Change absl::Status implementation to be amenable to [[clang:trivial_abi]] annotation.

This moves the implementation of most methods from absl::Status to absl::status_internal::StatusRep, and ensures that no calls to absl::Status methods are in a cc file.

Stub implementations checking only inlined rep properties and calling no-op (RepToPointer) or out of line methods exist in status.h

PiperOrigin-RevId: 566187430
Change-Id: I356ec29c0970ffe82eac2a5d98850e647fcd5ea5

2 files changed, 294 insertions, 10 deletions

diff --git a/absl/status/internal/status_internal.cc b/absl/status/internal/status_internal.cc
new file mode 100644
index 00000000..2307579b
--- /dev/null
+++ b/absl/status/internal/status_internal.cc
@@ -0,0 +1,246 @@
+// Copyright 2023 The Abseil Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/status/internal/status_internal.h"
+
+#include <atomic>
+#include <cassert>
+#include <cstddef>
+#include <cstdint>
+#include <cstdio>
+#include <cstring>
+#include <memory>
+#include <string>
+#include <utility>
+
+#include "absl/base/attributes.h"
+#include "absl/base/config.h"
+#include "absl/base/macros.h"
+#include "absl/debugging/stacktrace.h"
+#include "absl/debugging/symbolize.h"
+#include "absl/memory/memory.h"
+#include "absl/status/status.h"
+#include "absl/status/status_payload_printer.h"
+#include "absl/strings/cord.h"
+#include "absl/strings/escaping.h"
+#include "absl/strings/str_cat.h"
+#include "absl/strings/str_format.h"
+#include "absl/strings/str_split.h"
+#include "absl/strings/string_view.h"
+#include "absl/types/optional.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace status_internal {
+
+void StatusRep::Unref() const {
+  // Fast path: if ref==1, there is no need for a RefCountDec (since
+  // this is the only reference and therefore no other thread is
+  // allowed to be mucking with r).
+  if (ref_.load(std::memory_order_acquire) == 1 ||
+      ref_.fetch_sub(1, std::memory_order_acq_rel) - 1 == 0) {
+    delete this;
+  }
+}
+
+static absl::optional<size_t> FindPayloadIndexByUrl(
+    const Payloads* payloads, absl::string_view type_url) {
+  if (payloads == nullptr) return absl::nullopt;
+
+  for (size_t i = 0; i < payloads->size(); ++i) {
+    if ((*payloads)[i].type_url == type_url) return i;
+  }
+
+  return absl::nullopt;
+}
+
+absl::optional<absl::Cord> StatusRep::GetPayload(
+    absl::string_view type_url) const {
+  absl::optional<size_t> index =
+      status_internal::FindPayloadIndexByUrl(payloads_.get(), type_url);
+  if (index.has_value()) return (*payloads_)[index.value()].payload;
+
+  return absl::nullopt;
+}
+
+void StatusRep::SetPayload(absl::string_view type_url, absl::Cord payload) {
+  if (payloads_ == nullptr) {
+    payloads_ = absl::make_unique<status_internal::Payloads>();
+  }
+
+  absl::optional<size_t> index =
+      status_internal::FindPayloadIndexByUrl(payloads_.get(), type_url);
+  if (index.has_value()) {
+    (*payloads_)[index.value()].payload = std::move(payload);
+    return;
+  }
+
+  payloads_->push_back({std::string(type_url), std::move(payload)});
+}
+
+StatusRep::EraseResult StatusRep::ErasePayload(absl::string_view type_url) {
+  absl::optional<size_t> index =
+      status_internal::FindPayloadIndexByUrl(payloads_.get(), type_url);
+  if (!index.has_value()) return {false, Status::PointerToRep(this)};
+  payloads_->erase(payloads_->begin() + index.value());
+  if (payloads_->empty() && message_.empty()) {
+    // Special case: If this can be represented inlined, it MUST be inlined
+    // (== depends on this behavior).
+    EraseResult result = {true, Status::CodeToInlinedRep(code_)};
+    Unref();
+    return result;
+  }
+  return {true, Status::PointerToRep(this)};
+}
+
+void StatusRep::ForEachPayload(
+    absl::FunctionRef<void(absl::string_view, const absl::Cord&)> visitor)
+    const {
+  if (auto* payloads = payloads_.get()) {
+    bool in_reverse =
+        payloads->size() > 1 && reinterpret_cast<uintptr_t>(payloads) % 13 > 6;
+
+    for (size_t index = 0; index < payloads->size(); ++index) {
+      const auto& elem =
+          (*payloads)[in_reverse ? payloads->size() - 1 - index : index];
+
+#ifdef NDEBUG
+      visitor(elem.type_url, elem.payload);
+#else
+      // In debug mode invalidate the type url to prevent users from relying on
+      // this string lifetime.
+
+      // NOLINTNEXTLINE intentional extra conversion to force temporary.
+      visitor(std::string(elem.type_url), elem.payload);
+#endif  // NDEBUG
+    }
+  }
+}
+
+std::string StatusRep::ToString(StatusToStringMode mode) const {
+  std::string text;
+  absl::StrAppend(&text, absl::StatusCodeToString(code()), ": ", message());
+
+  const bool with_payload = (mode & StatusToStringMode::kWithPayload) ==
+                            StatusToStringMode::kWithPayload;
+
+  if (with_payload) {
+    status_internal::StatusPayloadPrinter printer =
+        status_internal::GetStatusPayloadPrinter();
+    this->ForEachPayload([&](absl::string_view type_url,
+                             const absl::Cord& payload) {
+      absl::optional<std::string> result;
+      if (printer) result = printer(type_url, payload);
+      absl::StrAppend(
+          &text, " [", type_url, "='",
+          result.has_value() ? *result : absl::CHexEscape(std::string(payload)),
+          "']");
+    });
+  }
+
+  return text;
+}
+
+bool StatusRep::operator==(const StatusRep& other) const {
+  assert(this != &other);
+  if (code_ != other.code_) return false;
+  if (message_ != other.message_) return false;
+  const status_internal::Payloads* this_payloads = payloads_.get();
+  const status_internal::Payloads* other_payloads = other.payloads_.get();
+
+  const status_internal::Payloads no_payloads;
+  const status_internal::Payloads* larger_payloads =
+      this_payloads ? this_payloads : &no_payloads;
+  const status_internal::Payloads* smaller_payloads =
+      other_payloads ? other_payloads : &no_payloads;
+  if (larger_payloads->size() < smaller_payloads->size()) {
+    std::swap(larger_payloads, smaller_payloads);
+  }
+  if ((larger_payloads->size() - smaller_payloads->size()) > 1) return false;
+  // Payloads can be ordered differently, so we can't just compare payload
+  // vectors.
+  for (const auto& payload : *larger_payloads) {
+
+    bool found = false;
+    for (const auto& other_payload : *smaller_payloads) {
+      if (payload.type_url == other_payload.type_url) {
+        if (payload.payload != other_payload.payload) {
+          return false;
+        }
+        found = true;
+        break;
+      }
+    }
+    if (!found) return false;
+  }
+  return true;
+}
+
+StatusRep* StatusRep::CloneAndUnref() const {
+  // Optimization: no need to create a clone if we already have a refcount of 1.
+  if (ref_.load(std::memory_order_acquire) == 1) {
+    // All StatusRep instances are heap allocated and mutable, therefore this
+    // const_cast will never cast away const from a stack instance.
+    //
+    // CloneAndUnref is the only method that doesn't involve an external cast to
+    // get a mutable StatusRep* from the uintptr_t rep stored in Status.
+    return const_cast<StatusRep*>(this);
+  }
+  std::unique_ptr<status_internal::Payloads> payloads;
+  if (payloads_) {
+    payloads = absl::make_unique<status_internal::Payloads>(*payloads_);
+  }
+  auto* new_rep = new StatusRep(code_, message_, std::move(payloads));
+  Unref();
+  return new_rep;
+}
+
+// Convert canonical code to a value known to this binary.
+absl::StatusCode MapToLocalCode(int value) {
+  absl::StatusCode code = static_cast<absl::StatusCode>(value);
+  switch (code) {
+    case absl::StatusCode::kOk:
+    case absl::StatusCode::kCancelled:
+    case absl::StatusCode::kUnknown:
+    case absl::StatusCode::kInvalidArgument:
+    case absl::StatusCode::kDeadlineExceeded:
+    case absl::StatusCode::kNotFound:
+    case absl::StatusCode::kAlreadyExists:
+    case absl::StatusCode::kPermissionDenied:
+    case absl::StatusCode::kResourceExhausted:
+    case absl::StatusCode::kFailedPrecondition:
+    case absl::StatusCode::kAborted:
+    case absl::StatusCode::kOutOfRange:
+    case absl::StatusCode::kUnimplemented:
+    case absl::StatusCode::kInternal:
+    case absl::StatusCode::kUnavailable:
+    case absl::StatusCode::kDataLoss:
+    case absl::StatusCode::kUnauthenticated:
+      return code;
+    default:
+      return absl::StatusCode::kUnknown;
+  }
+}
+
+std::string* MakeCheckFailString(const absl::Status* status,
+                                 const char* prefix) {
+  return new std::string(
+      absl::StrCat(prefix, " (",
+                   status->ToString(StatusToStringMode::kWithEverything), ")"));
+}
+
+}  // namespace status_internal
+
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/absl/status/internal/status_internal.h b/absl/status/internal/status_internal.h
index f22c611d..a445ce37 100644
--- a/absl/status/internal/status_internal.h
+++ b/absl/status/internal/status_internal.h
@@ -14,13 +14,18 @@
 #ifndef ABSL_STATUS_INTERNAL_STATUS_INTERNAL_H_
 #define ABSL_STATUS_INTERNAL_STATUS_INTERNAL_H_
 
+#include <atomic>
+#include <cstdint>
 #include <memory>
 #include <string>
 #include <utility>
 
 #include "absl/base/attributes.h"
+#include "absl/base/config.h"
 #include "absl/container/inlined_vector.h"
 #include "absl/strings/cord.h"
+#include "absl/strings/string_view.h"
+#include "absl/types/optional.h"
 
 #ifndef SWIG
 // Disabled for SWIG as it doesn't parse attributes correctly.
@@ -44,6 +49,7 @@ namespace absl {
 ABSL_NAMESPACE_BEGIN
 
 enum class StatusCode : int;
+enum class StatusToStringMode : int;
 
 namespace status_internal {
 
@@ -56,22 +62,54 @@ struct Payload {
 using Payloads = absl::InlinedVector<Payload, 1>;
 
 // Reference-counted representation of Status data.
-struct StatusRep {
+class StatusRep {
+ public:
   StatusRep(absl::StatusCode code_arg, absl::string_view message_arg,
             std::unique_ptr<status_internal::Payloads> payloads_arg)
-      : ref(int32_t{1}),
-        code(code_arg),
-        message(message_arg),
-        payloads(std::move(payloads_arg)) {}
-
-  std::atomic<int32_t> ref;
-  absl::StatusCode code;
+      : ref_(int32_t{1}),
+        code_(code_arg),
+        message_(message_arg),
+        payloads_(std::move(payloads_arg)) {}
+
+  absl::StatusCode code() const { return code_; }
+  const std::string& message() const { return message_; }
+
+  // Ref and unref are const to allow access through a const pointer, and are
+  // used during copying operations.
+  void Ref() const { ref_.fetch_add(1, std::memory_order_relaxed); }
+  void Unref() const;
+
+  // Payload methods correspond to the same methods in absl::Status.
+  absl::optional<absl::Cord> GetPayload(absl::string_view type_url) const;
+  void SetPayload(absl::string_view type_url, absl::Cord payload);
+  struct EraseResult {
+    bool erased;
+    uintptr_t new_rep;
+  };
+  EraseResult ErasePayload(absl::string_view type_url);
+  void ForEachPayload(
+      absl::FunctionRef<void(absl::string_view, const absl::Cord&)> visitor)
+      const;
+
+  std::string ToString(StatusToStringMode mode) const;
+
+  bool operator==(const StatusRep& other) const;
+  bool operator!=(const StatusRep& other) const { return !(*this == other); }
+
+  // Returns an equivalent heap allocated StatusRep with refcount 1.
+  //
+  // `this` is not safe to be used after calling as it may have been deleted.
+  StatusRep* CloneAndUnref() const;
+
+ private:
+  mutable std::atomic<int32_t> ref_;
+  absl::StatusCode code_;
 
   // As an internal implementation detail, we guarantee that if status.message()
   // is non-empty, then the resulting string_view is null terminated.
   // This is required to implement 'StatusMessageAsCStr(...)'
-  std::string message;
-  std::unique_ptr<status_internal::Payloads> payloads;
+  std::string message_;
+  std::unique_ptr<status_internal::Payloads> payloads_;
 };
 
 absl::StatusCode MapToLocalCode(int value);