Use AnyInvocable in internal thread_pool

PiperOrigin-RevId: 488676817
Change-Id: I13f15bb93ab6dda4c56caf969be3c14f84ada6a0

absl/synchronization/BUILD.bazel

@@ -200,6 +200,7 @@ cc_library(
     deps = [
         ":synchronization",
         "//absl/base:core_headers",
+        "//absl/functional:any_invocable",
     ],
 )
 

absl/synchronization/CMakeLists.txt

@@ -136,8 +136,9 @@ absl_cc_library(
   COPTS
     ${ABSL_DEFAULT_COPTS}
   DEPS
-    absl::synchronization
+    absl::any_invocable
     absl::core_headers
+    absl::synchronization
   TESTONLY
 )
 

absl/synchronization/internal/thread_pool.h

@@ -20,9 +20,11 @@
 #include <functional>
 #include <queue>
 #include <thread>  // NOLINT(build/c++11)
+#include <utility>
 #include <vector>
 
 #include "absl/base/thread_annotations.h"
+#include "absl/functional/any_invocable.h"
 #include "absl/synchronization/mutex.h"
 
 namespace absl {
@@ -33,6 +35,7 @@ namespace synchronization_internal {
 class ThreadPool {
  public:
   explicit ThreadPool(int num_threads) {
+    threads_.reserve(num_threads);
     for (int i = 0; i < num_threads; ++i) {
       threads_.push_back(std::thread(&ThreadPool::WorkLoop, this));
     }
@@ -54,7 +57,7 @@ class ThreadPool {
   }
 
   // Schedule a function to be run on a ThreadPool thread immediately.
-  void Schedule(std::function<void()> func) {
+  void Schedule(absl::AnyInvocable<void()> func) {
     assert(func != nullptr);
     absl::MutexLock l(&mu_);
     queue_.push(std::move(func));
@@ -67,7 +70,7 @@ class ThreadPool {
 
   void WorkLoop() {
     while (true) {
-      std::function<void()> func;
+      absl::AnyInvocable<void()> func;
       {
         absl::MutexLock l(&mu_);
         mu_.Await(absl::Condition(this, &ThreadPool::WorkAvailable));
@@ -82,7 +85,7 @@ class ThreadPool {
   }
 
   absl::Mutex mu_;
-  std::queue<std::function<void()>> queue_ ABSL_GUARDED_BY(mu_);
+  std::queue<absl::AnyInvocable<void()>> queue_ ABSL_GUARDED_BY(mu_);
   std::vector<std::thread> threads_;
 };