[clangd-dev] [cfe-dev] [clangd] Worker threads stack size

Ilya Biryukov via clangd-dev clangd-dev at lists.llvm.org
Fri Aug 17 06:27:05 PDT 2018

Would be nice to get around this limitation in the standard library. I
don't think we can do it in a standard-compliant way, though.
There's `llvm::llvm_execute_on_thread`, but it is an OS-specific

Are there any ways to set default stack sizes for the newly created
threads? Even if it's platform-specific code, it should be pretty localized
and we could reuse the STL implementation of threads.
I don't know of reliable APIs to do that, unfortunately.

On Fri, Aug 17, 2018 at 2:43 PM Eric Liu <ioeric at google.com> wrote:

> +clangd-dev at lists.llvm.org <clangd-dev at lists.llvm.org> +Ilya Biryukov
> <ibiryukov at google.com>
> On Fri, Aug 17, 2018 at 2:41 PM Dmitry.Kozhevnikov at jetbrains.com via
> cfe-dev <cfe-dev at lists.llvm.org> wrote:
>> Hello!
>> clangd uses std::thread for spawning worker threads to parse files (see
>> AsyncTaskRunner::runAsync in tools/clang/tools/extra/clangd/Threading.cpp).
>> Unfortunately, std::thread lacks the ability to customize the stack size,
>> and the default one might be insufficient for parsing complex source files.
>> For example, on macOS, the default stack size for non-main threads is 512K,
>> so the following code causes a stack overflow (on my machine) with clangd,
>> while being way below the default constexpr evaluation depth threshold:
>>         constexpr int foo(int x) {
>>             return x == 1 ? 1 : foo(x - 1) + 1;
>>         }
>>         static_assert(foo(50) > 0, "");
>> This also can be observed on some real-world projects.
>> Do I understand correctly that the only way to fix it would be to abandon
>> std::thread and reimplement the platform-specific thread spawning (using
>> pthreads/WinAPI), or is there another solution available in LLVM/clang
>> codebase?
>> Best regards,
>> Dmitry Kozhevnikov._______________________________________________
>> cfe-dev mailing list
>> cfe-dev at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev

Ilya Biryukov
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