Cpptrace

Cpptrace is a lightweight 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.

Some day C++23's <stacktrace> will be ubiquitous. And maybe one day the msvc implementation will be acceptable.

This library is in beta, if you run into any problems please open an issue!

Table of Contents

• 30-Second Overview
  • CMake FetchContent Usage
• In-Depth Documentation
  • API
  • Notable Library Configurations
  • Notes About the Library and Future Work
  • Usage
    • CMake FetchContent
    • System-Wide Installation
    • Local User Installation
    • Package Managers
    • Platform Logistics
    • Static Linking
  • Library Internals
    • Summary of Library Configurations
  • Testing Methodology
• License

30-Second Overview

Generating traces is as easy as calling cpptrace::print_trace:

#include <cpptrace/cpptrace.hpp>

void trace() {
    cpptrace::print_trace();
}

// ...

CMake FetchContent Usage

include(FetchContent)
FetchContent_Declare(
  cpptrace
  GIT_REPOSITORY https://github.com/jeremy-rifkin/cpptrace.git
  GIT_TAG        v0.1.1 # <HASH or TAG>
)
FetchContent_MakeAvailable(cpptrace)
target_link_libraries(your_target cpptrace)

On windows and macos some extra work is required, see below.

In-Depth Documentation

API

cpptrace::print_trace() can be used to print a stacktrace at the current call site, cpptrace::generate_trace() can be used to get raw frame information for custom use.

Note: Debug info (-g//Z7//Zi//DEBUG) is generally required for good trace information.

Note: Currently on Mac .dSYM files are required, which can be generated with dsymutil yourbinary. A cmake snippet for generating these is included above.

namespace cpptrace {
    struct stacktrace_frame {
        uintptr_t address;
        std::uint_least32_t line;
        std::uint_least32_t col;
        std::string filename;
        std::string symbol;
    };
    std::vector<stacktrace_frame> generate_trace(std::uint32_t skip = 0);
    void print_trace(std::uint32_t skip = 0);
}

Notable Library Configurations

• CPPTRACE_STATIC=On/Off: Create cpptrace as a static library.
• CPPTRACE_HARD_MAX_FRAMES=<number>: Some back-ends write to a fixed-size buffer. This is the size of that buffer. Default is 100.

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 fix in the future:

• On MacOS .dSYM files are required
• 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).
• On Windows unwinding with CaptureStackBackTrace (msvc/clang) can sometimes produce program counters that are after the call instruction. Execinfo suffers from the same problem, but libgcc's _Unwind provides a means to detect this. I would like to find a solution on windows so stack traces are more accurate.

Usage

CMake FetchContent

With CMake FetchContent:

include(FetchContent)
FetchContent_Declare(
  cpptrace
  GIT_REPOSITORY https://github.com/jeremy-rifkin/cpptrace.git
  GIT_TAG        v0.1.1 # <HASH or TAG>
)
FetchContent_MakeAvailable(cpptrace)
target_link_libraries(your_target 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 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 v0.1.1
mkdir cpptrace/build
cd cpptrace/build
cmake .. -DCMAKE_BUILD_TYPE=Release -DBUILD_SHARED_LIBS=On
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.

System-wide install on windows

git clone https://github.com/jeremy-rifkin/cpptrace.git
git checkout v0.1.1
mkdir cpptrace/build
cd cpptrace/build
cmake .. -DCMAKE_BUILD_TYPE=Release
msbuild cpptrace.sln
msbuild INSTALL.vcxproj

Note: You'll need to run as an administrator in a developer powershell, or use vcvarsall.bat distributed with visual studio to get the correct environment variables set.

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 v0.1.1
mkdir cpptrace/build
cd cpptrace/build
cmake .. -DCMAKE_BUILD_TYPE=Release -DBUILD_SHARED_LIBS=On -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

Package Managers

Coming soon

Platform Logistics

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

# 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>
    $<TARGET_FILE_DIR:your_target>
  )
endif()

# Create a .dSYM file on macos. Currently required, but hopefully not for long
if(APPLE)
  add_custom_command(
    TARGET your_target
    POST_BUILD
    COMMAND dsymutil $<TARGET_FILE:your_target>
  )
endif()

Static Linking

To static link the library set -DCPPTRACE_STATIC=On.

Library Internals

Cpptrace supports a number of back-ends and middle-ends to produce stack traces. Stack traces are produced in roughly three steps: Unwinding, symbol resolution, and demangling. Cpptrace by default on linux / macos will generate traces with _Unwind_Backtrace, libdwarf, and __cxa_demangle. On windows traces are generated by default with CaptureStackBackTrace and dbghelp.h (no demangling is needed with dbghelp). Under mingw libdwarf and dbghelp.h are used, along with __cxa_demangle. Support for these is the main focus of cpptrace and they should work well. If you want to use a different back-end such as addr2line, however, you can configure the library to do so.

Unwinding

Library	CMake config	Platforms	Info
libgcc unwind	CPPTRACE_UNWIND_WITH_UNWIND	linux, macos, mingw	Frames are captured with libgcc's _Unwind_Backtrace, which currently produces the most accurate stack traces on gcc/clang/mingw. Libgcc is often linked by default, and llvm has something equivalent.
execinfo.h	CPPTRACE_UNWIND_WITH_EXECINFO	linux, macos	Frames are captured with execinfo.h's backtrace, part of libc on linux/unix systems.
winapi	CPPTRACE_UNWIND_WITH_WINAPI	windows, mingw	Frames are captured with CaptureStackBackTrace.
N/A	CPPTRACE_UNWIND_WITH_NOTHING	all	Unwinding is not done, stack traces will be empty.

These back-ends require a fixed buffer has to be created to read addresses into while unwinding. By default the buffer can hold addresses for 100 frames (beyond the skip frames). This is configurable with CPPTRACE_HARD_MAX_FRAMES.

Symbol resolution

Library	CMake config	Platforms	Info
libdwarf	CPPTRACE_GET_SYMBOLS_WITH_LIBDWARF	linux, macos, mingw	Libdwarf is the preferred method for symbol resolution for cpptrace, and it's bundled in this repository for ease of use.
dbghelp	CPPTRACE_GET_SYMBOLS_WITH_DBGHELP	windows	Dbghelp.h is the preferred method for symbol resolution on windows under msvc/clang and is supported on all windows machines.
libbacktrace	CPPTRACE_GET_SYMBOLS_WITH_LIBBACKTRACE	linux, macos*, mingw*	Libbacktrace is already installed on most systems or available through the compiler directly. For clang you must specify the absolute path to backtrace.h using CPPTRACE_BACKTRACE_PATH.
addr2line	CPPTRACE_GET_SYMBOLS_WITH_ADDR2LINE	linux, macos, mingw	Symbols are resolved by invoking addr2line (or atos on mac) via fork() (on linux/unix, and popen under mingw).
libdl	CPPTRACE_GET_SYMBOLS_WITH_LIBDL	linux, macos	Libdl uses dynamic export information. Compiling with -rdynamic is needed for symbol information to be retrievable. Line numbers won't be retrievable.
N/A	CPPTRACE_GET_SYMBOLS_WITH_NOTHING	all	No attempt is made to resolve symbols.

*: Requires installation

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.

Library	CMake config	Platforms	Info
cxxabi.h	CPPTRACE_DEMANGLE_WITH_CXXABI	Linux, macos, mingw	Should be available everywhere other than msvc.
N/A	CPPTRACE_DEMANGLE_WITH_NOTHING	all	Don't attempt to do anything beyond what the symbol resolution back-end does.

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_EXECINFO=On/Off
• CPPTRACE_UNWIND_WITH_WINAPI=On/Off
• CPPTRACE_UNWIND_WITH_NOTHING=On/Off
• CPPTRACE_DEMANGLE_WITH_CXXABI=On/Off
• CPPTRACE_DEMANGLE_WITH_NOTHING=On/Off

Back-end configuration:

• CPPTRACE_STATIC=On/Off: Create cpptrace as a static library.
• 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 100.
• 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.

Testing:

• CPPTRACE_BUILD_TEST Build a small test program
• CPPTRACE_BUILD_DEMO Build a small demo 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.

License

This library is under the MIT license.

Libdwarf is bundled as part of this library so the code in bundled/libdwarf is LGPL. If this library is statically linked with libdwarf then the library's binary will itself be LGPL.