Thread: set name

spec/std/thread_spec.cr

@@ -49,4 +49,17 @@ describe Thread do
 
     thread.join
   end
+
+  it "names the thread" do
+    Thread.current.name.should be_nil
+    name = nil
+
+    thread = Thread.new(name: "some-name") do
+      name = Thread.current.name
+    end
+    thread.name.should eq("some-name")
+
+    thread.join
+    name.should eq("some-name")
+  end
 end

src/crystal/scheduler.cr

@@ -234,7 +234,7 @@ class Crystal::Scheduler
           Thread.current.scheduler.enqueue worker_loop
           Thread.current
         else
-          Thread.new do
+          Thread.new(name: "CRYSTAL-MT-#{i}") do
             scheduler = Thread.current.scheduler
             pending.sub(1)
             scheduler.run_loop

src/crystal/system/thread.cr

@@ -17,6 +17,8 @@ module Crystal::System::Thread
   # private def system_close
 
   # private def stack_address : Void*
+
+  # private def system_name=(String) : String
 end
 
 {% if flag?(:wasi) %}
@@ -49,12 +51,14 @@ class Thread
   # :nodoc:
   property previous : Thread?
 
+  getter name : String?
+
   def self.unsafe_each(&)
     threads.unsafe_each { |thread| yield thread }
   end
 
   # Creates and starts a new system thread.
-  def initialize(&@func : ->)
+  def initialize(@name : String? = nil, &@func : ->)
     @system_handle = uninitialized Crystal::System::Thread::Handle
     init_handle
   end
@@ -104,6 +108,12 @@ class Thread
     Crystal::System::Thread.yield_current
   end
 
+  # Changes the name of the current thread.
+  def self.name=(name : String) : String
+    thread = Thread.current
+    thread.name = name
+  end
+
   # :nodoc:
   getter scheduler : Crystal::Scheduler { Crystal::Scheduler.new(self) }
 
@@ -112,6 +122,10 @@ class Thread
     Thread.current = self
     @main_fiber = fiber = Fiber.new(stack_address, self)
 
+    if name = @name
+      self.system_name = name
+    end
+
     begin
       @func.call
     rescue ex
@@ -123,6 +137,11 @@ class Thread
     end
   end
 
+  protected def name=(name : String)
+    @name = name
+    self.system_name = @name
+  end
+
   # Holds the GC thread handler
   property gc_thread_handler : Void* = Pointer(Void).null
 end

src/crystal/system/unix/pthread.cr

@@ -112,6 +112,23 @@ module Crystal::System::Thread
 
     address
   end
+
+  # Warning: must be called from the current thread itself, because Darwin
+  # doesn't allow to set the name of any thread but the current one!
+  private def system_name=(name : String) : String
+    {% if flag?(:darwin) %}
+      LibC.pthread_setname_np(name)
+    {% elsif flag?(:netbsd) %}
+      LibC.pthread_setname_np(@system_handle, name, nil)
+    {% elsif LibC.has_method?(:pthread_setname_np) %}
+      LibC.pthread_setname_np(@system_handle, name)
+    {% elsif LibC.has_method?(:pthread_set_name_np) %}
+      LibC.pthread_set_name_np(@system_handle, name)
+    {% else %}
+      {% raise "No `Crystal::System::Thread#system_name` implementation available" %}
+    {% end %}
+    name
+  end
 end
 
 # In musl (alpine) the calls to unwind API segfaults

src/crystal/system/win32/thread.cr

@@ -72,4 +72,11 @@ module Crystal::System::Thread
       low_limit
     {% end %}
   end
+
+  private def system_name=(name : String) : String
+    {% if LibC.has_method?(:SetThreadDescription) %}
+      LibC.SetThreadDescription(@system_handle, System.to_wstr(name))
+    {% end %}
+    name
+  end
 end

src/lib_c/aarch64-android/c/pthread.cr

@@ -38,6 +38,7 @@ lib LibC
   fun pthread_mutex_unlock(__mutex : PthreadMutexT*) : Int
 
   fun pthread_self : PthreadT
+  fun pthread_setname_np(__key : PthreadT, __name : Char*) : Int
 
   fun pthread_setspecific(__key : PthreadKeyT, __value : Void*) : Int
 end

src/lib_c/aarch64-darwin/c/pthread.cr

@@ -25,4 +25,5 @@ lib LibC
   fun pthread_mutex_trylock(x0 : PthreadMutexT*) : Int
   fun pthread_mutex_unlock(x0 : PthreadMutexT*) : Int
   fun pthread_self : PthreadT
+  fun pthread_setname_np(Char*) : Int
 end

src/lib_c/aarch64-linux-gnu/c/pthread.cr

@@ -36,4 +36,5 @@ lib LibC
   fun pthread_mutex_trylock(mutex : PthreadMutexT*) : Int
   fun pthread_mutex_unlock(mutex : PthreadMutexT*) : Int
   fun pthread_self : PthreadT
+  fun pthread_setname_np(PthreadT, Char*) : Int
 end

src/lib_c/aarch64-linux-musl/c/pthread.cr

@@ -27,4 +27,5 @@ lib LibC
   fun pthread_mutex_trylock(x0 : PthreadMutexT*) : Int
   fun pthread_mutex_unlock(x0 : PthreadMutexT*) : Int
   fun pthread_self : PthreadT
+  fun pthread_setname_np(PthreadT, Char*) : Int
 end

src/lib_c/arm-linux-gnueabihf/c/pthread.cr

@@ -36,4 +36,5 @@ lib LibC
   fun pthread_mutex_trylock(mutex : PthreadMutexT*) : Int
   fun pthread_mutex_unlock(mutex : PthreadMutexT*) : Int
   fun pthread_self : PthreadT
+  fun pthread_setname_np(PthreadT, Char*) : Int
 end

src/lib_c/i386-linux-gnu/c/pthread.cr

@@ -35,4 +35,5 @@ lib LibC
   fun pthread_mutex_trylock(mutex : PthreadMutexT*) : Int
   fun pthread_mutex_unlock(mutex : PthreadMutexT*) : Int
   fun pthread_self : PthreadT
+  fun pthread_setname_np(PthreadT, Char*) : Int
 end

src/lib_c/i386-linux-musl/c/pthread.cr

@@ -27,4 +27,5 @@ lib LibC
   fun pthread_mutex_trylock(x0 : PthreadMutexT*) : Int
   fun pthread_mutex_unlock(x0 : PthreadMutexT*) : Int
   fun pthread_self : PthreadT
+  fun pthread_setname_np(PthreadT, Char*) : Int
 end

src/lib_c/x86_64-darwin/c/pthread.cr

@@ -25,4 +25,5 @@ lib LibC
   fun pthread_mutex_trylock(x0 : PthreadMutexT*) : Int
   fun pthread_mutex_unlock(x0 : PthreadMutexT*) : Int
   fun pthread_self : PthreadT
+  fun pthread_setname_np(Char*) : Int
 end

src/lib_c/x86_64-dragonfly/c/pthread.cr

@@ -29,4 +29,5 @@ lib LibC
   fun pthread_mutex_trylock(x0 : PthreadMutexT*) : Int
   fun pthread_mutex_unlock(x0 : PthreadMutexT*) : Int
   fun pthread_self : PthreadT
+  fun pthread_setname_np(PthreadT, Char*) : Int
 end

src/lib_c/x86_64-freebsd/c/pthread.cr

@@ -29,4 +29,5 @@ lib LibC
   fun pthread_mutex_trylock(x0 : PthreadMutexT*) : Int
   fun pthread_mutex_unlock(x0 : PthreadMutexT*) : Int
   fun pthread_self : PthreadT
+  fun pthread_set_name_np(PthreadT, Char*)
 end

src/lib_c/x86_64-linux-gnu/c/pthread.cr

@@ -35,4 +35,5 @@ lib LibC
   fun pthread_mutex_trylock(mutex : PthreadMutexT*) : Int
   fun pthread_mutex_unlock(mutex : PthreadMutexT*) : Int
   fun pthread_self : PthreadT
+  fun pthread_setname_np(PthreadT, Char*) : Int
 end

src/lib_c/x86_64-linux-musl/c/pthread.cr

@@ -27,4 +27,5 @@ lib LibC
   fun pthread_mutex_trylock(x0 : PthreadMutexT*) : Int
   fun pthread_mutex_unlock(x0 : PthreadMutexT*) : Int
   fun pthread_self : PthreadT
+  fun pthread_setname_np(PthreadT, Char*) : Int
 end

src/lib_c/x86_64-netbsd/c/pthread.cr

@@ -35,5 +35,6 @@ lib LibC
   fun pthread_mutex_trylock(x0 : PthreadMutexT*) : Int
   fun pthread_mutex_unlock(x0 : PthreadMutexT*) : Int
   fun pthread_self : PthreadT
+  fun pthread_setname_np(PthreadT, Char*, Void*) : Int
   fun pthread_setspecific(PthreadKeyT, Void*) : Int
 end

src/lib_c/x86_64-openbsd/c/pthread.cr

@@ -30,6 +30,7 @@ lib LibC
   fun pthread_mutex_trylock(x0 : PthreadMutexT*) : Int
   fun pthread_mutex_unlock(x0 : PthreadMutexT*) : Int
   fun pthread_self : PthreadT
+  fun pthread_set_name_np(PthreadT, Char*)
   fun pthread_setspecific(PthreadKeyT, Void*) : Int
   fun pthread_stackseg_np(PthreadT, StackT*) : Int
 end

src/lib_c/x86_64-windows-msvc/c/processthreadsapi.cr

@@ -50,6 +50,9 @@ lib LibC
                      bInheritHandles : BOOL, dwCreationFlags : DWORD,
                      lpEnvironment : Void*, lpCurrentDirectory : LPWSTR,
                      lpStartupInfo : STARTUPINFOW*, lpProcessInformation : PROCESS_INFORMATION*) : BOOL
+  {% if LibC::WIN32_WINNT >= LibC::WIN32_WINNT_WIN10 %}
+    fun SetThreadDescription(hThread : HANDLE, lpThreadDescription : LPWSTR) : LONG
+  {% end %}
   fun SetThreadStackGuarantee(stackSizeInBytes : DWORD*) : BOOL
   fun GetProcessTimes(hProcess : HANDLE, lpCreationTime : FILETIME*, lpExitTime : FILETIME*,
                       lpKernelTime : FILETIME*, lpUserTime : FILETIME*) : BOOL