Export of internal Abseil changes

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7f5caec21a1a88db6486b8bc2e5f6d5baba076ed by Derek Mauro <dmauro@google.com>:

Tag absl::StatusOr with [[nodiscard]] when it is available

[[nodiscard]] provides better diagnostics on classes than the current
ABSL_MUST_USE_RESULT, which expands to
__attribute__((warn_unused_result))

Ideally we would make ABSL_MUST_USE_RESULT expand to [[nodiscard]], but
we would need to fix all code to build with [[nodiscard]] first.

PiperOrigin-RevId: 422628161

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236be69f0f34ccaa3adc831075613847797e6557 by Jorg Brown <jorg@google.com>:

Make sure all of absl/strings compiles even with -Wsign-compare and -Wconversion warnings.

PiperOrigin-RevId: 422573904

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005669883a8794e6d19dc4bbb4f0e18032e2fbc9 by Chris Kennelly <ckennelly@google.com>:

Include sampling stride in hashtable sampling data.

This allows us to weight each sample to control for our sampling rate.

PiperOrigin-RevId: 421886935

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78046ce6b429b9f5b6c97b05e8448a791db93bbe by Abseil Team <absl-team@google.com>:

Use __builtin_bit_cast for absl::bit_cast when possible

This makes absl::bit_cast match the requirements of the standard when compiler support exists.

PiperOrigin-RevId: 421883999

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f397461f4bbeabd32437df0f2275663aeb51adb2 by Derek Mauro <dmauro@google.com>:

Tag absl::Status with [[nodiscard]] when it is available

[[nodiscard]] provides better diagnostics on classes than the current
ABSL_MUST_USE_RESULT, which expands to
__attribute__((warn_unused_result))

Ideally we would make ABSL_MUST_USE_RESULT expand to [[nodiscard]], but
we would need to fix all code to build with [[nodiscard]] first.

PiperOrigin-RevId: 421825565
GitOrigin-RevId: 7f5caec21a1a88db6486b8bc2e5f6d5baba076ed
Change-Id: I760b45b68f6012809c70c2a584e4144a99f98733

1 files changed, 13 insertions, 5 deletions

diff --git a/absl/container/internal/hashtablez_sampler.h b/absl/container/internal/hashtablez_sampler.h
index 6738786c..e7c204ee 100644
--- a/absl/container/internal/hashtablez_sampler.h
+++ b/absl/container/internal/hashtablez_sampler.h
@@ -67,7 +67,7 @@ struct HashtablezInfo : public profiling_internal::Sample<HashtablezInfo> {
 
   // Puts the object into a clean state, fills in the logically `const` members,
   // blocking for any readers that are currently sampling the object.
-  void PrepareForSampling(size_t inline_element_size_value)
+  void PrepareForSampling(int64_t stride, size_t inline_element_size_value)
       ABSL_EXCLUSIVE_LOCKS_REQUIRED(init_mu);
 
   // These fields are mutated by the various Record* APIs and need to be
@@ -145,7 +145,15 @@ inline void RecordEraseSlow(HashtablezInfo* info) {
       std::memory_order_relaxed);
 }
 
-HashtablezInfo* SampleSlow(int64_t* next_sample, size_t inline_element_size);
+struct SamplingState {
+  int64_t next_sample;
+  // When we make a sampling decision, we record that distance so we can weight
+  // each sample.
+  int64_t sample_stride;
+};
+
+HashtablezInfo* SampleSlow(SamplingState& next_sample,
+                           size_t inline_element_size);
 void UnsampleSlow(HashtablezInfo* info);
 
 #if defined(ABSL_INTERNAL_HASHTABLEZ_SAMPLE)
@@ -235,7 +243,7 @@ class HashtablezInfoHandle {
 #endif  // defined(ABSL_INTERNAL_HASHTABLEZ_SAMPLE)
 
 #if defined(ABSL_INTERNAL_HASHTABLEZ_SAMPLE)
-extern ABSL_PER_THREAD_TLS_KEYWORD int64_t global_next_sample;
+extern ABSL_PER_THREAD_TLS_KEYWORD SamplingState global_next_sample;
 #endif  // defined(ABSL_INTERNAL_HASHTABLEZ_SAMPLE)
 
 // Returns an RAII sampling handle that manages registration and unregistation
@@ -243,11 +251,11 @@ extern ABSL_PER_THREAD_TLS_KEYWORD int64_t global_next_sample;
 inline HashtablezInfoHandle Sample(
     size_t inline_element_size ABSL_ATTRIBUTE_UNUSED) {
 #if defined(ABSL_INTERNAL_HASHTABLEZ_SAMPLE)
-  if (ABSL_PREDICT_TRUE(--global_next_sample > 0)) {
+  if (ABSL_PREDICT_TRUE(--global_next_sample.next_sample > 0)) {
     return HashtablezInfoHandle(nullptr);
   }
   return HashtablezInfoHandle(
-      SampleSlow(&global_next_sample, inline_element_size));
+      SampleSlow(global_next_sample, inline_element_size));
 #else
   return HashtablezInfoHandle(nullptr);
 #endif  // !ABSL_PER_THREAD_TLS