Cpptrace

Cpptrace is a simple, portable, and self-contained C++ stacktrace library supporting C++11 and greater on Linux, macOS, and Windows including MinGW and Cygwin environments. The goal: Make stack traces simple for once.

Cpptrace also has a C API, docs here.

Table of Contents

• 30-Second Overview
  • CMake FetchContent Usage
• FAQ
  • What about C++23 <stacktrace>?
  • What does cpptrace have over other C++ stacktrace libraries?
• In-Depth Documentation
  • Prerequisites
  • namespace cpptrace
    • Stack Traces
    • Object Traces
    • Raw Traces
    • Utilities
    • Configuration
    • Traced Exceptions
  • Wrapping std::exceptions
  • Exception handling with cpptrace
  • Signal-Safe Tracing
  • Utility Types
• Supported Debug Formats
• Usage
  • CMake FetchContent
  • System-Wide Installation
  • Local User Installation
  • Use Without CMake
  • Installation Without Package Managers or FetchContent
  • Package Managers
    • Conan
    • Vcpkg
• Platform Logistics
  • Windows
  • macOS
• Library Back-Ends
  • Summary of Library Configurations
• Testing Methodology
• Notes About the Library and Future Work
• License

30-Second Overview

Generating stack traces is as easy as:

#include <cpptrace/cpptrace.hpp>

void trace() {
    cpptrace::generate_trace().print();
}

Cpptrace can also retrieve function inlining information on optimized release builds:

Cpptrace provides access to resolved stack traces as well as lightweight raw traces (just addresses) that can be resolved later:

const auto raw_trace = cpptrace::generate_raw_trace();
// then later
raw_trace.resolve().print();

Cpptrace also provides exception types that store stack traces:

#include <cpptrace/cpptrace.hpp>

void trace() {
    throw cpptrace::logic_error("This wasn't supposed to happen!");
}

Additional notable features:

• Utilities for demangling
• Utilities for catching std::exceptions and wrapping them in traced exceptions
• Signal-safe stack tracing
• Source code snippets in traces

CMake FetchContent Usage

include(FetchContent)
FetchContent_Declare(
  cpptrace
  GIT_REPOSITORY https://github.com/jeremy-rifkin/cpptrace.git
  GIT_TAG        v0.5.2 # <HASH or TAG>
)
FetchContent_MakeAvailable(cpptrace)
target_link_libraries(your_target cpptrace::cpptrace)

# On windows copy cpptrace.dll to the same directory as the executable for your_target
if(WIN32)
  add_custom_command(
    TARGET your_target POST_BUILD
    COMMAND ${CMAKE_COMMAND} -E copy_if_different
    $<TARGET_FILE:cpptrace::cpptrace>
    $<TARGET_FILE_DIR:your_target>
  )
endif()

Be sure to configure with -DCMAKE_BUILD_TYPE=Debug or -DDCMAKE_BUILD_TYPE=RelWithDebInfo for symbols and line information.

On macOS it is recommended to generate a .dSYM file, see Platform Logistics below.

For other ways to use the library, such as through package managers, a system-wide installation, or on a platform without internet access see Usage below.

FAQ

What about C++23 <stacktrace>?

Some day C++23's <stacktrace> will be ubiquitous. And maybe one day the msvc implementation will be acceptable. The original motivation for cpptrace was to support projects using older C++ standards and as the library has grown its functionality has extended beyond the standard library's implementation.

Cpptrace provides functionality beyond what the standard library provides and what implementations provide, such as:

• Walking inlined function calls
• Providing a lightweight interface for "raw traces"
• Resolving function parameter types
• Providing traced exception objects
• Providing an API for signal-safe stacktrace generation

What does cpptrace have over other C++ stacktrace libraries?

Other C++ stacktrace libraries, such as boost stacktrace and backward-cpp, fall short when it comes to portability and ease of use. In testing, I found neither to provide adaquate coverage of various environments. Even when they can be made to work in an environment they require manual configuration from the end-user, possibly requiring manual installation of third-party dependencies. This is a highly undesirable burden to impose on users, especially when it is for a software package which just provides diagnostics as opposed to core functionality. Additionally, cpptrace provides support for resolving inlined calls by default for DWARF symbols (boost does not do this, backward-cpp can do this but only for some back-ends), better support for resolving full function signatures, and nicer API, among other features.

In-Depth Documentation

Prerequisites

[!IMPORTANT] Debug info (-g//Z7//Zi//DEBUG/-DBUILD_TYPE=Debug/-DBUILD_TYPE=RelWithDebInfo) is required for complete trace information.

namespace cpptrace

cpptrace::generate_trace() can be used to generate a stacktrace object at the current call site. Resolved frames can be accessed from this object with .frames and also the trace can be printed with .print(). Cpptrace also provides a method to get lightweight raw traces, which are just vectors of program counters, which can be resolved at a later time.

All functions are thread-safe unless otherwise noted.

Stack Traces

The core resolved stack trace object. Generate a trace with cpptrace::generate_trace() or cpptrace::stacktrace::current(). On top of a set of helper functions struct stacktrace allows direct access to frames as well as iterators.

cpptrace::stacktrace::print can be used to print a stacktrace. cpptrace::stacktrace::print_with_snippets can be used to print a stack trace with source code snippets.

namespace cpptrace {
    // Some type sufficient for an instruction pointer, currently always an alias to std::uintptr_t
    using frame_ptr = std::uintptr_t;

    struct stacktrace_frame {
        frame_ptr raw_address; // address in memory
        frame_ptr object_address; // address in the object file
        // nullable<T> represents a nullable integer. More docs later.
        nullable<std::uint32_t> line;
        nullable<std::uint32_t> column;
        std::string filename;
        std::string symbol;
        bool is_inline;
        bool operator==(const stacktrace_frame& other) const;
        bool operator!=(const stacktrace_frame& other) const;
        object_frame get_object_info() const; // object_address is stored but if the object_path is needed this can be used
        std::string to_string() const;
        /* operator<<(ostream, ..) and std::format support exist for this object */
    };

    struct stacktrace {
        std::vector<stacktrace_frame> frames;
        // here as a drop-in for std::stacktrace
        static stacktrace current(std::size_t skip = 0);
        static stacktrace current(std::size_t skip, std::size_t max_depth);
        void print() const;
        void print(std::ostream& stream) const;
        void print(std::ostream& stream, bool color) const;
        void print_with_snippets() const;
        void print_with_snippets(std::ostream& stream) const;
        void print_with_snippets(std::ostream& stream, bool color) const;
        std::string to_string(bool color = false) const;
        void clear();
        bool empty() const noexcept;
        /* operator<<(ostream, ..), std::format support, and iterators exist for this object */
    };

    stacktrace generate_trace(std::size_t skip = 0);
    stacktrace generate_trace(std::size_t skip, std::size_t max_depth);
}

Object Traces

Object traces contain the most basic information needed to construct a stack trace outside the currently running executable. It contains the raw address, the address in the binary (ASLR and the object file's memory space and whatnot is resolved), and the path to the object the instruction pointer is located in.

namespace cpptrace {
    struct object_frame {
        std::string object_path;
        frame_ptr raw_address;
        frame_ptr object_address;
    };

    struct object_trace {
        std::vector<object_frame> frames;
        static object_trace current(std::size_t skip = 0);
        static object_trace current(std::size_t skip, std::size_t max_depth);
        stacktrace resolve() const;
        void clear();
        bool empty() const noexcept;
        /* iterators exist for this object */
    };

    object_trace generate_object_trace(std::size_t skip = 0);
    object_trace generate_object_trace(std::size_t skip, std::size_t max_depth);
}

Raw Traces

Raw trace access: A vector of program counters. These are ideal for fast and cheap traces you want to resolve later.

Note it is important executables and shared libraries in memory aren't somehow unmapped otherwise libdl calls (and GetModuleFileName in windows) will fail to figure out where the program counter corresponds to.

namespace cpptrace {
    struct raw_trace {
        std::vector<frame_ptr> frames;
        static raw_trace current(std::size_t skip = 0);
        static raw_trace current(std::size_t skip, std::size_t max_depth);
        object_trace resolve_object_trace() const;
        stacktrace resolve() const;
        void clear();
        bool empty() const noexcept;
        /* iterators exist for this object */
    };

    raw_trace generate_raw_trace(std::size_t skip = 0);
    raw_trace generate_raw_trace(std::size_t skip, std::size_t max_depth);
}

Utilities

cpptrace::demangle provides a helper function for name demangling, since it has to implement that helper internally anyways.

cpptrace::get_snippet gets a text snippet, if possible, from for the given source file for +/- context_size lines around line.

cpptrace::isatty and the fileno definitions are useful for deciding whether to use color when printing stack traces.

cpptrace::register_terminate_handler() is a helper function to set a custom std::terminate handler that prints a stack trace from a cpptrace exception (more info below) and otherwise behaves like the normal terminate handler.

namespace cpptrace {
    std::string demangle(const std::string& name);
    std::string get_snippet(
        const std::string& path,
        std::size_t line,
        std::size_t context_size,
        bool color = false
    );
    bool isatty(int fd);

    extern const int stdin_fileno;
    extern const int stderr_fileno;
    extern const int stdout_fileno;

    void register_terminate_handler();
}

Configuration

cpptrace::absorb_trace_exceptions: Configure whether the library silently absorbs internal exceptions and continues. Default is true.

cpptrace::ctrace_enable_inlined_call_resolution: Configure whether the library will attempt to resolve inlined call information for release builds. Default is true.

cpptrace::experimental::set_cache_mode: Control time-memory tradeoffs within the library. By default speed is prioritized. If using this function, set the cache mode at the very start of your program before any traces are performed.

namespace cpptrace {
    void absorb_trace_exceptions(bool absorb);
    void ctrace_enable_inlined_call_resolution(bool enable);

    enum class cache_mode {
        // Only minimal lookup tables
        prioritize_memory,
        // Build lookup tables but don't keep them around between trace calls
        hybrid,
        // Build lookup tables as needed
        prioritize_speed
    };

    namespace experimental {
        void set_cache_mode(cache_mode mode);
    }
}

Traced Exceptions

Cpptrace provides an interface for a traced exceptions, cpptrace::exception, as well as a set of exception classes that that generate stack traces when thrown. These exceptions generate relatively lightweight raw traces and resolve symbols and line numbers lazily if and when requested.

The basic interface is:

namespace cpptrace {
    class exception : public std::exception {
    public:
        virtual const char* what() const noexcept = 0; // The what string both the message and trace
        virtual const char* message() const noexcept = 0;
        virtual const stacktrace& trace() const noexcept = 0;
    };
}

There are two ways to go about traced exception objects: Traces can be resolved eagerly or lazily. Cpptrace provides the basic implementation of exceptions as lazy exceptions. I hate to have anything about the implementation exposed in the interface or type system but this seems to be the best way to do this.

namespace cpptrace {
    class lazy_exception : public exception {
        // lazy_trace_holder is basically a std::variant<raw_trace, stacktrace>, more docs later
        mutable detail::lazy_trace_holder trace_holder;
        mutable std::string what_string;
    public:
        explicit lazy_exception(
            raw_trace&& trace = detail::get_raw_trace_and_absorb()
        ) noexcept : trace_holder(std::move(trace)) {}
        const char* what() const noexcept override;
        const char* message() const noexcept override;
        const stacktrace& trace() const noexcept override;
    };
}

cpptrace::lazy_exception can be freely thrown or overridden. Generally message() is the only field to override.

Lastly cpptrace provides an exception class that takes a user-provided message, cpptrace::exception_with_message, as well as a number of traced exception classes resembling <stdexcept>:

namespace cpptrace {
    class exception_with_message : public lazy_exception {
        mutable std::string user_message;
    public:
        explicit exception_with_message(
            std::string&& message_arg,
            raw_trace&& trace = detail::get_raw_trace_and_absorb()
        ) noexcept : lazy_exception(std::move(trace)), user_message(std::move(message_arg)) {}
        const char* message() const noexcept override;
    };

    // All stdexcept errors have analogs here. All have the constructor:
    // explicit the_error(
    //     std::string&& message_arg,
    //     raw_trace&& trace = detail::get_raw_trace_and_absorb()
    // ) noexcept
    //     : exception_with_message(std::move(message_arg), std::move(trace)) {}
    class logic_error      : public exception_with_message { ... };
    class domain_error     : public exception_with_message { ... };
    class invalid_argument : public exception_with_message { ... };
    class length_error     : public exception_with_message { ... };
    class out_of_range     : public exception_with_message { ... };
    class runtime_error    : public exception_with_message { ... };
    class range_error      : public exception_with_message { ... };
    class overflow_error   : public exception_with_message { ... };
    class underflow_error  : public exception_with_message { ... };
}

Wrapping std::exceptions

Cpptrace exceptions can provide great information for user-controlled exceptions. For non-cpptrace::exceptions that may originate outside of code you control, e.g. the standard library, cpptrace provides some wrapper utilities that can rethrow these exceptions nested in traced cpptrace exceptions. The trace won't be perfect, the trace will start where the rapper caught it, but these utilities can provide good diagnostic information. Unfortunately this is the best solution for this problem, as far as I know.

std::vector<int> foo = {1, 2, 3};
CPPTRACE_WRAP_BLOCK(
    foo.at(4) = 2;
    foo.at(5)++;
);
std::cout<<CPPTRACE_WRAP(foo.at(12))<<std::endl;

Exception handling with cpptrace

Working with cpptrace exceptions in your code:

try {
    foo();
} catch(cpptrace::exception& e) {
    // Prints the exception info and stack trace, conditionally enabling color codes depending on
    // whether stderr is a terminal
    std::cerr << "Error: " << e.message() << '\n';
    e.trace().print(std::cerr, cpptrace::isatty(cpptrace::stderr_fileno));
} catch(std::exception& e) {
    std::cerr << "Error: " << e.what() << '\n';
}

Additionally cpptrace provides a custom std::terminate handler that prints a stack trace from a cpptrace exception and otherwise behaves like the normal terminate handler and prints the stack trace involved in reaching std::terminate. The stack trace to std::terminate may be helpful or it may not, it depends on the implementation, but often if an implementation can't find an appropriate catch while unwinding it will jump directly to std::terminate giving good information.

To register this custom handler:

cpptrace::register_terminate_handler();

Signal-Safe Tracing

Signal-safe stack tracing is very useful for debugging application crashes, e.g. SIGSEGVs or SIGTRAPs, but it's very difficult to do correctly and most implementations I see online do this incorrectly.

In order to do this full process safely the way to go is collecting basic information in the signal handler and then either resolving later or handing that information to another process to resolve.

It's not as simple as calling cpptrace::generate_trace().print(), though you might be able to get away with that, but this is what is needed to really do this safely.

The safe API is as follows:

namespace cpptrace {
    std::size_t safe_generate_raw_trace(frame_ptr* buffer, std::size_t size, std::size_t skip = 0);
    std::size_t safe_generate_raw_trace(frame_ptr* buffer, std::size_t size, std::size_t skip, std::size_t max_depth);
    struct safe_object_frame {
        frame_ptr raw_address;
        frame_ptr address_relative_to_object_start; // object base address must yet be added
        char object_path[CPPTRACE_PATH_MAX + 1];
        object_frame resolve() const; // To be called outside a signal handler. Not signal safe.
    };
    void get_safe_object_frame(frame_ptr address, safe_object_frame* out);
    bool can_signal_safe_unwind();
}

[!IMPORTANT] Currently signal-safe stack unwinding is only possible with libunwind, which must be manually enabled. If signal-safe unwinding isn't supported, safe_generate_raw_trace will just produce an empty trace. can_signal_safe_unwind can be used to check for signal-safe unwinding support. If object information can't be resolved in a signal-safe way then get_safe_object_frame will not populate fields beyond the raw_address.

[!CAUTION] Calls to shared objects can be lazy-loaded where the first call to the shared object invokes non-signal-safe functions such as malloc(). To avoid this, call these routines in main() ahead of a signal handler to "warm up" the library.

Because signal-safe tracing is an involved process, I have written up a comprehensive overview of what is involved at signal-safe-tracing.md.

Utility Types

A couple utility types are used to provide the library with a good interface.

nullable<T> is used for a nullable integer type. Internally the maximum value for T is used as a sentinel. std::optional would be used if this library weren't c++11. But, nullable<T> provides an std::optional-like interface and it's less heavy-duty for this use than an std::optional.

detail::lazy_trace_holder is a utility type for lazy_exception used in place of an std::variant<raw_trace, stacktrace>.

namespace cpptrace {
    template<typename T, typename std::enable_if<std::is_integral<T>::value, int>::type = 0>
    struct nullable {
        T raw_value;
        nullable& operator=(T value)
        bool has_value() const noexcept;
        T& value() noexcept;
        const T& value() const noexcept;
        T value_or(T alternative) const noexcept;
        void swap(nullable& other) noexcept;
        void reset() noexcept;
        bool operator==(const nullable& other) const noexcept;
        bool operator!=(const nullable& other) const noexcept;
        constexpr static nullable null() noexcept; // returns a null instance
    };

    namespace detail {
        class lazy_trace_holder {
            bool resolved;
            union {
                raw_trace trace;
                stacktrace resolved_trace;
            };
        public:
            // constructors
            lazy_trace_holder() : trace() {}
            explicit lazy_trace_holder(raw_trace&& _trace);
            explicit lazy_trace_holder(stacktrace&& _resolved_trace);
            // logistics
            lazy_trace_holder(const lazy_trace_holder& other);
            lazy_trace_holder(lazy_trace_holder&& other) noexcept;
            lazy_trace_holder& operator=(const lazy_trace_holder& other);
            lazy_trace_holder& operator=(lazy_trace_holder&& other) noexcept;
            ~lazy_trace_holder();
            // access
            stacktrace& get_resolved_trace();
            const stacktrace& get_resolved_trace() const; // throws if not already resolved
        private:
            void clear();
        };
    }
}

Supported Debug Formats

DWARF5 added DWARF package files. As far as I can tell no compiler implements these yet.

Usage

CMake FetchContent

With CMake FetchContent:

include(FetchContent)
FetchContent_Declare(
  cpptrace
  GIT_REPOSITORY https://github.com/jeremy-rifkin/cpptrace.git
  GIT_TAG        v0.5.2 # <HASH or TAG>
)
FetchContent_MakeAvailable(cpptrace)
target_link_libraries(your_target cpptrace::cpptrace)

It's as easy as that. Cpptrace will automatically configure itself for your system. Note: On windows and macos some extra work is required, see Platform Logistics below.

Be sure to configure with -DCMAKE_BUILD_TYPE=Debug or -DDCMAKE_BUILD_TYPE=RelWithDebInfo for symbols and line information.

System-Wide Installation

git clone https://github.com/jeremy-rifkin/cpptrace.git
git checkout v0.5.2
mkdir cpptrace/build
cd cpptrace/build
cmake .. -DCMAKE_BUILD_TYPE=Release
make -j
sudo make install

Using through cmake:

find_package(cpptrace REQUIRED)
target_link_libraries(<your target> cpptrace::cpptrace)

Be sure to configure with -DCMAKE_BUILD_TYPE=Debug or -DDCMAKE_BUILD_TYPE=RelWithDebInfo for symbols and line information.

Or compile with -lcpptrace:

g++ main.cpp -o main -g -Wall -lcpptrace
./main

If you get an error along the lines of

error while loading shared libraries: libcpptrace.so: cannot open shared object file: No such file or directory

You may have to run sudo /sbin/ldconfig to create any necessary links and update caches so the system can find libcpptrace.so (I had to do this on Ubuntu). Only when installing system-wide. Usually your package manger does this for you when installing new libraries.

git clone https://github.com/jeremy-rifkin/cpptrace.git
git checkout v0.5.2
mkdir cpptrace/build
cd cpptrace/build
cmake .. -DCMAKE_BUILD_TYPE=Release
msbuild cpptrace.sln
msbuild INSTALL.vcxproj

Local User Installation

To install just for the local user (or any custom prefix):

git clone https://github.com/jeremy-rifkin/cpptrace.git
git checkout v0.5.2
mkdir cpptrace/build
cd cpptrace/build
cmake .. -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=$HOME/wherever
make -j
sudo make install

Using through cmake:

find_package(cpptrace REQUIRED PATHS $ENV{HOME}/wherever)
target_link_libraries(<your target> cpptrace::cpptrace)

Using manually:

g++ main.cpp -o main -g -Wall -I$HOME/wherever/include -L$HOME/wherever/lib -lcpptrace

Use Without CMake

To use the library without cmake first follow the installation instructions at System-Wide Installation, Local User Installation, or Package Managers.

In addition to any include or library paths you'll need to specify to tell the compiler where cpptrace was installed. The typical dependencies for cpptrace are:

Note: Newer libdwarf requires -lzstd, older libdwarf does not.

[!IMPORTANT] If you are linking statically, you will additionally need to specify -DCPPTRACE_STATIC_DEFINE.

Dependencies may differ if different back-ends are manually selected.

Installation Without Package Managers or FetchContent

Some users may prefer, or need to, to install cpptrace without package managers or fetchcontent (e.g. if their system does not have internet access). Below are instructions for how to install libdwarf and cpptrace.

mkdir -p ~/scratch/cpptrace-test/resources

cd ~/scratch/cpptrace-test
git clone https://github.com/facebook/zstd.git
cd zstd
git checkout 63779c798237346c2b245c546c40b72a5a5913fe
cd build/cmake
mkdir build
cd build
cmake .. -DCMAKE_INSTALL_PREFIX=~/scratch/cpptrace-test/resources -DZSTD_BUILD_PROGRAMS=On -DZSTD_BUILD_CONTRIB=On -DZSTD_BUILD_TESTS=On -DZSTD_BUILD_STATIC=On -DZSTD_BUILD_SHARED=On -DZSTD_LEGACY_SUPPORT=On
make -j
make install

cd ~/scratch/cpptrace-test
git clone https://github.com/jeremy-rifkin/libdwarf-lite.git
cd libdwarf-lite
git checkout 5c0cb251f94b27e90184e6b2d9a0c9c62593babc
mkdir build
cd build
cmake .. -DPIC_ALWAYS=On -DBUILD_DWARFDUMP=Off -DCMAKE_PREFIX_PATH=~/scratch/cpptrace-test/resources -DCMAKE_INSTALL_PREFIX=~/scratch/cpptrace-test/resources
make -j
make install

cd ~/scratch/cpptrace-test
git clone https://github.com/jeremy-rifkin/cpptrace.git
cd cpptrace
git checkout v0.5.2
mkdir build
cd build
cmake .. -DCMAKE_BUILD_TYPE=Release -DBUILD_SHARED_LIBS=On -DCPPTRACE_USE_EXTERNAL_LIBDWARF=On -DCMAKE_PREFIX_PATH=~/scratch/cpptrace-test/resources -DCMAKE_INSTALL_PREFIX=~/scratch/cpptrace-test/resources
make -j
make install

Package Managers

Conan

Cpptrace is available through conan at https://conan.io/center/recipes/cpptrace.

[requires]
cpptrace/0.5.2
[generators]
CMakeDeps
CMakeToolchain
[layout]
cmake_layout

# ...
find_package(cpptrace REQUIRED)
# ...
target_link_libraries(YOUR_TARGET cpptrace::cpptrace)

Vcpkg

vcpkg install cpptrace

find_package(cpptrace CONFIG REQUIRED)
target_link_libraries(main PRIVATE cpptrace::cpptrace)

Platform Logistics

Windows and macOS require a little extra work to get everything in the right place.

Windows

Copying the library .dll on Windows:

# Copy the cpptrace.dll on windows to the same directory as the executable for your_target.
# Not required if static linking.
if(WIN32)
  add_custom_command(
    TARGET your_target POST_BUILD
    COMMAND ${CMAKE_COMMAND} -E copy_if_different
    $<TARGET_FILE:cpptrace::cpptrace>
    $<TARGET_FILE_DIR:your_target>
  )
endif()

macOS

On macOS, it is recommended to generate a dSYM file containing debug information for your program. This is not required as cpptrace makes a good effort at finding and reading the debug information without this, but having a dSYM file is the most robust method.

When using Xcode with CMake, this can be done with:

set_target_properties(your_target PROPERTIES XCODE_ATTRIBUTE_DEBUG_INFORMATION_FORMAT "dwarf-with-dsym")

Outside of Xcode, this can be done with dsymutil yourbinary:

# Create a .dSYM file on macOS
if(APPLE)
  add_custom_command(
    TARGET your_target
    POST_BUILD
    COMMAND dsymutil $<TARGET_FILE:your_target>
  )
endif()

Library Back-Ends

Cpptrace supports a number of back-ends to produce stack traces. Stack traces are produced in roughly three steps: Unwinding, symbol resolution, and demangling.

The library's CMake automatically configures itself for what your system supports. The ideal configuration is as follows:

Support for these back-ends is the main development focus and they should work well. If you want to use a different back-end such as addr2line, for example, you can configure the library to do so.

Unwinding

Some back-ends (execinfo and CaptureStackBackTrace) require a fixed buffer has to be created to read addresses into while unwinding. By default the buffer can hold addresses for 200 frames (beyond the skip frames). This is configurable with CPPTRACE_HARD_MAX_FRAMES.

Symbol resolution

*: Requires installation

One back-end should be used. For MinGW CPPTRACE_GET_SYMBOLS_WITH_LIBDWARF and CPPTRACE_GET_SYMBOLS_WITH_DBGHELP can be used in conjunction.

Note for addr2line: By default cmake will resolve an absolute path to addr2line to bake into the library. This path can be configured with CPPTRACE_ADDR2LINE_PATH, or CPPTRACE_ADDR2LINE_SEARCH_SYSTEM_PATH can be used to have the library search the system path for addr2line at runtime. This is not the default to prevent against path injection attacks.

Demangling

Lastly, depending on other back-ends used a demangler back-end may be needed.

More?

There are plenty more libraries that can be used for unwinding, parsing debug information, and demangling. In the future more back-ends can be added. Ideally this library can "just work" on systems, without additional installation work.

Summary of Library Configurations

Summary of all library configuration options:

Back-ends:

• CPPTRACE_GET_SYMBOLS_WITH_LIBDWARF=On/Off
• CPPTRACE_GET_SYMBOLS_WITH_DBGHELP=On/Off
• CPPTRACE_GET_SYMBOLS_WITH_LIBBACKTRACE=On/Off
• CPPTRACE_GET_SYMBOLS_WITH_ADDR2LINE=On/Off
• CPPTRACE_GET_SYMBOLS_WITH_LIBDL=On/Off
• CPPTRACE_GET_SYMBOLS_WITH_NOTHING=On/Off
• CPPTRACE_UNWIND_WITH_UNWIND=On/Off
• CPPTRACE_UNWIND_WITH_LIBUNWIND=On/Off
• CPPTRACE_UNWIND_WITH_EXECINFO=On/Off
• CPPTRACE_UNWIND_WITH_WINAPI=On/Off
• CPPTRACE_UNWIND_WITH_DBGHELP=On/Off
• CPPTRACE_UNWIND_WITH_NOTHING=On/Off
• CPPTRACE_DEMANGLE_WITH_CXXABI=On/Off
• CPPTRACE_DEMANGLE_WITH_WINAPI=On/Off
• CPPTRACE_DEMANGLE_WITH_NOTHING=On/Off

Back-end configuration:

• CPPTRACE_BACKTRACE_PATH=<string>: Path to libbacktrace backtrace.h, needed when compiling with clang/
• CPPTRACE_HARD_MAX_FRAMES=<number>: Some back-ends write to a fixed-size buffer. This is the size of that buffer. Default is 200.
• CPPTRACE_ADDR2LINE_PATH=<string>: Specify the absolute path to the addr2line binary for cpptrace to invoke. By default the config script will search for a binary and use that absolute path (this is to prevent against path injection).
• CPPTRACE_ADDR2LINE_SEARCH_SYSTEM_PATH=On/Off: Specifies whether cpptrace should let the system search the PATH environment variable directories for the binary.

Other useful configurations:

• CPPTRACE_BUILD_SHARED=On/Off: Override for BUILD_SHARED_LIBS.
• CPPTRACE_INCLUDES_WITH_SYSTEM=On/Off: Marks cpptrace headers as SYSTEM which will hide any warnings that aren't the fault of your project. Defaults to On.
• CPPTRACE_INSTALL_CMAKEDIR: Override for the installation path for the cmake configs.
• CPPTRACE_USE_EXTERNAL_LIBDWARF=On/Off: Get libdwarf from find_package rather than FetchContent.
• CPPTRACE_POSITION_INDEPENDENT_CODE=On/Off: Compile the library as a position independent code (PIE). Defaults to On.

Testing:

• CPPTRACE_BUILD_TESTING Build small demo and test program
• CPPTRACE_BUILD_TEST_RDYNAMIC Use -rdynamic when compiling the test program

Testing Methodology

Cpptrace currently uses integration and functional testing, building and running under every combination of back-end options. The implementation is based on github actions matrices and driven by python scripts located in the ci/ folder. Testing used to be done by github actions matrices directly, however, launching hundreds of two second jobs was extremely inefficient. Test outputs are compared against expected outputs located in test/expected/. Stack trace addresses may point to the address after an instruction depending on the unwinding back-end, and the python script will check for an exact or near-match accordingly.

Notes About the Library and Future Work

For the most part I'm happy with the state of the library. But I'm sure that there is room for improvement and issues will exist. If you encounter any issue, please let me know! If you find any pain-points in the library, please let me know that too.

A note about performance: For handling of DWARF symbols there is a lot of room to explore for performance optimizations and time-memory tradeoffs. If you find the current implementation is either slow or using too much memory, I'd be happy to explore some of these options.

A couple things I'd like to improve in the future:

• On Windows when collecting symbols with dbghelp (msvc/clang) parameter types are almost perfect but due to limitations in dbghelp the library cannot accurately show const and volatile qualifiers or rvalue references (these appear as pointers).

A couple features I'd like to add in the future:

• Tracing other thread's stacks

License

This library is under the MIT license.

Cpptrace uses libdwarf on linux, macos, and mingw/cygwin unless configured to use something else. If this library is statically linked with libdwarf then the library's binary will itself be LGPL.