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487 lines
17 KiB
C++
487 lines
17 KiB
C++
#pragma once
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#if defined(__ELF__) && !defined(OS_FREEBSD)
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/*
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* Copyright 2012-present Facebook, Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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/** This file was edited for ClickHouse.
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* Original is from folly library.
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*/
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#include <functional>
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#include <memory>
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#include <optional>
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#include <string>
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#include <string_view>
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#include <variant>
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#include <vector>
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namespace DB
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{
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class Elf;
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/**
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* DWARF record parser.
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*
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* We only implement enough DWARF functionality to convert from PC address
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* to file and line number information.
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*
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* This means (although they're not part of the public API of this class), we
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* can parse Debug Information Entries (DIEs), abbreviations, attributes (of
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* all forms), and we can interpret bytecode for the line number VM.
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*
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* We can interpret DWARF records of version 2, 3, 4, or 5, although we don't
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* actually support many of the features of versions 4 and 5 (such as VLIW, multiple
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* operations per instruction)
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*
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* Note that the DWARF record parser does not allocate heap memory at all.
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* This is on purpose: you can use the parser from
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* memory-constrained situations (such as an exception handler for
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* std::out_of_memory) If it weren't for this requirement, some things would
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* be much simpler: the Path class would be unnecessary and would be replaced
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* with a std::string; the list of file names in the line number VM would be
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* kept as a vector of strings instead of re-executing the program to look for
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* DW_LNE_define_file instructions, etc.
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*/
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class Dwarf final
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{
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// Note that Dwarf uses (and returns) std::string_view a lot.
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// The std::string_view point within sections in the ELF file, and so will
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// be live for as long as the passed-in Elf is live.
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public:
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/** Create a DWARF parser around an ELF file. */
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explicit Dwarf(const std::shared_ptr<Elf> & elf);
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/**
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* More than one location info may exist if current frame is an inline
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* function call.
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*/
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static constexpr uint32_t kMaxInlineLocationInfoPerFrame = 10;
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/**
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* Represent a file path a s collection of three parts (base directory,
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* subdirectory, and file).
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*/
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class Path
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{
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public:
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Path() = default;
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Path(std::string_view baseDir, std::string_view subDir, std::string_view file);
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std::string_view baseDir() const { return baseDir_; }
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std::string_view subDir() const { return subDir_; }
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std::string_view file() const { return file_; }
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size_t size() const;
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/**
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* Copy the Path to a buffer of size bufSize.
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*
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* toBuffer behaves like snprintf: It will always null-terminate the
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* buffer (so it will copy at most bufSize-1 bytes), and it will return
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* the number of bytes that would have been written if there had been
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* enough room, so, if toBuffer returns a value >= bufSize, the output
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* was truncated.
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*/
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size_t toBuffer(char * buf, size_t bufSize) const;
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void toString(std::string & dest) const;
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std::string toString() const
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{
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std::string s;
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toString(s);
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return s;
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}
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// TODO(tudorb): Implement operator==, operator!=; not as easy as it
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// seems as the same path can be represented in multiple ways
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private:
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std::string_view baseDir_; /// NOLINT
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std::string_view subDir_; /// NOLINT
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std::string_view file_; /// NOLINT
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};
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// Indicates inline function `name` is called at `line@file`.
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struct CallLocation
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{
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Path file = {};
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uint64_t line = 0;
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std::string_view name;
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};
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enum class LocationInfoMode : uint8_t
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{
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// Don't resolve location info.
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DISABLED,
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// Perform CU lookup using .debug_aranges (might be incomplete).
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FAST,
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// Scan all CU in .debug_info (slow!) on .debug_aranges lookup failure.
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FULL,
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// Scan .debug_info (super slower, use with caution) for inline functions in
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// addition to FULL.
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FULL_WITH_INLINE,
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};
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struct LocationInfo
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{
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bool has_main_file = false;
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Path main_file;
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bool has_file_and_line = false;
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Path file;
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uint64_t line = 0;
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};
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/**
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* Frame information: symbol name and location.
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*/
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struct SymbolizedFrame
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{
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bool found = false;
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uintptr_t addr = 0;
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// Mangled symbol name. Use `folly::demangle()` to demangle it.
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const char * name = nullptr;
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LocationInfo location;
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std::shared_ptr<const Elf> file;
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void clear() { *this = SymbolizedFrame(); }
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};
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/** Find the file and line number information corresponding to address.
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* The address must be physical - offset in object file without offset in virtual memory where the object is loaded.
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*/
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bool findAddress(uintptr_t address, LocationInfo & info, LocationInfoMode mode, std::vector<SymbolizedFrame> & inline_frames) const;
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private:
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static bool findDebugInfoOffset(uintptr_t address, std::string_view aranges, uint64_t & offset);
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std::shared_ptr<const Elf> elf_; /// NOLINT
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// DWARF section made up of chunks, each prefixed with a length header.
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// The length indicates whether the chunk is DWARF-32 or DWARF-64, which
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// guides interpretation of "section offset" records.
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// (yes, DWARF-32 and DWARF-64 sections may coexist in the same file)
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class Section
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{
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public:
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Section() : is64_bit(false) {}
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explicit Section(std::string_view d);
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// Return next chunk, if any; the 4- or 12-byte length was already
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// parsed and isn't part of the chunk.
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bool next(std::string_view & chunk);
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// Is the current chunk 64 bit?
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bool is64Bit() const { return is64_bit; }
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private:
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// Yes, 32- and 64- bit sections may coexist. Yikes!
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bool is64_bit;
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std::string_view data;
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};
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// Abbreviation for a Debugging Information Entry.
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struct DIEAbbreviation
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{
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uint64_t code = 0;
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uint64_t tag = 0;
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bool has_children = false;
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std::string_view attributes;
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};
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// Debugging information entry to define a low-level representation of a
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// source program. Each debugging information entry consists of an identifying
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// tag and a series of attributes. An entry, or group of entries together,
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// provide a description of a corresponding entity in the source program.
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struct Die
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{
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bool is64Bit; /// NOLINT
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// Offset from start to first attribute
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uint8_t attr_offset;
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// Offset within debug info.
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uint64_t offset;
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uint64_t code;
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DIEAbbreviation abbr;
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};
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struct AttributeSpec
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{
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uint64_t name = 0;
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uint64_t form = 0;
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int64_t implicitConst = 0; // only set when form=DW_FORM_implicit_const
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explicit operator bool() const { return name != 0 || form != 0; }
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};
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struct Attribute
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{
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AttributeSpec spec;
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const Die & die;
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std::variant<uint64_t, std::string_view> attr_value;
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};
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enum
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{
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DW_UT_compile = 0x01,
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DW_UT_skeleton = 0x04,
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};
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struct CompilationUnit
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{
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bool is64Bit = false; /// NOLINT
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uint8_t version = 0;
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uint8_t unit_type = DW_UT_compile; // DW_UT_compile or DW_UT_skeleton
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uint8_t addr_size = 0;
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// Offset in .debug_info of this compilation unit.
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uint64_t offset = 0;
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uint64_t size = 0;
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// Offset in .debug_info for the first DIE in this compilation unit.
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uint64_t first_die = 0;
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uint64_t abbrev_offset = 0;
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// The beginning of the CU's contribution to .debug_addr
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std::optional<uint64_t> addr_base; // DW_AT_addr_base (DWARF 5)
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// The beginning of the offsets table (immediately following the
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// header) of the CU's contribution to .debug_loclists
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std::optional<uint64_t> loclists_base; // DW_AT_loclists_base (DWARF 5)
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// The beginning of the offsets table (immediately following the
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// header) of the CU's contribution to .debug_rnglists
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std::optional<uint64_t> rnglists_base; // DW_AT_rnglists_base (DWARF 5)
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// Points to the first string offset of the compilation unit’s
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// contribution to the .debug_str_offsets (or .debug_str_offsets.dwo) section.
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std::optional<uint64_t> str_offsets_base; // DW_AT_str_offsets_base (DWARF 5)
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// Only the CompilationUnit that contains the caller functions needs this cache.
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// Indexed by (abbr.code - 1) if (abbr.code - 1) < abbrCache.size();
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std::vector<DIEAbbreviation> abbr_cache;
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};
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/** cu must exist during the life cycle of created Die. */
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Die getDieAtOffset(const CompilationUnit & cu, uint64_t offset) const;
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bool findLocation(
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uintptr_t address,
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LocationInfoMode mode,
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CompilationUnit & cu,
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LocationInfo & info,
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std::vector<SymbolizedFrame> & inline_frames,
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bool assume_in_cu_range) const;
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/**
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* Finds a subprogram debugging info entry that contains a given address among
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* children of given die. Depth first search.
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*/
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void findSubProgramDieForAddress(
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const CompilationUnit & cu, const Die & die, uint64_t address, std::optional<uint64_t> base_addr_cu, Die & subprogram) const;
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// Interpreter for the line number bytecode VM
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class LineNumberVM
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{
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public:
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LineNumberVM(
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std::string_view data,
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std::string_view compilationDirectory,
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std::string_view debugStr,
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std::string_view debugLineStr);
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bool findAddress(uintptr_t target, Path & file, uint64_t & line);
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/** Gets full file name at given index including directory. */
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Path getFullFileName(uint64_t index) const;
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private:
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void init();
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void reset();
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// Execute until we commit one new row to the line number matrix
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bool next(std::string_view & program);
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enum StepResult
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{
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CONTINUE, // Continue feeding opcodes
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COMMIT, // Commit new <address, file, line> tuple
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END, // End of sequence
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};
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// Execute one opcode
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StepResult step(std::string_view & program);
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struct FileName
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{
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std::string_view relativeName; /// NOLINT
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// 0 = current compilation directory
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// otherwise, 1-based index in the list of include directories
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uint64_t directoryIndex; /// NOLINT
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};
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// Read one FileName object, remove_prefix program
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static bool readFileName(std::string_view & program, FileName & fn);
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// Get file name at given index; may be in the initial table
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// (fileNames_) or defined using DW_LNE_define_file (and we reexecute
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// enough of the program to find it, if so)
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FileName getFileName(uint64_t index) const;
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// Get include directory at given index
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std::string_view getIncludeDirectory(uint64_t index) const;
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// Execute opcodes until finding a DW_LNE_define_file and return true;
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// return file at the end.
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bool nextDefineFile(std::string_view & program, FileName & fn) const;
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// Initialization
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bool is64Bit_; /// NOLINT
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std::string_view data_; /// NOLINT
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std::string_view compilationDirectory_; /// NOLINT
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std::string_view debugStr_; // needed for DWARF 5 /// NOLINT
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std::string_view debugLineStr_; // DWARF 5 /// NOLINT
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// Header
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uint16_t version_; /// NOLINT
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uint8_t minLength_; /// NOLINT
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bool defaultIsStmt_; /// NOLINT
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int8_t lineBase_; /// NOLINT
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uint8_t lineRange_; /// NOLINT
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uint8_t opcodeBase_; /// NOLINT
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const uint8_t * standardOpcodeLengths_; /// NOLINT
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// 6.2.4 The Line Number Program Header.
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struct
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{
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size_t includeDirectoryCount;
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std::string_view includeDirectories;
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size_t fileNameCount;
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std::string_view fileNames;
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} v4_;
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struct
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{
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uint8_t directoryEntryFormatCount;
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std::string_view directoryEntryFormat;
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uint64_t directoriesCount;
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std::string_view directories;
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uint8_t fileNameEntryFormatCount;
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std::string_view fileNameEntryFormat;
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uint64_t fileNamesCount;
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std::string_view fileNames;
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} v5_;
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// State machine registers
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uint64_t address_; /// NOLINT
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uint64_t file_; /// NOLINT
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uint64_t line_; /// NOLINT
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uint64_t column_; /// NOLINT
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bool isStmt_; /// NOLINT
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bool basicBlock_; /// NOLINT
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bool endSequence_; /// NOLINT
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bool prologueEnd_; /// NOLINT
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bool epilogueBegin_; /// NOLINT
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uint64_t isa_; /// NOLINT
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uint64_t discriminator_; /// NOLINT
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};
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/**
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* Finds inlined subroutine DIEs and their caller lines that contains a given
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* address among children of given die. Depth first search.
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*/
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void findInlinedSubroutineDieForAddress(
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const CompilationUnit & cu,
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const Die & die,
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const LineNumberVM & line_vm,
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uint64_t address,
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std::optional<uint64_t> base_addr_cu,
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std::vector<CallLocation> & locations,
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size_t max_size) const;
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// Read an abbreviation from a std::string_view, return true if at end; remove_prefix section
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static bool readAbbreviation(std::string_view & section, DIEAbbreviation & abbr);
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static void readCompilationUnitAbbrs(std::string_view abbrev, CompilationUnit & cu);
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/**
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* Iterates over all children of a debugging info entry, calling the given
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* callable for each. Iteration is stopped early if any of the calls return
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* false. Returns the offset of next DIE after iterations.
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*/
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size_t forEachChild(const CompilationUnit & cu, const Die & die, std::function<bool(const Die & die)> f) const;
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// Get abbreviation corresponding to a code, in the chunk starting at
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// offset in the .debug_abbrev section
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DIEAbbreviation getAbbreviation(uint64_t code, uint64_t offset) const;
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/**
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* Iterates over all attributes of a debugging info entry, calling the given
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* callable for each. If all attributes are visited, then return the offset of
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* next DIE, or else iteration is stopped early and return size_t(-1) if any
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* of the calls return false.
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*/
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size_t forEachAttribute(const CompilationUnit & cu, const Die & die, std::function<bool(const Attribute & die)> f) const;
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Attribute readAttribute(
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const CompilationUnit & cu,
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const Die & die,
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AttributeSpec spec,
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std::string_view & info) const;
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// Read one attribute <name, form> pair, remove_prefix sp; returns <0, 0> at end.
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static AttributeSpec readAttributeSpec(std::string_view & sp);
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// Read one attribute value, remove_prefix sp
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using AttributeValue = std::variant<uint64_t, std::string_view>;
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AttributeValue readAttributeValue(std::string_view & sp, uint64_t form, bool is64_bit) const;
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// Get an ELF section by name, return true if found
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std::string_view getSection(const char * name) const;
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CompilationUnit getCompilationUnit(uint64_t offset) const;
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// Finds the Compilation Unit starting at offset.
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CompilationUnit findCompilationUnit(uint64_t targetOffset) const;
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// Parses an attribute of "reference" form class, i.e. a reference to another DIE.
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// Returns the unit containing the target DIE (nullopt if it's in the same unit as the source DIE)
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// and the offset of the target DIE (relative to .debug_info, not to unit).
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std::optional<std::pair<std::optional<CompilationUnit>, uint64_t>> getReferenceAttribute(
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const CompilationUnit & cu, const Die & die, uint64_t attr_name) const;
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// Check if the given address is in the range list at the given offset in .debug_ranges.
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bool isAddrInRangeList(
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const CompilationUnit & cu,
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uint64_t address,
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std::optional<uint64_t> base_addr,
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size_t offset,
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uint8_t addr_size) const;
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std::string_view abbrev_; // .debug_abbrev /// NOLINT
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std::string_view addr_; // .debug_addr (DWARF 5) /// NOLINT
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std::string_view aranges_; // .debug_aranges /// NOLINT
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std::string_view info_; // .debug_info /// NOLINT
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std::string_view line_; // .debug_line /// NOLINT
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std::string_view line_str_; // .debug_line_str (DWARF 5) /// NOLINT
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std::string_view loclists_; // .debug_loclists (DWARF 5) /// NOLINT
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std::string_view ranges_; // .debug_ranges /// NOLINT
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std::string_view rnglists_; // .debug_rnglists (DWARF 5) /// NOLINT
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std::string_view str_; // .debug_str /// NOLINT
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std::string_view str_offsets_; // .debug_str_offsets (DWARF 5) /// NOLINT
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};
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}
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#endif
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