Return 0 from State::iterations() when not yet started. (#598)

* Return a reasonable value from State::iterations() even before starting a benchmark * Optimize State::iterations() for started case.

Return 0 from State::iterations() when not yet started. (#598)
ce3fde16 · Samuel Panzer · Dominic Hamon · 6d74c062 · ce3fde16 · ce3fde16
Commit ce3fde16 authored May 24, 2018 by Samuel Panzer Committed by Dominic Hamon May 24, 2018
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benchmark.h include/benchmark/benchmark.h +4 -1

basic_test.cc test/basic_test.cc +1 -0

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--- a/include/benchmark/benchmark.h
+++ b/include/benchmark/benchmark.h
@@ -575,7 +575,10 @@ class State {

  BENCHMARK_ALWAYS_INLINE
  size_t iterations() const {
-    return (max_iterations - total_iterations_ + batch_leftover_);
+    if (BENCHMARK_BUILTIN_EXPECT(!started_, false)) {
+      return 0;
+    }
+    return max_iterations - total_iterations_ + batch_leftover_;
  }

 private: // items we expect on the first cache line (ie 64 bytes of the struct)

--- a/test/basic_test.cc
+++ b/test/basic_test.cc
@@ -99,6 +99,7 @@ BENCHMARK(BM_empty_stop_start)->ThreadPerCpu();

 void BM_KeepRunning(benchmark::State& state) {
  size_t iter_count = 0;
+  assert(iter_count == state.iterations());
  while (state.KeepRunning()) {
    ++iter_count;
  }