Export of internal Abseil changes

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caf65de1a20b1ad286796a9eaee38f8b59e93f3b by Samuel Benzaquen <sbenza@google.com>:

Add a benchmark for StrAppend.

PiperOrigin-RevId: 327111569

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2faa53fb3f4090f9609c7dea8951a82e1d72ce3a by Derek Mauro <dmauro@google.com>:

Add the inline namespace to the code generated by
gaussian_distribution_gentables

A previous changed manually added it to the output

PiperOrigin-RevId: 327022780

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29edfd86e49e4d7665e843463f8df3c72467e909 by Derek Mauro <dmauro@google.com>:

Re-write the logic for detecting which stacktrace implementation to use on Linux.

The visible change is to detect the presence of the `<execinfo.h>`
header, which allows using the `backtrace`-based implementation when
it is available.

The logic has been simplified as well.

Fixes #746

PiperOrigin-RevId: 326911875

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ce198204b77aac240e98fc8d5931b17a8b26bac3 by Abseil Team <absl-team@google.com>:

Demangle exception spec.

PiperOrigin-RevId: 326909460

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c41b89954545bdc4430d10e785d3ba64a55122d5 by Abseil Team <absl-team@google.com>:

Add support for inheriting ctor.

PiperOrigin-RevId: 326904919
GitOrigin-RevId: caf65de1a20b1ad286796a9eaee38f8b59e93f3b
Change-Id: Ifd28b6a85a032839cbeafd1b16f88046dfd6c1d4

1 files changed, 47 insertions, 0 deletions

diff --git a/absl/strings/str_cat_benchmark.cc b/absl/strings/str_cat_benchmark.cc
index ee4ad112..02c4dbe6 100644
--- a/absl/strings/str_cat_benchmark.cc
+++ b/absl/strings/str_cat_benchmark.cc
@@ -137,4 +137,51 @@ void BM_DoubleToString_By_SixDigits(benchmark::State& state) {
 }
 BENCHMARK(BM_DoubleToString_By_SixDigits);
 
+template <typename... Chunks>
+void BM_StrAppendImpl(benchmark::State& state, size_t total_bytes,
+                      Chunks... chunks) {
+  for (auto s : state) {
+    std::string result;
+    while (result.size() < total_bytes) {
+      absl::StrAppend(&result, chunks...);
+      benchmark::DoNotOptimize(result);
+    }
+  }
+}
+
+void BM_StrAppend(benchmark::State& state) {
+  const int total_bytes = state.range(0);
+  const int chunks_at_a_time = state.range(1);
+  const absl::string_view kChunk = "0123456789";
+
+  switch (chunks_at_a_time) {
+    case 1:
+      return BM_StrAppendImpl(state, total_bytes, kChunk);
+    case 2:
+      return BM_StrAppendImpl(state, total_bytes, kChunk, kChunk);
+    case 4:
+      return BM_StrAppendImpl(state, total_bytes, kChunk, kChunk, kChunk,
+                              kChunk);
+    case 8:
+      return BM_StrAppendImpl(state, total_bytes, kChunk, kChunk, kChunk,
+                              kChunk, kChunk, kChunk, kChunk, kChunk);
+    default:
+      std::abort();
+  }
+}
+
+template <typename B>
+void StrAppendConfig(B* benchmark) {
+  for (int bytes : {10, 100, 1000, 10000}) {
+    for (int chunks : {1, 2, 4, 8}) {
+      // Only add the ones that divide properly. Otherwise we are over counting.
+      if (bytes % (10 * chunks) == 0) {
+        benchmark->Args({bytes, chunks});
+      }
+    }
+  }
+}
+
+BENCHMARK(BM_StrAppend)->Apply(StrAppendConfig);
+
 }  // namespace