Give ProfilerManager access to the State being profiled (#2234)

docs/user_guide.md

@@ -1604,6 +1604,11 @@ If set, the `ProfilerManager::AfterSetupStart` and
 end of a separate benchmark run to allow user code to collect and report
 user-provided profile metrics.
 
+From within either hook, `ProfilerManager::GetState()` returns a pointer to
+the `benchmark::State` of the run being profiled, which gives access to run
+information such as the benchmark name (e.g. for registering named profiling
+regions). Outside of the two hooks it returns `nullptr`.
+
 Output collected from this profiling run must be reported separately.
 
 <a name="using-register-benchmark" />

include/benchmark/managers.h

@@ -24,6 +24,8 @@
 
 namespace benchmark {
 
+class State;
+
 class MemoryManager {
  public:
   static constexpr int64_t TombstoneValue = std::numeric_limits<int64_t>::max();
@@ -56,6 +58,17 @@ class ProfilerManager {
   virtual ~ProfilerManager() {}
   virtual void AfterSetupStart() = 0;
   virtual void BeforeTeardownStop() = 0;
+
+ protected:
+  // The State of the benchmark run being profiled, giving access to e.g. the
+  // benchmark name (for a named profiling region). Non-null only while
+  // AfterSetupStart() or BeforeTeardownStop() is executing; any other caller
+  // observes nullptr.
+  const State* GetState() const { return state_; }
+
+ private:
+  friend class State;
+  const State* state_ = nullptr;
 };
 
 BENCHMARK_EXPORT

src/benchmark.cc

@@ -331,7 +331,9 @@ void State::StartKeepRunning() {
   started_ = true;
   total_iterations_ = skipped() ? 0 : max_iterations;
   if (BENCHMARK_BUILTIN_EXPECT(profiler_manager_ != nullptr, false)) {
+    profiler_manager_->state_ = this;
     profiler_manager_->AfterSetupStart();
+    profiler_manager_->state_ = nullptr;
   }
   manager_->StartStopBarrier();
   if (!skipped()) {
@@ -349,7 +351,9 @@ void State::FinishKeepRunning() {
   finished_ = true;
   manager_->StartStopBarrier();
   if (BENCHMARK_BUILTIN_EXPECT(profiler_manager_ != nullptr, false)) {
+    profiler_manager_->state_ = this;
     profiler_manager_->BeforeTeardownStop();
+    profiler_manager_->state_ = nullptr;
   }
 }
 

test/profiler_manager_test.cc

@@ -2,6 +2,7 @@
 
 #include <cassert>
 #include <memory>
+#include <string>
 
 #include "benchmark/benchmark_api.h"
 #include "benchmark/managers.h"
@@ -13,11 +14,21 @@
 namespace {
 class TestProfilerManager : public benchmark::ProfilerManager {
  public:
-  void AfterSetupStart() override { ++start_called; }
+  void AfterSetupStart() override {
+    ++start_called;
+    if (GetState() != nullptr) {
+      benchmark_name = GetState()->name();
+    }
+  }
   void BeforeTeardownStop() override { ++stop_called; }
 
+  // Expose the protected accessor so the harness can verify it yields
+  // nullptr outside the hooks.
+  const benchmark::State* StateOutsideHooks() const { return GetState(); }
+
   int start_called = 0;
   int stop_called = 0;
+  std::string benchmark_name;
 };
 
 void BM_empty(benchmark::State& state) {
@@ -55,4 +66,7 @@ int main(int argc, char* argv[]) {
 
   assert(pm->start_called == 1);
   assert(pm->stop_called == 1);
+  assert(pm->benchmark_name == "BM_empty");
+  // Outside the hooks the state must not be observable.
+  assert(pm->StateOutsideHooks() == nullptr);
 }