Add 'third_party/abseil_cpp/' from commit '768eb2ca28'

git-subtree-dir: third_party/abseil_cpp
git-subtree-mainline: ffb2ae54be
git-subtree-split: 768eb2ca28

third_party/abseil_cpp/absl/debugging/internal/examine_stack.h

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+//
+// Copyright 2018 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.
+//
+
+#ifndef ABSL_DEBUGGING_INTERNAL_EXAMINE_STACK_H_
+#define ABSL_DEBUGGING_INTERNAL_EXAMINE_STACK_H_
+
+#include "absl/base/config.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace debugging_internal {
+
+// Returns the program counter from signal context, or nullptr if
+// unknown. `vuc` is a ucontext_t*. We use void* to avoid the use of
+// ucontext_t on non-POSIX systems.
+void* GetProgramCounter(void* vuc);
+
+// Uses `writerfn` to dump the program counter, stack trace, and stack
+// frame sizes.
+void DumpPCAndFrameSizesAndStackTrace(
+    void* pc, void* const stack[], int frame_sizes[], int depth,
+    int min_dropped_frames, bool symbolize_stacktrace,
+    void (*writerfn)(const char*, void*), void* writerfn_arg);
+
+}  // namespace debugging_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_DEBUGGING_INTERNAL_EXAMINE_STACK_H_