Outcome

master branch	develop branch

CTest dashboard: https://my.cdash.org/index.php?project=Boost.Outcome

All tests passing source tarballs: https://github.com/ned14/outcome/releases

Documentation: https://ned14.github.io/outcome/

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Presentation

Outcome is a lightweight C++14 library designed to handle and report function failures efficiently. It provides types outcome<T> and result<T> as an alternative or complement to exception handling, enabling explicit and predictable control of error conditions.

Use cases include:

• Environments where C++ exceptions are not suitable due to performance or policy.
• Systems requiring static control flow analysis for safety and correctness.
• Software architectures that propagate errors across threads without exceptions.
• Codebases compiled with -fno-exceptions or legacy systems without exception safety design.

Repository: https://github.com/thomgit9/outcome
Default branch: develop
License: Apache 2.0 / Boost Software License 1.0 dual license
Visibility: public

Maintainers:

• ned14 (primary author and maintainer)

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Installation

Outcome can be used either as a regular multi-header library or as a single header implementation.

Option 1 – Single header inclusion:

You may include the generated single header file directly in your project:

# Linux
wget https://github.com/ned14/outcome/raw/master/single-header/outcome.hpp

# BSD
fetch https://github.com/ned14/outcome/raw/master/single-header/outcome.hpp

# Using curl
curl -O -J -L https://github.com/ned14/outcome/raw/master/single-header/outcome.hpp

If debugging using Microsoft Visual Studio, consider including the debugger visualization file in your build for improved IDE integration.

Option 2 – CMake integration:

git clone https://github.com/thomgit9/outcome.git
cd outcome
cmake -B build
cmake --build build

CTest integration is available, reporting to CDash.

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Usage

Outcome provides robust result types for safer error handling.

Typical usage examples:

#include "outcome.hpp"
using namespace OUTCOME_V2_NAMESPACE;

result<int> divide(int a, int b)
{
  if(b == 0) return error_code(std::errc::invalid_argument);
  return a / b;
}

int main()
{
  auto r = divide(10, 2);
  if(r.has_value())
    std::cout << "Result: " << r.value() << std::endl;
  else
    std::cerr << "Error: " << r.error().message() << std::endl;
}

Outcome integrates with modern C++ constructs, supports coroutines, and interoperates with Boost.System and Standard error handling.

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Main Classes and Functions

Name	File	Description	Inputs	Outputs
result<T>	include/outcome/result.hpp	Represents a value or an error condition.	T, ErrorCode	Value T or ErrorCode
outcome<T>	include/outcome/outcome.hpp	Extends result<T> to include exception and error storage.	T, ErrorCode, Exception	Value T or error/exception information
basic_result	include/outcome/basic_result.hpp	Low-level generic implementation of result<T>.	Template type parameters	Typed result wrapper
basic_outcome	include/outcome/basic_outcome.hpp	Customizable core of outcome<T>.	Template type parameters	Structured result including error/exception states
try<T>	include/outcome/try.hpp	Provides macro helpers for concise error propagation.	Expression or callable returning result<T>	Returns unwrapped success or propagates failure
status_bits()	abi-compliance/src/main.cpp	Returns ABI-locked internal status bitfields for outcome.	None	Internal status mask
value_storage_int()	abi-compliance/src/main.cpp	ABI-locked storage accessor for trivial value types.	value_storage_trivial<int, long>&	Returns identical object
value_storage_NonTrivialType()	abi-compliance/src/main.cpp	ABI-locked storage accessor for non-trivial types.	value_storage_nontrivial<NonTrivialType, int>&	Returns identical object

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Developer Verification

Commits and tags in this repository can be verified using the following PGP key:

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