6692&snapshot=611):7), llvm::unique_function<std::__u::pair<bool, clang::clangd::SymbolSlab> ()>, clang::clangd::Context> > *, 2UL> [third_party/crosstool/v18/llvm_unstable/src/libcxx/include/__thread/thread.h:200](https://cs.corp.google.com/piper///depot/google3/third_party/crosstool/v18/llvm_unstable/src/libcxx/include/__thread/thread.h?l=200&ws=eaeltsin/6692&snapshot=611):3
    #2 0x7f5736d7521a in void* std::__u::__thread_proxy<std::__u::tuple<std::__u::unique_ptr<std::__u::__thread_struct, std::__u::default_delete<std::__u::__thread_struct>>, void (std::__u::__async_assoc_state<std::__u::pair<bool, clang::clangd::SymbolSlab>, std::__u::__async_func<std::__u::future<std::__u::pair<bool, clang::clangd::SymbolSlab>> clang::clangd::runAsync<std::__u::pair<bool, clang::clangd::SymbolSlab>>(llvm::unique_function<std::__u::pair<bool, clang::clangd::SymbolSlab> ()>)::'lambda'(llvm::unique_function<std::__u::pair<bool, clang::clangd::SymbolSlab> ()>&&, clang::clangd::Context), llvm::unique_function<std::__u::pair<bool, clang::clangd::SymbolSlab> ()>, clang::clangd::Context>>::*)(), std::__u::__async_assoc_state<std::__u::pair<bool, clang::clangd::SymbolSlab>, std::__u::__async_func<std::__u::future<std::__u::pair<bool, clang::clangd::SymbolSlab>> clang::clangd::runAsync<std::__u::pair<bool, clang::clangd::SymbolSlab>>(llvm::unique_function<std::__u::pair<bool, clang::clangd::SymbolSlab> ()>)::'lambda'(llvm::unique_function<std::__u::pair<bool, clang::clangd::SymbolSlab> ()>&&, clang::clangd::Context), llvm::unique_function<std::__u::pair<bool, clang::clangd::SymbolSlab> ()>, clang::clangd::Context>>*>>(void*) [third_party/crosstool/v18/llvm_unstable/src/libcxx/include/__thread/thread.h:209](https://cs.corp.google.com/piper///depot/google3/third_party/crosstool/v18/llvm_unstable/src/libcxx/include/__thread/thread.h?l=209&ws=eaeltsin/6692&snapshot=611):3
    #3 0x55a92182aef0 in asan_thread_start(void*) [third_party/llvm/llvm-project/compiler-rt/lib/asan/asan_interceptors.cpp:239](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/compiler-rt/lib/asan/asan_interceptors.cpp?l=239&ws=eaeltsin/6692&snapshot=611):28
    #4 0x7f5726b477da in start_thread (/usr/grte/v5/lib64/libpthread.so.0+0xb7da) (BuildId: b431ea3122d3e21a60bfe317db5010e3)

0x7c72c1ac8c40 is located 0 bytes inside of 296-byte region [0x7c72c1ac8c40,0x7c72c1ac8d68)
freed by thread T48 (task:foo.cpp) here:
    #0 0x55a921868842 in operator delete(void*, unsigned long) [third_party/llvm/llvm-project/compiler-rt/lib/asan/asan_new_delete.cpp:155](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/compiler-rt/lib/asan/asan_new_delete.cpp?l=155&ws=eaeltsin/6692&snapshot=611):3
    #1 0x7f5736d74a37 in std::__u::__async_assoc_state<std::__u::pair<bool, clang::clangd::SymbolSlab>, std::__u::__async_func<std::__u::future<std::__u::pair<bool, clang::clangd::SymbolSlab>> clang::clangd::runAsync<std::__u::pair<bool, clang::clangd::SymbolSlab>>(llvm::unique_function<std::__u::pair<bool, clang::clangd::SymbolSlab> ()>)::'lambda'(llvm::unique_function<std::__u::pair<bool, clang::clangd::SymbolSlab> ()>&&, clang::clangd::Context), llvm::unique_function<std::__u::pair<bool, clang::clangd::SymbolSlab> ()>, clang::clangd::Context>>::~__async_assoc_state() third_party/crosstool/v18/llvm_unstable/src/libcxx/include/future:837:7
    #2 0x7f5736d74ab9 in __on_zero_shared third_party/crosstool/v18/llvm_unstable/src/libcxx/include/future:616:3
    #3 0x7f5736d74ab9 in std::__u::__async_assoc_state<std::__u::pair<bool, clang::clangd::SymbolSlab>, std::__u::__async_func<std::__u::future<std::__u::pair<bool, clang::clangd::SymbolSlab>> clang::clangd::runAsync<std::__u::pair<bool, clang::clangd::SymbolSlab>>(llvm::unique_function<std::__u::pair<bool, clang::clangd::SymbolSlab> ()>)::'lambda'(llvm::unique_function<std::__u::pair<bool, clang::clangd::SymbolSlab> ()>&&, clang::clangd::Context), llvm::unique_function<std::__u::pair<bool, clang::clangd::SymbolSlab> ()>, clang::clangd::Context>>::__on_zero_shared() third_party/crosstool/v18/llvm_unstable/src/libcxx/include/future:870:9
    #4 0x7f5736d37029 in __release_shared [third_party/crosstool/v18/llvm_unstable/src/libcxx/include/__memory/shared_count.h:92](https://cs.corp.google.com/piper///depot/google3/third_party/crosstool/v18/llvm_unstable/src/libcxx/include/__memory/shared_count.h?l=92&ws=eaeltsin/6692&snapshot=611):7
    #5 0x7f5736d37029 in ~future third_party/crosstool/v18/llvm_unstable/src/libcxx/include/future:987:15
    #6 0x7f5736d37029 in ~SpeculativeFuzzyFind [third_party/llvm/llvm-project/clang-tools-extra/clangd/CodeComplete.h:269](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang-tools-extra/clangd/CodeComplete.h?l=269&ws=eaeltsin/6692&snapshot=611):8
    #7 0x7f5736d37029 in std::__u::__optional_destruct_base<clang::clangd::SpeculativeFuzzyFind, false>::~__optional_destruct_base() third_party/crosstool/v18/llvm_unstable/src/libcxx/include/optional:300:15
    #8 0x7f5736d36967 in operator() [third_party/llvm/llvm-project/clang-tools-extra/clangd/ClangdServer.cpp:475](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang-tools-extra/clangd/ClangdServer.cpp?l=475&ws=eaeltsin/6692&snapshot=611):3
    #9 0x7f5736d36967 in void llvm::detail::UniqueFunctionBase<void, llvm::Expected<clang::clangd::InputsAndPreamble>>::CallImpl<clang::clangd::ClangdServer::codeComplete(llvm::StringRef, clang::clangd::Position, clang::clangd::CodeCompleteOptions const&, llvm::unique_function<void (llvm::Expected<clang::clangd::CodeCompleteResult>)>)::$_0>(void*, llvm::Expected<clang::clangd::InputsAndPreamble>&) [third_party/llvm/llvm-project/llvm/include/llvm/ADT/FunctionExtras.h:222](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/llvm/include/llvm/ADT/FunctionExtras.h?l=222&ws=eaeltsin/6692&snapshot=611):12
    #10 0x7f57370b022c in operator() [third_party/llvm/llvm-project/llvm/include/llvm/ADT/FunctionExtras.h:387](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/llvm/include/llvm/ADT/FunctionExtras.h?l=387&ws=eaeltsin/6692&snapshot=611):12
    #11 0x7f57370b022c in operator() [third_party/llvm/llvm-project/clang-tools-extra/clangd/TUScheduler.cpp:1811](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang-tools-extra/clangd/TUScheduler.cpp?l=1811&ws=eaeltsin/6692&snapshot=611):5
    #12 0x7f57370b022c in void llvm::detail::UniqueFunctionBase<void>::CallImpl<clang::clangd::TUScheduler::runWithPreamble(llvm::StringRef, llvm::StringRef, clang::clangd::TUScheduler::PreambleConsistency, llvm::unique_function<void (llvm::Expected<clang::clangd::InputsAndPreamble>)>)::$_0>(void*) [third_party/llvm/llvm-project/llvm/include/llvm/ADT/FunctionExtras.h:222](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/llvm/include/llvm/ADT/FunctionExtras.h?l=222&ws=eaeltsin/6692&snapshot=611):12
    #13 0x7f5722f1eeaf in operator() [third_party/llvm/llvm-project/llvm/include/llvm/ADT/FunctionExtras.h:387](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/llvm/include/llvm/ADT/FunctionExtras.h?l=387&ws=eaeltsin/6692&snapshot=611):12
    #14 0x7f5722f1eeaf in operator() [third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.cpp:101](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.cpp?l=101&ws=eaeltsin/6692&snapshot=611):5
    #15 0x7f5722f1eeaf in operator()<(lambda at [third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.cpp:98](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.cpp?l=98&ws=eaeltsin/6692&snapshot=611):15) &> [third_party/llvm/llvm-project/llvm/include/llvm/Support/thread.h:45](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/llvm/include/llvm/Support/thread.h?l=45&ws=eaeltsin/6692&snapshot=611):11
    #16 0x7f5722f1eeaf in __invoke<(lambda at [third_party/llvm/llvm-project/llvm/include/llvm/Support/thread.h:44](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/llvm/include/llvm/Support/thread.h?l=44&ws=eaeltsin/6692&snapshot=611):9), (lambda at [third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.cpp:98](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.cpp?l=98&ws=eaeltsin/6692&snapshot=611):15) &> [third_party/crosstool/v18/llvm_unstable/src/libcxx/include/__type_traits/invoke.h:179](https://cs.corp.google.com/piper///depot/google3/third_party/crosstool/v18/llvm_unstable/src/libcxx/include/__type_traits/invoke.h?l=179&ws=eaeltsin/6692&snapshot=611):25
    #17 0x7f5722f1eeaf in __apply_tuple_impl<(lambda at [third_party/llvm/llvm-project/llvm/include/llvm/Support/thread.h:44](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/llvm/include/llvm/Support/thread.h?l=44&ws=eaeltsin/6692&snapshot=611):9), std::__u::tuple<(lambda at [third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.cpp:98](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.cpp?l=98&ws=eaeltsin/6692&snapshot=611):15)> &, 0UL> third_party/crosstool/v18/llvm_unstable/src/libcxx/include/tuple:1380:5
    #18 0x7f5722f1eeaf in apply<(lambda at [third_party/llvm/llvm-project/llvm/include/llvm/Support/thread.h:44](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/llvm/include/llvm/Support/thread.h?l=44&ws=eaeltsin/6692&snapshot=611):9), std::__u::tuple<(lambda at [third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.cpp:98](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.cpp?l=98&ws=eaeltsin/6692&snapshot=611):15)> &> third_party/crosstool/v18/llvm_unstable/src/libcxx/include/tuple:1384:5
    #19 0x7f5722f1eeaf in GenericThreadProxy<std::__u::tuple<(lambda at [third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.cpp:98](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.cpp?l=98&ws=eaeltsin/6692&snapshot=611):15)> > [third_party/llvm/llvm-project/llvm/include/llvm/Support/thread.h:43](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/llvm/include/llvm/Support/thread.h?l=43&ws=eaeltsin/6692&snapshot=611):5
    #20 0x7f5722f1eeaf in void* llvm::thread::ThreadProxy<std::__u::tuple<clang::clangd::AsyncTaskRunner::runAsync(llvm::Twine const&, llvm::unique_function<void ()>)::$_1>>(void*) [third_party/llvm/llvm-project/llvm/include/llvm/Support/thread.h:57](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/llvm/include/llvm/Support/thread.h?l=57&ws=eaeltsin/6692&snapshot=611):5
    #21 0x55a92182aef0 in asan_thread_start(void*) [third_party/llvm/llvm-project/compiler-rt/lib/asan/asan_interceptors.cpp:239](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/compiler-rt/lib/asan/asan_interceptors.cpp?l=239&ws=eaeltsin/6692&snapshot=611):28
    #22 0x7f5726b477da in start_thread (/usr/grte/v5/lib64/libpthread.so.0+0xb7da) (BuildId: b431ea3122d3e21a60bfe317db5010e3)

previously allocated by thread T48 (task:foo.cpp) here:
    #0 0x55a921867bbd in operator new(unsigned long) [third_party/llvm/llvm-project/compiler-rt/lib/asan/asan_new_delete.cpp:86](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/compiler-rt/lib/asan/asan_new_delete.cpp?l=86&ws=eaeltsin/6692&snapshot=611):3
    #1 0x7f5736d7441e in std::__u::future<std::__u::pair<bool, clang::clangd::SymbolSlab>> std::__u::__make_async_assoc_state<std::__u::pair<bool, clang::clangd::SymbolSlab>, std::__u::__async_func<std::__u::future<std::__u::pair<bool, clang::clangd::SymbolSlab>> clang::clangd::runAsync<std::__u::pair<bool, clang::clangd::SymbolSlab>>(llvm::unique_function<std::__u::pair<bool, clang::clangd::SymbolSlab> ()>)::'lambda'(llvm::unique_function<std::__u::pair<bool, clang::clangd::SymbolSlab> ()>&&, clang::clangd::Context), llvm::unique_function<std::__u::pair<bool, clang::clangd::SymbolSlab> ()>, clang::clangd::Context>>(std::__u::__async_func<std::__u::future<std::__u::pair<bool, clang::clangd::SymbolSlab>> clang::clangd::runAsync<std::__u::pair<bool, clang::clangd::SymbolSlab>>(llvm::unique_function<std::__u::pair<bool, clang::clangd::SymbolSlab> ()>)::'lambda'(llvm::unique_function<std::__u::pair<bool, clang::clangd::SymbolSlab> ()>&&, clang::clangd::Context), llvm::unique_function<std::__u::pair<bool, clang::clangd::SymbolSlab> ()>, clang::clangd::Context>&&) third_party/crosstool/v18/llvm_unstable/src/libcxx/include/future:1833:7
    #2 0x7f5736d7408e in std::__u::future<std::__u::__invoke_result<__decay(std::__u::pair<bool, clang::clangd::SymbolSlab>), __decay(llvm::unique_function<std::__u::pair<bool, clang::clangd::SymbolSlab> ()>), __decay(clang::clangd::Context)>::type> std::__u::async<std::__u::future<std::__u::pair<bool, clang::clangd::SymbolSlab>> clang::clangd::runAsync<std::__u::pair<bool, clang::clangd::SymbolSlab>>(llvm::unique_function<std::__u::pair<bool, clang::clangd::SymbolSlab> ()>)::'lambda'(llvm::unique_function<std::__u::pair<bool, clang::clangd::SymbolSlab> ()>&&, clang::clangd::Context), llvm::unique_function<std::__u::pair<bool, clang::clangd::SymbolSlab> ()>, clang::clangd::Context>(std::__u::launch, std::__u::pair<bool, clang::clangd::SymbolSlab>&&, llvm::unique_function<std::__u::pair<bool, clang::clangd::SymbolSlab> ()>&&, clang::clangd::Context&&) third_party/crosstool/v18/llvm_unstable/src/libcxx/include/future:1878:14
    #3 0x7f5736d52c60 in runAsync<std::__u::pair<bool, clang::clangd::SymbolSlab> > [third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.h:128](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.h?l=128&ws=eaeltsin/6692&snapshot=611):10
    #4 0x7f5736d52c60 in startAsyncFuzzyFind [third_party/llvm/llvm-project/clang-tools-extra/clangd/CodeComplete.cpp:1515](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang-tools-extra/clangd/CodeComplete.cpp?l=1515&ws=eaeltsin/6692&snapshot=611):10
    #5 0x7f5736d52c60 in run [third_party/llvm/llvm-project/clang-tools-extra/clangd/CodeComplete.cpp:1657](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang-tools-extra/clangd/CodeComplete.cpp?l=1657&ws=eaeltsin/6692&snapshot=611):31
    #6 0x7f5736d52c60 in clang::clangd::codeComplete(llvm::StringRef, clang::clangd::Position, clang::clangd::PreambleData const*, clang::clangd::ParseInputs const&, clang::clangd::CodeCompleteOptions, clang::clangd::SpeculativeFuzzyFind*) [third_party/llvm/llvm-project/clang-tools-extra/clangd/CodeComplete.cpp:2304](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang-tools-extra/clangd/CodeComplete.cpp?l=2304&ws=eaeltsin/6692&snapshot=611):32
    #7 0x7f5736d365ca in operator() [third_party/llvm/llvm-project/clang-tools-extra/clangd/ClangdServer.cpp:460](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang-tools-extra/clangd/ClangdServer.cpp?l=460&ws=eaeltsin/6692&snapshot=611):33
    #8 0x7f5736d365ca in void llvm::detail::UniqueFunctionBase<void, llvm::Expected<clang::clangd::InputsAndPreamble>>::CallImpl<clang::clangd::ClangdServer::codeComplete(llvm::StringRef, clang::clangd::Position, clang::clangd::CodeCompleteOptions const&, llvm::unique_function<void (llvm::Expected<clang::clangd::CodeCompleteResult>)>)::$_0>(void*, llvm::Expected<clang::clangd::InputsAndPreamble>&) [third_party/llvm/llvm-project/llvm/include/llvm/ADT/FunctionExtras.h:222](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/llvm/include/llvm/ADT/FunctionExtras.h?l=222&ws=eaeltsin/6692&snapshot=611):12
    #9 0x7f57370b022c in operator() [third_party/llvm/llvm-project/llvm/include/llvm/ADT/FunctionExtras.h:387](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/llvm/include/llvm/ADT/FunctionExtras.h?l=387&ws=eaeltsin/6692&snapshot=611):12
    #10 0x7f57370b022c in operator() [third_party/llvm/llvm-project/clang-tools-extra/clangd/TUScheduler.cpp:1811](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang-tools-extra/clangd/TUScheduler.cpp?l=1811&ws=eaeltsin/6692&snapshot=611):5
    #11 0x7f57370b022c in void llvm::detail::UniqueFunctionBase<void>::CallImpl<clang::clangd::TUScheduler::runWithPreamble(llvm::StringRef, llvm::StringRef, clang::clangd::TUScheduler::PreambleConsistency, llvm::unique_function<void (llvm::Expected<clang::clangd::InputsAndPreamble>)>)::$_0>(void*) [third_party/llvm/llvm-project/llvm/include/llvm/ADT/FunctionExtras.h:222](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/llvm/include/llvm/ADT/FunctionExtras.h?l=222&ws=eaeltsin/6692&snapshot=611):12
    #12 0x7f5722f1eeaf in operator() [third_party/llvm/llvm-project/llvm/include/llvm/ADT/FunctionExtras.h:387](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/llvm/include/llvm/ADT/FunctionExtras.h?l=387&ws=eaeltsin/6692&snapshot=611):12
    #13 0x7f5722f1eeaf in operator() [third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.cpp:101](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.cpp?l=101&ws=eaeltsin/6692&snapshot=611):5
    #14 0x7f5722f1eeaf in operator()<(lambda at [third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.cpp:98](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.cpp?l=98&ws=eaeltsin/6692&snapshot=611):15) &> [third_party/llvm/llvm-project/llvm/include/llvm/Support/thread.h:45](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/llvm/include/llvm/Support/thread.h?l=45&ws=eaeltsin/6692&snapshot=611):11
    #15 0x7f5722f1eeaf in __invoke<(lambda at [third_party/llvm/llvm-project/llvm/include/llvm/Support/thread.h:44](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/llvm/include/llvm/Support/thread.h?l=44&ws=eaeltsin/6692&snapshot=611):9), (lambda at [third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.cpp:98](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.cpp?l=98&ws=eaeltsin/6692&snapshot=611):15) &> [third_party/crosstool/v18/llvm_unstable/src/libcxx/include/__type_traits/invoke.h:179](https://cs.corp.google.com/piper///depot/google3/third_party/crosstool/v18/llvm_unstable/src/libcxx/include/__type_traits/invoke.h?l=179&ws=eaeltsin/6692&snapshot=611):25
    #16 0x7f5722f1eeaf in __apply_tuple_impl<(lambda at [third_party/llvm/llvm-project/llvm/include/llvm/Support/thread.h:44](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/llvm/include/llvm/Support/thread.h?l=44&ws=eaeltsin/6692&snapshot=611):9), std::__u::tuple<(lambda at [third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.cpp:98](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.cpp?l=98&ws=eaeltsin/6692&snapshot=611):15)> &, 0UL> third_party/crosstool/v18/llvm_unstable/src/libcxx/include/tuple:1380:5
    #17 0x7f5722f1eeaf in apply<(lambda at [third_party/llvm/llvm-project/llvm/include/llvm/Support/thread.h:44](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/llvm/include/llvm/Support/thread.h?l=44&ws=eaeltsin/6692&snapshot=611):9), std::__u::tuple<(lambda at [third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.cpp:98](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.cpp?l=98&ws=eaeltsin/6692&snapshot=611):15)> &> third_party/crosstool/v18/llvm_unstable/src/libcxx/include/tuple:1384:5
    #18 0x7f5722f1eeaf in GenericThreadProxy<std::__u::tuple<(lambda at [third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.cpp:98](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.cpp?l=98&ws=eaeltsin/6692&snapshot=611):15)> > [third_party/llvm/llvm-project/llvm/include/llvm/Support/thread.h:43](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/llvm/include/llvm/Support/thread.h?l=43&ws=eaeltsin/6692&snapshot=611):5
    #19 0x7f5722f1eeaf in void* llvm::thread::ThreadProxy<std::__u::tuple<clang::clangd::AsyncTaskRunner::runAsync(llvm::Twine const&, llvm::unique_function<void ()>)::$_1>>(void*) [third_party/llvm/llvm-project/llvm/include/llvm/Support/thread.h:57](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/llvm/include/llvm/Support/thread.h?l=57&ws=eaeltsin/6692&snapshot=611):5
    #20 0x55a92182aef0 in asan_thread_start(void*) [third_party/llvm/llvm-project/compiler-rt/lib/asan/asan_interceptors.cpp:239](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/compiler-rt/lib/asan/asan_interceptors.cpp?l=239&ws=eaeltsin/6692&snapshot=611):28
    #21 0x7f5726b477da in start_thread (/usr/grte/v5/lib64/libpthread.so.0+0xb7da) (BuildId: b431ea3122d3e21a60bfe317db5010e3)

Thread T49 created by T48 (task:foo.cpp) here:
    #0 0x55a921811821 in pthread_create [third_party/llvm/llvm-project/compiler-rt/lib/asan/asan_interceptors.cpp:250](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/compiler-rt/lib/asan/asan_interceptors.cpp?l=250&ws=eaeltsin/6692&snapshot=611):3
    #1 0x7f5736d7451b in __libcpp_thread_create [third_party/crosstool/v18/llvm_unstable/src/libcxx/include/__thread/support/pthread.h:182](https://cs.corp.google.com/piper///depot/google3/third_party/crosstool/v18/llvm_unstable/src/libcxx/include/__thread/support/pthread.h?l=182&ws=eaeltsin/6692&snapshot=611):10
    #2 0x7f5736d7451b in thread<void (std::__u::__async_assoc_state<std::__u::pair<bool, clang::clangd::SymbolSlab>, std::__u::__async_func<(lambda at [third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.h:130](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.h?l=130&ws=eaeltsin/6692&snapshot=611):7), llvm::unique_function<std::__u::pair<bool, clang::clangd::SymbolSlab> ()>, clang::clangd::Context> >::*)(), std::__u::__async_assoc_state<std::__u::pair<bool, clang::clangd::SymbolSlab>, std::__u::__async_func<(lambda at [third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.h:130](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.h?l=130&ws=eaeltsin/6692&snapshot=611):7), llvm::unique_function<std::__u::pair<bool, clang::clangd::SymbolSlab> ()>, clang::clangd::Context> > *, 0> [third_party/crosstool/v18/llvm_unstable/src/libcxx/include/__thread/thread.h:219](https://cs.corp.google.com/piper///depot/google3/third_party/crosstool/v18/llvm_unstable/src/libcxx/include/__thread/thread.h?l=219&ws=eaeltsin/6692&snapshot=611):14
    #3 0x7f5736d7451b in std::__u::future<std::__u::pair<bool, clang::clangd::SymbolSlab>> std::__u::__make_async_assoc_state<std::__u::pair<bool, clang::clangd::SymbolSlab>, std::__u::__async_func<std::__u::future<std::__u::pair<bool, clang::clangd::SymbolSlab>> clang::clangd::runAsync<std::__u::pair<bool, clang::clangd::SymbolSlab>>(llvm::unique_function<std::__u::pair<bool, clang::clangd::SymbolSlab> ()>)::'lambda'(llvm::unique_function<std::__u::pair<bool, clang::clangd::SymbolSlab> ()>&&, clang::clangd::Context), llvm::unique_function<std::__u::pair<bool, clang::clangd::SymbolSlab> ()>, clang::clangd::Context>>(std::__u::__async_func<std::__u::future<std::__u::pair<bool, clang::clangd::SymbolSlab>> clang::clangd::runAsync<std::__u::pair<bool, clang::clangd::SymbolSlab>>(llvm::unique_function<std::__u::pair<bool, clang::clangd::SymbolSlab> ()>)::'lambda'(llvm::unique_function<std::__u::pair<bool, clang::clangd::SymbolSlab> ()>&&, clang::clangd::Context), llvm::unique_function<std::__u::pair<bool, clang::clangd::SymbolSlab> ()>, clang::clangd::Context>&&) third_party/crosstool/v18/llvm_unstable/src/libcxx/include/future:1834:3
    #4 0x7f5736d7408e in std::__u::future<std::__u::__invoke_result<__decay(std::__u::pair<bool, clang::clangd::SymbolSlab>), __decay(llvm::unique_function<std::__u::pair<bool, clang::clangd::SymbolSlab> ()>), __decay(clang::clangd::Context)>::type> std::__u::async<std::__u::future<std::__u::pair<bool, clang::clangd::SymbolSlab>> clang::clangd::runAsync<std::__u::pair<bool, clang::clangd::SymbolSlab>>(llvm::unique_function<std::__u::pair<bool, clang::clangd::SymbolSlab> ()>)::'lambda'(llvm::unique_function<std::__u::pair<bool, clang::clangd::SymbolSlab> ()>&&, clang::clangd::Context), llvm::unique_function<std::__u::pair<bool, clang::clangd::SymbolSlab> ()>, clang::clangd::Context>(std::__u::launch, std::__u::pair<bool, clang::clangd::SymbolSlab>&&, llvm::unique_function<std::__u::pair<bool, clang::clangd::SymbolSlab> ()>&&, clang::clangd::Context&&) third_party/crosstool/v18/llvm_unstable/src/libcxx/include/future:1878:14
    #5 0x7f5736d52c60 in runAsync<std::__u::pair<bool, clang::clangd::SymbolSlab> > [third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.h:128](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.h?l=128&ws=eaeltsin/6692&snapshot=611):10
    #6 0x7f5736d52c60 in startAsyncFuzzyFind [third_party/llvm/llvm-project/clang-tools-extra/clangd/CodeComplete.cpp:1515](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang-tools-extra/clangd/CodeComplete.cpp?l=1515&ws=eaeltsin/6692&snapshot=611):10
    #7 0x7f5736d52c60 in run [third_party/llvm/llvm-project/clang-tools-extra/clangd/CodeComplete.cpp:1657](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang-tools-extra/clangd/CodeComplete.cpp?l=1657&ws=eaeltsin/6692&snapshot=611):31
    #8 0x7f5736d52c60 in clang::clangd::codeComplete(llvm::StringRef, clang::clangd::Position, clang::clangd::PreambleData const*, clang::clangd::ParseInputs const&, clang::clangd::CodeCompleteOptions, clang::clangd::SpeculativeFuzzyFind*) [third_party/llvm/llvm-project/clang-tools-extra/clangd/CodeComplete.cpp:2304](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang-tools-extra/clangd/CodeComplete.cpp?l=2304&ws=eaeltsin/6692&snapshot=611):32
    #9 0x7f5736d365ca in operator() [third_party/llvm/llvm-project/clang-tools-extra/clangd/ClangdServer.cpp:460](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang-tools-extra/clangd/ClangdServer.cpp?l=460&ws=eaeltsin/6692&snapshot=611):33
    #10 0x7f5736d365ca in void llvm::detail::UniqueFunctionBase<void, llvm::Expected<clang::clangd::InputsAndPreamble>>::CallImpl<clang::clangd::ClangdServer::codeComplete(llvm::StringRef, clang::clangd::Position, clang::clangd::CodeCompleteOptions const&, llvm::unique_function<void (llvm::Expected<clang::clangd::CodeCompleteResult>)>)::$_0>(void*, llvm::Expected<clang::clangd::InputsAndPreamble>&) [third_party/llvm/llvm-project/llvm/include/llvm/ADT/FunctionExtras.h:222](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/llvm/include/llvm/ADT/FunctionExtras.h?l=222&ws=eaeltsin/6692&snapshot=611):12
    #11 0x7f57370b022c in operator() [third_party/llvm/llvm-project/llvm/include/llvm/ADT/FunctionExtras.h:387](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/llvm/include/llvm/ADT/FunctionExtras.h?l=387&ws=eaeltsin/6692&snapshot=611):12
    #12 0x7f57370b022c in operator() [third_party/llvm/llvm-project/clang-tools-extra/clangd/TUScheduler.cpp:1811](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang-tools-extra/clangd/TUScheduler.cpp?l=1811&ws=eaeltsin/6692&snapshot=611):5
    #13 0x7f57370b022c in void llvm::detail::UniqueFunctionBase<void>::CallImpl<clang::clangd::TUScheduler::runWithPreamble(llvm::StringRef, llvm::StringRef, clang::clangd::TUScheduler::PreambleConsistency, llvm::unique_function<void (llvm::Expected<clang::clangd::InputsAndPreamble>)>)::$_0>(void*) [third_party/llvm/llvm-project/llvm/include/llvm/ADT/FunctionExtras.h:222](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/llvm/include/llvm/ADT/FunctionExtras.h?l=222&ws=eaeltsin/6692&snapshot=611):12
    #14 0x7f5722f1eeaf in operator() [third_party/llvm/llvm-project/llvm/include/llvm/ADT/FunctionExtras.h:387](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/llvm/include/llvm/ADT/FunctionExtras.h?l=387&ws=eaeltsin/6692&snapshot=611):12
    #15 0x7f5722f1eeaf in operator() [third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.cpp:101](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.cpp?l=101&ws=eaeltsin/6692&snapshot=611):5
    #16 0x7f5722f1eeaf in operator()<(lambda at [third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.cpp:98](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.cpp?l=98&ws=eaeltsin/6692&snapshot=611):15) &> [third_party/llvm/llvm-project/llvm/include/llvm/Support/thread.h:45](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/llvm/include/llvm/Support/thread.h?l=45&ws=eaeltsin/6692&snapshot=611):11
    #17 0x7f5722f1eeaf in __invoke<(lambda at [third_party/llvm/llvm-project/llvm/include/llvm/Support/thread.h:44](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/llvm/include/llvm/Support/thread.h?l=44&ws=eaeltsin/6692&snapshot=611):9), (lambda at [third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.cpp:98](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.cpp?l=98&ws=eaeltsin/6692&snapshot=611):15) &> [third_party/crosstool/v18/llvm_unstable/src/libcxx/include/__type_traits/invoke.h:179](https://cs.corp.google.com/piper///depot/google3/third_party/crosstool/v18/llvm_unstable/src/libcxx/include/__type_traits/invoke.h?l=179&ws=eaeltsin/6692&snapshot=611):25
    #18 0x7f5722f1eeaf in __apply_tuple_impl<(lambda at [third_party/llvm/llvm-project/llvm/include/llvm/Support/thread.h:44](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/llvm/include/llvm/Support/thread.h?l=44&ws=eaeltsin/6692&snapshot=611):9), std::__u::tuple<(lambda at [third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.cpp:98](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.cpp?l=98&ws=eaeltsin/6692&snapshot=611):15)> &, 0UL> third_party/crosstool/v18/llvm_unstable/src/libcxx/include/tuple:1380:5
    #19 0x7f5722f1eeaf in apply<(lambda at [third_party/llvm/llvm-project/llvm/include/llvm/Support/thread.h:44](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/llvm/include/llvm/Support/thread.h?l=44&ws=eaeltsin/6692&snapshot=611):9), std::__u::tuple<(lambda at [third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.cpp:98](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.cpp?l=98&ws=eaeltsin/6692&snapshot=611):15)> &> third_party/crosstool/v18/llvm_unstable/src/libcxx/include/tuple:1384:5
    #20 0x7f5722f1eeaf in GenericThreadProxy<std::__u::tuple<(lambda at [third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.cpp:98](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.cpp?l=98&ws=eaeltsin/6692&snapshot=611):15)> > [third_party/llvm/llvm-project/llvm/include/llvm/Support/thread.h:43](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/llvm/include/llvm/Support/thread.h?l=43&ws=eaeltsin/6692&snapshot=611):5
    #21 0x7f5722f1eeaf in void* llvm::thread::ThreadProxy<std::__u::tuple<clang::clangd::AsyncTaskRunner::runAsync(llvm::Twine const&, llvm::unique_function<void ()>)::$_1>>(void*) [third_party/llvm/llvm-project/llvm/include/llvm/Support/thread.h:57](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/llvm/include/llvm/Support/thread.h?l=57&ws=eaeltsin/6692&snapshot=611):5
    #22 0x55a92182aef0 in asan_thread_start(void*) [third_party/llvm/llvm-project/compiler-rt/lib/asan/asan_interceptors.cpp:239](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/compiler-rt/lib/asan/asan_interceptors.cpp?l=239&ws=eaeltsin/6692&snapshot=611):28
    #23 0x7f5726b477da in start_thread (/usr/grte/v5/lib64/libpthread.so.0+0xb7da) (BuildId: b431ea3122d3e21a60bfe317db5010e3)

Thread T48 (task:foo.cpp) created by T0 here:
    #0 0x55a921811821 in pthread_create [third_party/llvm/llvm-project/compiler-rt/lib/asan/asan_interceptors.cpp:250](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/compiler-rt/lib/asan/asan_interceptors.cpp?l=250&ws=eaeltsin/6692&snapshot=611):3
    #1 0x7f5313cd007a in llvm::llvm_execute_on_thread_impl(void* (*)(void*), void*, std::__u::optional<unsigned int>) third_party/llvm/llvm-project/llvm/lib/Support/Unix/Threading.inc:96:17
    #2 0x7f5722f1e97b in thread<(lambda at [third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.cpp:98](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.cpp?l=98&ws=eaeltsin/6692&snapshot=611):15)> [third_party/llvm/llvm-project/llvm/include/llvm/Support/thread.h:133](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/llvm/include/llvm/Support/thread.h?l=133&ws=eaeltsin/6692&snapshot=611):12
    #3 0x7f5722f1e97b in clang::clangd::AsyncTaskRunner::runAsync(llvm::Twine const&, llvm::unique_function<void ()>) [third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.cpp:107](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang-tools-extra/clangd/support/Threading.cpp?l=107&ws=eaeltsin/6692&snapshot=611):16
    #4 0x7f573709a752 in clang::clangd::TUScheduler::runWithPreamble(llvm::StringRef, llvm::StringRef, clang::clangd::TUScheduler::PreambleConsistency, llvm::unique_function<void (llvm::Expected<clang::clangd::InputsAndPreamble>)>) [third_party/llvm/llvm-project/clang-tools-extra/clangd/TUScheduler.cpp:1814](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang-tools-extra/clangd/TUScheduler.cpp?l=1814&ws=eaeltsin/6692&snapshot=611):18
    #5 0x7f5736d1c29b in clang::clangd::ClangdServer::codeComplete(llvm::StringRef, clang::clangd::Position, clang::clangd::CodeCompleteOptions const&, llvm::unique_function<void (llvm::Expected<clang::clangd::CodeCompleteResult>)>) [third_party/llvm/llvm-project/clang-tools-extra/clangd/ClangdServer.cpp:478](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang-tools-extra/clangd/ClangdServer.cpp?l=478&ws=eaeltsin/6692&snapshot=611):18
    #6 0x7f573a3dd4c5 in clang::clangd::runCodeComplete(clang::clangd::ClangdServer&, llvm::StringRef, clang::clangd::Position, clang::clangd::CodeCompleteOptions) [third_party/llvm/llvm-project/clang-tools-extra/clangd/unittests/SyncAPI.cpp:75](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang-tools-extra/clangd/unittests/SyncAPI.cpp?l=75&ws=eaeltsin/6692&snapshot=611):10
    #7 0x7f573c00ea8e in clang::clangd::(anonymous namespace)::CompletionTest_EnableSpeculativeIndexRequest_Test::TestBody()::$_0::operator()(llvm::StringRef) const [third_party/llvm/llvm-project/clang-tools-extra/clangd/unittests/CodeCompleteTests.cpp:2934](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang-tools-extra/clangd/unittests/CodeCompleteTests.cpp?l=2934&ws=eaeltsin/6692&snapshot=611):25
    #8 0x7f573c00e0f0 in clang::clangd::(anonymous namespace)::CompletionTest_EnableSpeculativeIndexRequest_Test::TestBody() [third_party/llvm/llvm-project/clang-tools-extra/clangd/unittests/CodeCompleteTests.cpp:2949](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/clang-tools-extra/clangd/unittests/CodeCompleteTests.cpp?l=2949&ws=eaeltsin/6692&snapshot=611):3
    #9 0x7f53145ac861 in HandleExceptionsInMethodIfSupported<testing::Test, void> third_party/llvm/llvm-project/third-party/unittest/googletest/src/gtest.cc
    #10 0x7f53145ac861 in testing::Test::Run() [third_party/llvm/llvm-project/third-party/unittest/googletest/src/gtest.cc:2687](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/third-party/unittest/googletest/src/gtest.cc?l=2687&ws=eaeltsin/6692&snapshot=611):5
    #11 0x7f53145ae92c in testing::TestInfo::Run() [third_party/llvm/llvm-project/third-party/unittest/googletest/src/gtest.cc:2836](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/third-party/unittest/googletest/src/gtest.cc?l=2836&ws=eaeltsin/6692&snapshot=611):11
    #12 0x7f53145b01e0 in testing::TestSuite::Run() [third_party/llvm/llvm-project/third-party/unittest/googletest/src/gtest.cc:3015](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/third-party/unittest/googletest/src/gtest.cc?l=3015&ws=eaeltsin/6692&snapshot=611):30
    #13 0x7f53145cc9cf in testing::internal::UnitTestImpl::RunAllTests() [third_party/llvm/llvm-project/third-party/unittest/googletest/src/gtest.cc:5920](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/third-party/unittest/googletest/src/gtest.cc?l=5920&ws=eaeltsin/6692&snapshot=611):44
    #14 0x7f53145cc23d in bool testing::internal::HandleExceptionsInMethodIfSupported<testing::internal::UnitTestImpl, bool>(testing::internal::UnitTestImpl*, bool (testing::internal::UnitTestImpl::*)(), char const*) third_party/llvm/llvm-project/third-party/unittest/googletest/src/gtest.cc
    #15 0x7f53145cc01d in testing::UnitTest::Run() [third_party/llvm/llvm-project/third-party/unittest/googletest/src/gtest.cc:5484](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/third-party/unittest/googletest/src/gtest.cc?l=5484&ws=eaeltsin/6692&snapshot=611):10
    #16 0x7f531522374b in RUN_ALL_TESTS [third_party/llvm/llvm-project/third-party/unittest/googletest/include/gtest/gtest.h:2317](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/third-party/unittest/googletest/include/gtest/gtest.h?l=2317&ws=eaeltsin/6692&snapshot=611):73
    #17 0x7f531522374b in main [third_party/llvm/llvm-project/third-party/unittest/UnitTestMain/TestMain.cpp:75](https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm-project/third-party/unittest/UnitTestMain/TestMain.cpp?l=75&ws=eaeltsin/6692&snapshot=611):10
    #18 0x7f535c9f73d3 in __libc_start_main (/usr/grte/v5/lib64/libc.so.6+0x613d3) (BuildId: 9a996398ce14a94560b0c642eb4f6e94)
    #19 0x55a92178c929 in _start /usr/grte/v5/debug-src/src/csu/../sysdeps/x86_64/start.S:120

kadircet added a commit to kadircet/llvm-project that referenced this pull request Mar 6, 2025
@kadircet
[clangd] Explicitly block until async task completes
5a6a225 
We started seeing some use-after-frees starting with llvm#125433.

This patch ensures we explicitly block for the async task, if there's
one, before destructing std::future, independent of the stdlib
implementation.
kadircet added a commit that referenced this pull request Mar 6, 2025
@kadircet
[clangd] Explicitly block until async task completes (#130077)
8c61ef1 
We started seeing some use-after-frees starting with
#125433.

This patch ensures we explicitly block for the async task, if there's
one, before destructing `std::future`, independent of the stdlib
implementation.
llvm-sync bot pushed a commit to arm/arm-toolchain that referenced this pull request Mar 6, 2025
@kadircet @github-actions
Automerge: [clangd] Explicitly block until async task completes (#130…
be1b666 
…077)

We started seeing some use-after-frees starting with
llvm/llvm-project#125433.

This patch ensures we explicitly block for the async task, if there's
one, before destructing `std::future`, independent of the stdlib
implementation.
@asmok-g
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asmok-g commented Mar 6, 2025

There are other instances to the problem like the one kadircet described in clangd. Sjould we consider reverting the patch ?

@philnik777 philnik777 mentioned this pull request Mar 6, 2025
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@philnik777
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@kadircet @asmok-g I've just uploaded #130145, which I believe addresses your problems. Could you check to make sure I'm not fixing something unrelated?

@kadircet
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hi @philnik777, I guess we're aligned on this being a regression until it's fixed forward and it has been ~2 weeks without it. WDYT about reverting this change and landing it with a fix going forward to minimize the bad commit range ?

@philnik777
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@kadircet Yeah, feel free to revert.

kadircet added a commit that referenced this pull request Mar 10, 2025
@kadircet
Revert "[libc++] Don't try to wait on a thread that hasn't started in…
f059e58 
… std::async (#125433)"

This reverts commit 11766a4.
@shiltian shiltian mentioned this pull request Mar 10, 2025
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@ldionne
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ldionne commented Mar 18, 2025

@kadircet Let's be careful to re-open any closed bugs when a patch is reverted like this :) Otherwise the bug will be forgotten!

@ldionne ldionne mentioned this pull request Mar 18, 2025
Open
jph-13 pushed a commit to jph-13/llvm-project that referenced this pull request Mar 21, 2025
@kadircet @jph-13
[clangd] Explicitly block until async task completes (llvm#130077)
05323da 
We started seeing some use-after-frees starting with
llvm#125433.

This patch ensures we explicitly block for the async task, if there's
one, before destructing `std::future`, independent of the stdlib
implementation.
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@ldionne ldionne ldionne approved these changes

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std::async in future does not throw system_error as required (libc++)
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@philnik777 @llvmbot @slotosch @mysterymath @kadircet @asmok-g @ldionne