replace all tag_invoke customizations of start with membr fns

Author: ericniebler

examples/algorithms/retry.hpp

@@ -101,8 +101,8 @@ struct _op {
     }
   }
 
-  friend void tag_invoke(stdexec::start_t, _op& o) noexcept {
-    stdexec::start(*o.o_);
+  void start() & noexcept {
+    stdexec::start(*o_);
   }
 };
 

examples/benchmark/fibonacci.cpp

@@ -49,17 +49,17 @@ struct fib_s {
     long n;
     Scheduler sched;
 
-    friend void tag_invoke(stdexec::start_t, operation& self) noexcept {
-      if (self.n < self.cutoff) {
-        stdexec::set_value(static_cast<Receiver&&>(self.rcvr_), serial_fib(self.n));
+    void start() & noexcept {
+      if (n < cutoff) {
+        stdexec::set_value(static_cast<Receiver&&>(rcvr_), serial_fib(n));
       } else {
         auto mkchild = [&](long n) {
-          return stdexec::starts_on(self.sched, fib_sender(fib_s{self.cutoff, n, self.sched}));
+          return stdexec::starts_on(sched, fib_sender(fib_s{cutoff, n, sched}));
         };
 
         stdexec::start_detached(
-          stdexec::when_all(mkchild(self.n - 1), mkchild(self.n - 2))
-          | stdexec::then([rcvr = static_cast<Receiver&&>(self.rcvr_)](long a, long b) mutable {
+          stdexec::when_all(mkchild(n - 1), mkchild(n - 2))
+          | stdexec::then([rcvr = static_cast<Receiver&&>(rcvr_)](long a, long b) mutable {
               stdexec::set_value(static_cast<Receiver&&>(rcvr), a + b);
             }));
       }

examples/benchmark/static_thread_pool_old.cpp

@@ -17,6 +17,8 @@
 #include "./common.hpp"
 #include "./static_thread_pool_old.hpp"
 
+#include <utility> // IWYU pragma: keep for std::ignore
+
 struct RunThread {
   void operator()(
     exec_old::static_thread_pool& pool,
@@ -29,7 +31,7 @@ struct RunThread {
     std::atomic<bool>& stop,
     exec::numa_policy numa) {
     int numa_node = numa.thread_index_to_node(tid);
-    numa.bind_to_node(numa_node);
+    std::ignore = numa.bind_to_node(numa_node);
     auto scheduler = pool.get_scheduler();
     std::mutex mut;
     std::condition_variable cv;

examples/benchmark/static_thread_pool_old.hpp

@@ -107,7 +107,7 @@ namespace exec_old {
     struct bulk_receiver;
 
     template <class CvrefSenderId, class ReceiverId, std::integral Shape, class Fun>
-    struct bulk_op_state;
+    class bulk_op_state;
 
     struct transform_bulk {
       template <class Data, class Sender>
@@ -430,8 +430,9 @@ namespace exec_old {
       pool_.enqueue(op);
     }
 
-    friend void tag_invoke(stdexec::start_t, operation& op) noexcept {
-      op.enqueue_(&op);
+   public:
+    void start() & noexcept {
+      enqueue_(this);
     }
   };
 
@@ -660,7 +661,7 @@ namespace exec_old {
   };
 
   template <class CvrefSenderId, class ReceiverId, std::integral Shape, class Fun>
-  struct static_thread_pool::bulk_op_state {
+  class static_thread_pool::bulk_op_state {
     using CvrefSender = stdexec::__cvref_t<CvrefSenderId>;
     using Receiver = stdexec::__t<ReceiverId>;
 
@@ -676,13 +677,9 @@ namespace exec_old {
     using inner_op_state = stdexec::connect_result_t<CvrefSender, bulk_rcvr>;
 
     shared_state shared_state_;
-
     inner_op_state inner_op_;
 
-    friend void tag_invoke(stdexec::start_t, bulk_op_state& op) noexcept {
-      stdexec::start(op.inner_op_);
-    }
-
+    public:
     bulk_op_state(
       static_thread_pool& pool,
       Shape shape,
@@ -692,6 +689,10 @@ namespace exec_old {
       : shared_state_(pool, static_cast<Receiver&&>(receiver), shape, fn)
       , inner_op_{stdexec::connect(static_cast<CvrefSender&&>(sender), bulk_rcvr{shared_state_})} {
     }
+
+    void start() & noexcept {
+      stdexec::start(inner_op_);
+    }
   };
 
 } // namespace exec_old

examples/nvexec/maxwell/snr.cuh

@@ -163,15 +163,15 @@ namespace nvexec::_strm::repeat_n {
     std::size_t n_{};
     std::size_t i_{};
 
-    friend void tag_invoke(stdexec::start_t, operation_state_t& op) noexcept {
-      if (op.stream_provider_.status_ != cudaSuccess) {
+    void start() & noexcept {
+      if (this->stream_provider_.status_ != cudaSuccess) {
         // Couldn't allocate memory for operation state, complete with error
-        op.propagate_completion_signal(stdexec::set_error, std::move(op.stream_provider_.status_));
+        this->propagate_completion_signal(stdexec::set_error, std::move(this->stream_provider_.status_));
       } else {
-        if (op.n_) {
-          stdexec::start(*op.pred_op_state_);
+        if (n_) {
+          stdexec::start(*pred_op_state_);
         } else {
-          op.propagate_completion_signal(stdexec::set_value);
+          this->propagate_completion_signal(stdexec::set_value);
         }
       }
     }
@@ -305,11 +305,11 @@ namespace repeat_n_detail {
     std::size_t n_{};
     std::size_t i_{};
 
-    friend void tag_invoke(stdexec::start_t, operation_state_t& op) noexcept {
-      if (op.n_) {
-        stdexec::start(*op.pred_op_state_);
+    void start() & noexcept {
+      if (n_) {
+        stdexec::start(*pred_op_state_);
       } else {
-        stdexec::set_value(std::move(op.rcvr_));
+        stdexec::set_value(std::move(rcvr_));
       }
     }
 

examples/retry.cpp

@@ -31,14 +31,14 @@ struct fail_some {
   struct op {
     R r_;
 
-    friend void tag_invoke(stdexec::start_t, op& self) noexcept {
+    void start() & noexcept {
       static int i = 0;
       if (++i < 3) {
         std::printf("fail!\n");
-        stdexec::set_error(std::move(self.r_), std::exception_ptr{});
+        stdexec::set_error(std::move(r_), std::exception_ptr{});
       } else {
         std::printf("success!\n");
-        stdexec::set_value(std::move(self.r_), 42);
+        stdexec::set_value(std::move(r_), 42);
       }
     }
   };

include/exec/__detail/__system_context_default_impl.hpp

@@ -136,7 +136,7 @@ namespace exec::__system_context_default_impl {
     }
 
     //! Starts the operation that will schedule work on the system scheduler.
-    void start() noexcept {
+    void start() & noexcept {
       stdexec::start(__inner_op_);
     }
 

include/exec/start_now.hpp

@@ -126,7 +126,7 @@ namespace exec {
         , __rcvr_(static_cast<_Receiver&&>(__rcvr)) {
       }
 
-      void start() noexcept {
+      void start() & noexcept {
         const __joiner* expected = &__empty_joiner_;
         if (!__stg_->__joiner_.compare_exchange_strong(expected, this)) {
           join();

test/exec/async_scope/test_spawn.cpp

@@ -19,8 +19,8 @@ namespace {
     struct operation {
       Receiver rcvr_;
 
-      friend void tag_invoke(ex::start_t, operation& self) noexcept {
-        ex::set_value(std::move(self.rcvr_));
+      void start() & noexcept {
+        ex::set_value(std::move(rcvr_));
       }
     };
 

test/exec/async_scope/test_spawn_future.cpp

@@ -32,8 +32,8 @@ namespace {
     struct operation {
       Receiver rcvr_;
 
-      friend void tag_invoke(ex::start_t, operation& self) noexcept {
-        ex::set_value(std::move(self.rcvr_));
+      void start() & noexcept {
+        ex::set_value(std::move(rcvr_));
       }
     };