Merge pull request #15 from Progmasoft/feature/catch3-runner

Replace Catch2's runner with the Catch3 runner

1 files changed, 1289 insertions, 0 deletions

diff --git a/src/Progmasoft/Runner/Process.cpp b/src/Progmasoft/Runner/Process.cpp
new file mode 100644
index 00000000..8ef02327
--- /dev/null
+++ b/src/Progmasoft/Runner/Process.cpp
@@ -0,0 +1,1289 @@
+// Copyright (c) 2026 Progmasoft.
+// SPDX-License-Identifier: MPL-2.0 WITH AdditionRef-Progmasoft-Exception-1.1
+#include <algorithm>
+#include <cstdio>
+#include <cstdlib>
+#include <cstring>
+#include <thread>
+
+#include "Process.hpp"
+
+#if defined(_WIN32)
+#    ifndef NOMINMAX
+#        define NOMINMAX
+#    endif
+#    ifndef WIN32_LEAN_AND_MEAN
+#        define WIN32_LEAN_AND_MEAN
+#    endif
+#    include <fcntl.h>
+#    include <io.h>
+#    include <share.h>
+#    include <sys/stat.h>
+#    include <windows.h>
+#else
+#    include <cerrno>
+#    include <csignal>
+#    include <fcntl.h>
+#    include <spawn.h>
+#    include <sys/types.h>
+#    include <sys/wait.h>
+#    include <unistd.h>
+#    if defined(__APPLE__)
+#        include <crt_externs.h>
+#        include <mach-o/dyld.h>
+#    endif
+#    if !defined(__APPLE__) && !(defined(__GLIBC__) && defined(_GNU_SOURCE))
+extern char **environ;
+#    endif
+#endif
+
+namespace Progmasoft::Catch3::Runner
+{
+    namespace
+    {
+#if defined(_WIN32)
+        HANDLE
+        AsHandle(std::intptr_t value) noexcept
+        {
+            return reinterpret_cast<HANDLE>(value);
+        }
+
+        std::intptr_t
+        FromHandle(HANDLE handle) noexcept
+        {
+            return reinterpret_cast<std::intptr_t>(handle);
+        }
+
+        std::wstring
+        Widen(std::string_view text)
+        {
+            if (text.empty())
+            {
+                return {};
+            }
+            const int size = MultiByteToWideChar(CP_UTF8,
+                                                 0,
+                                                 text.data(),
+                                                 static_cast<int>(text.size()),
+                                                 nullptr,
+                                                 0);
+            std::wstring wide(static_cast<std::size_t>(size), L'\0');
+            MultiByteToWideChar(CP_UTF8,
+                                0,
+                                text.data(),
+                                static_cast<int>(text.size()),
+                                wide.data(),
+                                size);
+            return wide;
+        }
+
+        std::string
+        Narrow(std::wstring_view text)
+        {
+            if (text.empty())
+            {
+                return {};
+            }
+            const int size = WideCharToMultiByte(CP_UTF8,
+                                                 0,
+                                                 text.data(),
+                                                 static_cast<int>(text.size()),
+                                                 nullptr,
+                                                 0,
+                                                 nullptr,
+                                                 nullptr);
+            std::string narrow(static_cast<std::size_t>(size), '\0');
+            WideCharToMultiByte(CP_UTF8,
+                                0,
+                                text.data(),
+                                static_cast<int>(text.size()),
+                                narrow.data(),
+                                size,
+                                nullptr,
+                                nullptr);
+            return narrow;
+        }
+
+        std::string
+        LastErrorMessage(const char *what)
+        {
+            const DWORD code = GetLastError();
+            wchar_t *buffer = nullptr;
+            const DWORD length = FormatMessageW(
+                FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM
+                    | FORMAT_MESSAGE_IGNORE_INSERTS,
+                nullptr,
+                code,
+                0,
+                reinterpret_cast<wchar_t *>(&buffer),
+                0,
+                nullptr);
+            std::string message
+                = length > 0 ? Narrow(std::wstring_view{ buffer, length })
+                             : std::string{};
+            if (buffer != nullptr)
+            {
+                LocalFree(buffer);
+            }
+            while (!message.empty()
+                   && (message.back() == '\n' || message.back() == '\r'
+                       || message.back() == ' ' || message.back() == '.'))
+            {
+                message.pop_back();
+            }
+            return std::string{ what } + ": " + message + " (error "
+                   + std::to_string(code) + ")";
+        }
+
+        /// Quotes one argument the way the Microsoft C runtime splits a
+        /// command line back into `argv`.
+        void
+        AppendQuotedArgument(std::wstring &commandLine,
+                             const std::wstring &argument)
+        {
+            const bool needsQuotes
+                = argument.empty()
+                  || argument.find_first_of(L" \t\n\v\"") != std::wstring::npos;
+            if (!needsQuotes)
+            {
+                commandLine += argument;
+                return;
+            }
+            commandLine.push_back(L'"');
+            std::size_t backslashes = 0;
+            for (const wchar_t character : argument)
+            {
+                if (character == L'\\')
+                {
+                    ++backslashes;
+                    continue;
+                }
+                if (character == L'"')
+                {
+                    commandLine.append(backslashes * 2 + 1, L'\\');
+                }
+                else
+                {
+                    commandLine.append(backslashes, L'\\');
+                }
+                backslashes = 0;
+                commandLine.push_back(character);
+            }
+            commandLine.append(backslashes * 2, L'\\');
+            commandLine.push_back(L'"');
+        }
+
+        std::wstring
+        EnvironmentBlock(
+            const std::vector<std::pair<std::string, std::string>> &additions)
+        {
+            std::vector<std::wstring> entries;
+            wchar_t *current = GetEnvironmentStringsW();
+            if (current != nullptr)
+            {
+                for (const wchar_t *entry = current; *entry != L'\0';
+                     entry += wcslen(entry) + 1)
+                {
+                    entries.emplace_back(entry);
+                }
+                FreeEnvironmentStringsW(current);
+            }
+            for (const auto &[name, value] : additions)
+            {
+                const std::wstring wideName = Widen(name);
+                std::erase_if(entries, [&](const std::wstring &entry) {
+                    // A leading '=' marks the hidden per-drive variables.
+                    const auto equals = entry.find(L'=', 1);
+                    return equals == wideName.size()
+                           && CompareStringOrdinal(
+                                  entry.data(),
+                                  static_cast<int>(equals),
+                                  wideName.data(),
+                                  static_cast<int>(wideName.size()),
+                                  TRUE)
+                                  == CSTR_EQUAL;
+                });
+                entries.push_back(wideName + L"=" + Widen(value));
+            }
+            std::wstring block;
+            for (const auto &entry : entries)
+            {
+                block += entry;
+                block.push_back(L'\0');
+            }
+            block.push_back(L'\0');
+            return block;
+        }
+#else
+        int
+        Descriptor(std::intptr_t value) noexcept
+        {
+            return static_cast<int>(value);
+        }
+
+        char **
+        CurrentEnvironment() noexcept
+        {
+#    if defined(__APPLE__)
+            return *_NSGetEnviron();
+#    else
+            return environ;
+#    endif
+        }
+
+        std::string
+        ErrnoMessage(const char *what, int error)
+        {
+            return std::string{ what } + ": " + std::strerror(error);
+        }
+
+        bool
+        MakePipe(int (&descriptors)[2])
+        {
+#    if defined(__linux__)
+            return pipe2(descriptors, O_CLOEXEC) == 0;
+#    else
+            // Only the scheduler thread starts processes, so no other
+            // thread can fork between creating the pipe and marking it.
+            if (pipe(descriptors) != 0)
+            {
+                return false;
+            }
+            fcntl(descriptors[0], F_SETFD, FD_CLOEXEC);
+            fcntl(descriptors[1], F_SETFD, FD_CLOEXEC);
+            return true;
+#    endif
+        }
+
+        const char *
+        SignalName(int signal) noexcept
+        {
+            switch (signal)
+            {
+                case SIGSEGV:
+                    return "SIGSEGV";
+                case SIGABRT:
+                    return "SIGABRT";
+                case SIGBUS:
+                    return "SIGBUS";
+                case SIGFPE:
+                    return "SIGFPE";
+                case SIGILL:
+                    return "SIGILL";
+                case SIGKILL:
+                    return "SIGKILL";
+                case SIGTERM:
+                    return "SIGTERM";
+                case SIGPIPE:
+                    return "SIGPIPE";
+                case SIGINT:
+                    return "SIGINT";
+                default:
+                    return nullptr;
+            }
+        }
+#endif
+
+#if defined(_WIN32)
+        const char *
+        ExceptionName(std::int64_t code) noexcept
+        {
+            switch (static_cast<DWORD>(code))
+            {
+                case 0xC0000005:
+                    return "access violation";
+                case 0xC00000FD:
+                    return "stack overflow";
+                case 0xC0000094:
+                    return "integer division by zero";
+                case 0xC000008E:
+                    return "floating-point division by zero";
+                case 0xC000001D:
+                    return "illegal instruction";
+                case 0xC0000409:
+                    return "stack buffer overrun or fast fail";
+                case 0xC0000374:
+                    return "heap corruption";
+                case 0x80000003:
+                    return "breakpoint";
+                case 0xE06D7363:
+                    return "unhandled C++ exception";
+                default:
+                    return nullptr;
+            }
+        }
+#endif
+    } // namespace
+
+    std::string
+    ExitStatus::Describe() const
+    {
+        switch (kind)
+        {
+            case Kind::kExited:
+                return "exit code " + std::to_string(code);
+            case Kind::kSignaled:
+            {
+                std::string text = "signal " + std::to_string(code);
+#if !defined(_WIN32)
+                if (const char *name = SignalName(static_cast<int>(code)))
+                {
+                    text += std::string{ " (" } + name + ")";
+                }
+#endif
+                return text;
+            }
+            case Kind::kException:
+            {
+                char buffer[32];
+                std::snprintf(buffer,
+                              sizeof(buffer),
+                              "0x%08llX",
+                              static_cast<unsigned long long>(code));
+                std::string text = std::string{ "exception " } + buffer;
+#if defined(_WIN32)
+                if (const char *name = ExceptionName(code))
+                {
+                    text += std::string{ " (" } + name + ")";
+                }
+#endif
+                return text;
+            }
+        }
+        return "unknown status";
+    }
+
+    PipeReader::PipeReader(PipeReader &&other) noexcept
+        : handle_{ other.handle_ }
+    {
+        other.handle_ = -1;
+    }
+
+    PipeReader &
+    PipeReader::operator=(PipeReader &&other) noexcept
+    {
+        if (this != &other)
+        {
+            Close();
+            handle_ = other.handle_;
+            other.handle_ = -1;
+        }
+        return *this;
+    }
+
+    PipeReader::~PipeReader()
+    {
+        Close();
+    }
+
+    bool
+    PipeReader::IsOpen() const noexcept
+    {
+        return handle_ != -1;
+    }
+
+    void
+    PipeReader::Close() noexcept
+    {
+        if (handle_ == -1)
+        {
+            return;
+        }
+#if defined(_WIN32)
+        CloseHandle(AsHandle(handle_));
+#else
+        close(Descriptor(handle_));
+#endif
+        handle_ = -1;
+    }
+
+    std::int64_t
+    PipeReader::Read(char *buffer, std::size_t size) noexcept
+    {
+        if (handle_ == -1)
+        {
+            return -1;
+        }
+#if defined(_WIN32)
+        DWORD read = 0;
+        const DWORD request
+            = size > 0x10000000 ? 0x10000000 : static_cast<DWORD>(size);
+        if (!::ReadFile(AsHandle(handle_), buffer, request, &read, nullptr))
+        {
+            const DWORD error = GetLastError();
+            return error == ERROR_BROKEN_PIPE || error == ERROR_NO_DATA ? 0
+                                                                        : -1;
+        }
+        return static_cast<std::int64_t>(read);
+#else
+        while (true)
+        {
+            const auto count = read(Descriptor(handle_), buffer, size);
+            if (count >= 0)
+            {
+                return static_cast<std::int64_t>(count);
+            }
+            if (errno != EINTR)
+            {
+                return -1;
+            }
+        }
+#endif
+    }
+
+    PipeWriter::PipeWriter(PipeWriter &&other) noexcept
+        : handle_{ other.handle_ }
+    {
+        other.handle_ = -1;
+    }
+
+    PipeWriter &
+    PipeWriter::operator=(PipeWriter &&other) noexcept
+    {
+        if (this != &other)
+        {
+            Close();
+            handle_ = other.handle_;
+            other.handle_ = -1;
+        }
+        return *this;
+    }
+
+    PipeWriter::~PipeWriter()
+    {
+        Close();
+    }
+
+    bool
+    PipeWriter::IsOpen() const noexcept
+    {
+        return handle_ != -1;
+    }
+
+    void
+    PipeWriter::Close() noexcept
+    {
+        if (handle_ == -1)
+        {
+            return;
+        }
+#if defined(_WIN32)
+        CloseHandle(AsHandle(handle_));
+#else
+        close(Descriptor(handle_));
+#endif
+        handle_ = -1;
+    }
+
+    Status
+    PipeWriter::Write(std::string_view data) noexcept
+    {
+        if (handle_ == -1)
+        {
+            return Error{ "the pipe is closed" };
+        }
+        while (!data.empty())
+        {
+#if defined(_WIN32)
+            DWORD written = 0;
+            const DWORD request = data.size() > 0x10000000
+                                      ? 0x10000000
+                                      : static_cast<DWORD>(data.size());
+            if (!::WriteFile(AsHandle(handle_),
+                             data.data(),
+                             request,
+                             &written,
+                             nullptr))
+            {
+                return Error{ "the other end of the pipe is gone" };
+            }
+            data.remove_prefix(written);
+#else
+            const auto count
+                = write(Descriptor(handle_), data.data(), data.size());
+            if (count < 0)
+            {
+                if (errno == EINTR)
+                {
+                    continue;
+                }
+                return Error{ ErrnoMessage("cannot write to the pipe", errno) };
+            }
+            data.remove_prefix(static_cast<std::size_t>(count));
+#endif
+        }
+        return Status::Ok();
+    }
+
+    ChildProcess::~ChildProcess()
+    {
+        if (!exit_)
+        {
+            Kill();
+            static_cast<void>(Wait());
+        }
+#if defined(_WIN32)
+        if (process_ != -1)
+        {
+            CloseHandle(AsHandle(process_));
+        }
+        if (group_ != -1)
+        {
+            CloseHandle(AsHandle(group_));
+        }
+#endif
+    }
+
+#if defined(_WIN32)
+    Expected<std::unique_ptr<ChildProcess>>
+    ChildProcess::Start(const ChildOptions &options)
+    {
+        if (options.arguments.empty())
+        {
+            return Error{ "no program to start" };
+        }
+        SECURITY_ATTRIBUTES inheritable{};
+        inheritable.nLength = sizeof(inheritable);
+        inheritable.bInheritHandle = TRUE;
+
+        HANDLE pipes[3][2] = {};
+        for (auto &pipe : pipes)
+        {
+            if (!CreatePipe(&pipe[0], &pipe[1], &inheritable, 0))
+            {
+                const std::string message
+                    = LastErrorMessage("cannot create a pipe");
+                for (auto &created : pipes)
+                {
+                    for (HANDLE handle : created)
+                    {
+                        if (handle != nullptr)
+                        {
+                            CloseHandle(handle);
+                        }
+                    }
+                }
+                return Error{ message };
+            }
+        }
+        // The child gets the read end of its input and the write ends of its
+        // output; the ends this process keeps are not inheritable.
+        HANDLE childInput = pipes[0][0];
+        HANDLE parentInput = pipes[0][1];
+        HANDLE parentOutput = pipes[1][0];
+        HANDLE childOutput = pipes[1][1];
+        HANDLE parentErrors = pipes[2][0];
+        HANDLE childErrors = pipes[2][1];
+        SetHandleInformation(parentInput, HANDLE_FLAG_INHERIT, 0);
+        SetHandleInformation(parentOutput, HANDLE_FLAG_INHERIT, 0);
+        SetHandleInformation(parentErrors, HANDLE_FLAG_INHERIT, 0);
+
+        auto closeChildEnds = [&] {
+            CloseHandle(childInput);
+            CloseHandle(childOutput);
+            CloseHandle(childErrors);
+        };
+
+        std::unique_ptr<ChildProcess> child{ new ChildProcess{} };
+        child->input_ = PipeWriter{ FromHandle(parentInput) };
+        child->output_ = PipeReader{ FromHandle(parentOutput) };
+        child->errors_ = PipeReader{ FromHandle(parentErrors) };
+
+        // Only these three handles are inherited, so a worker never holds
+        // the pipes of another one open.
+        HANDLE inherited[3] = { childInput, childOutput, childErrors };
+        SIZE_T attributeSize = 0;
+        InitializeProcThreadAttributeList(nullptr, 1, 0, &attributeSize);
+        std::vector<unsigned char> attributeStorage(attributeSize);
+        auto *attributes = reinterpret_cast<LPPROC_THREAD_ATTRIBUTE_LIST>(
+            attributeStorage.data());
+        if (!InitializeProcThreadAttributeList(attributes, 1, 0, &attributeSize)
+            || !UpdateProcThreadAttribute(attributes,
+                                          0,
+                                          PROC_THREAD_ATTRIBUTE_HANDLE_LIST,
+                                          inherited,
+                                          sizeof(inherited),
+                                          nullptr,
+                                          nullptr))
+        {
+            const std::string message
+                = LastErrorMessage("cannot prepare the process attributes");
+            closeChildEnds();
+            return Error{ message };
+        }
+
+        STARTUPINFOEXW startup{};
+        startup.StartupInfo.cb = sizeof(startup);
+        startup.StartupInfo.dwFlags = STARTF_USESTDHANDLES;
+        startup.StartupInfo.hStdInput = childInput;
+        startup.StartupInfo.hStdOutput = childOutput;
+        startup.StartupInfo.hStdError = childErrors;
+        startup.lpAttributeList = attributes;
+
+        std::wstring program = Widen(options.arguments.front());
+        std::wstring commandLine;
+        for (std::size_t index = 0; index < options.arguments.size(); ++index)
+        {
+            if (index > 0)
+            {
+                commandLine.push_back(L' ');
+            }
+            AppendQuotedArgument(commandLine, Widen(options.arguments[index]));
+        }
+        std::wstring environment = EnvironmentBlock(options.environment);
+        const std::wstring directory = options.workingDirectory.wstring();
+
+        PROCESS_INFORMATION information{};
+        const BOOL created
+            = CreateProcessW(options.searchPath ? nullptr : program.c_str(),
+                             commandLine.data(),
+                             nullptr,
+                             nullptr,
+                             TRUE,
+                             CREATE_UNICODE_ENVIRONMENT | CREATE_SUSPENDED
+                                 | EXTENDED_STARTUPINFO_PRESENT,
+                             environment.data(),
+                             directory.empty() ? nullptr : directory.c_str(),
+                             &startup.StartupInfo,
+                             &information);
+        DeleteProcThreadAttributeList(attributes);
+        if (!created)
+        {
+            const std::string message = LastErrorMessage(
+                ("cannot start '" + options.arguments.front() + "'").c_str());
+            closeChildEnds();
+            return Error{ message };
+        }
+        closeChildEnds();
+
+        // A job ends the whole tree at once, and its limit keeps a crash from
+        // waiting on the error-reporting dialog.
+        HANDLE job = CreateJobObjectW(nullptr, nullptr);
+        if (job != nullptr)
+        {
+            JOBOBJECT_EXTENDED_LIMIT_INFORMATION limits{};
+            limits.BasicLimitInformation.LimitFlags
+                = JOB_OBJECT_LIMIT_KILL_ON_JOB_CLOSE
+                  | JOB_OBJECT_LIMIT_DIE_ON_UNHANDLED_EXCEPTION;
+            SetInformationJobObject(job,
+                                    JobObjectExtendedLimitInformation,
+                                    &limits,
+                                    sizeof(limits));
+            if (!AssignProcessToJobObject(job, information.hProcess))
+            {
+                CloseHandle(job);
+                job = nullptr;
+            }
+        }
+        ResumeThread(information.hThread);
+        CloseHandle(information.hThread);
+
+        child->id_ = static_cast<std::int64_t>(information.dwProcessId);
+        child->process_ = FromHandle(information.hProcess);
+        child->group_ = job == nullptr ? -1 : FromHandle(job);
+        return child;
+    }
+
+    void
+    ChildProcess::Kill() noexcept
+    {
+        if (exit_)
+        {
+            return;
+        }
+        if (group_ != -1)
+        {
+            TerminateJobObject(AsHandle(group_), 0xC000013A);
+        }
+        else if (process_ != -1)
+        {
+            TerminateProcess(AsHandle(process_), 0xC000013A);
+        }
+    }
+
+    ExitStatus
+    ChildProcess::Wait() noexcept
+    {
+        if (exit_)
+        {
+            return *exit_;
+        }
+        ExitStatus status;
+        if (process_ != -1)
+        {
+            WaitForSingleObject(AsHandle(process_), INFINITE);
+            DWORD code = 0;
+            GetExitCodeProcess(AsHandle(process_), &code);
+            status.code = static_cast<std::int64_t>(code);
+            // NTSTATUS error codes have both top bits set.
+            status.kind
+                = (code & 0xC0000000U) == 0xC0000000U || code == 0x80000003U
+                      ? ExitStatus::Kind::kException
+                      : ExitStatus::Kind::kExited;
+            if (status.kind == ExitStatus::Kind::kExited && code > 0x7FFFFFFFU)
+            {
+                status.code = static_cast<std::int32_t>(code);
+            }
+        }
+        exit_ = status;
+        return status;
+    }
+
+    std::optional<ExitStatus>
+    ChildProcess::WaitFor(std::chrono::milliseconds timeout) noexcept
+    {
+        if (exit_ || process_ == -1)
+        {
+            return Wait();
+        }
+        const auto waited = WaitForSingleObject(
+            AsHandle(process_),
+            static_cast<DWORD>(std::max<long long>(0, timeout.count())));
+        if (waited == WAIT_TIMEOUT)
+        {
+            return std::nullopt;
+        }
+        return Wait();
+    }
+
+    Expected<WorkerStreams>
+    TakeStandardStreams()
+    {
+        HANDLE process = GetCurrentProcess();
+        HANDLE input = nullptr;
+        HANDLE output = nullptr;
+        if (!DuplicateHandle(process,
+                             GetStdHandle(STD_INPUT_HANDLE),
+                             process,
+                             &input,
+                             0,
+                             FALSE,
+                             DUPLICATE_SAME_ACCESS)
+            || !DuplicateHandle(process,
+                                GetStdHandle(STD_OUTPUT_HANDLE),
+                                process,
+                                &output,
+                                0,
+                                FALSE,
+                                DUPLICATE_SAME_ACCESS))
+        {
+            return Error{ LastErrorMessage(
+                "cannot take the standard streams") };
+        }
+        std::fflush(stdout);
+        int nullDescriptor = -1;
+        _sopen_s(&nullDescriptor,
+                 "NUL",
+                 _O_RDONLY | _O_BINARY,
+                 _SH_DENYNO,
+                 _S_IREAD);
+        if (nullDescriptor >= 0)
+        {
+            _dup2(nullDescriptor, 0);
+            _close(nullDescriptor);
+        }
+        _dup2(2, 1);
+        // The runner writes what the worker prints through its own text-mode
+        // streams; translating line ends here as well would double them.
+        _setmode(1, _O_BINARY);
+        _setmode(2, _O_BINARY);
+        SetStdHandle(STD_INPUT_HANDLE,
+                     reinterpret_cast<HANDLE>(_get_osfhandle(0)));
+        SetStdHandle(STD_OUTPUT_HANDLE, GetStdHandle(STD_ERROR_HANDLE));
+        WorkerStreams streams;
+        streams.commands = PipeReader{ FromHandle(input) };
+        streams.events = PipeWriter{ FromHandle(output) };
+        return streams;
+    }
+
+    std::filesystem::path
+    CurrentExecutable(const char *argumentZero)
+    {
+        std::wstring buffer(MAX_PATH, L'\0');
+        while (true)
+        {
+            const DWORD length
+                = GetModuleFileNameW(nullptr,
+                                     buffer.data(),
+                                     static_cast<DWORD>(buffer.size()));
+            if (length == 0)
+            {
+                return argumentZero == nullptr
+                           ? std::filesystem::path{}
+                           : std::filesystem::path{ argumentZero };
+            }
+            if (length < buffer.size())
+            {
+                buffer.resize(length);
+                return std::filesystem::path{ buffer };
+            }
+            buffer.resize(buffer.size() * 2);
+        }
+    }
+
+    std::string
+    ReadEnvironment(const char *name)
+    {
+        const std::wstring wideName = Widen(name);
+        const DWORD size
+            = GetEnvironmentVariableW(wideName.c_str(), nullptr, 0);
+        if (size == 0)
+        {
+            return {};
+        }
+        std::wstring value(size, L'\0');
+        const DWORD length
+            = GetEnvironmentVariableW(wideName.c_str(), value.data(), size);
+        value.resize(length);
+        return Narrow(value);
+    }
+
+    bool
+    HasEnvironment(const char *name)
+    {
+        const std::wstring wideName = Widen(name);
+        return GetEnvironmentVariableW(wideName.c_str(), nullptr, 0) > 0
+               || GetLastError() != ERROR_ENVVAR_NOT_FOUND;
+    }
+
+    bool
+    IsStandardOutputTerminal() noexcept
+    {
+        DWORD mode = 0;
+        return GetConsoleMode(GetStdHandle(STD_OUTPUT_HANDLE), &mode) != 0;
+    }
+
+    bool
+    EnableTerminalColours() noexcept
+    {
+        HANDLE output = GetStdHandle(STD_OUTPUT_HANDLE);
+        DWORD mode = 0;
+        if (!GetConsoleMode(output, &mode))
+        {
+            return false;
+        }
+        return SetConsoleMode(output, mode | ENABLE_VIRTUAL_TERMINAL_PROCESSING)
+               != 0;
+    }
+
+    void
+    QuietCrashReporting() noexcept
+    {
+        SetErrorMode(SEM_FAILCRITICALERRORS | SEM_NOGPFAULTERRORBOX
+                     | SEM_NOOPENFILEERRORBOX);
+        _set_abort_behavior(0, _WRITE_ABORT_MSG | _CALL_REPORTFAULT);
+    }
+
+    std::int64_t
+    CurrentProcessId() noexcept
+    {
+        return static_cast<std::int64_t>(GetCurrentProcessId());
+    }
+
+    void
+    WriteStandardError(std::string_view text) noexcept
+    {
+        while (!text.empty())
+        {
+            const unsigned chunk = static_cast<unsigned>(
+                std::min<std::size_t>(text.size(), 1U << 20U));
+            const int written = _write(2, text.data(), chunk);
+            if (written <= 0)
+            {
+                return;
+            }
+            text.remove_prefix(static_cast<std::size_t>(written));
+        }
+    }
+#else
+    Expected<std::unique_ptr<ChildProcess>>
+    ChildProcess::Start(const ChildOptions &options)
+    {
+        if (options.arguments.empty())
+        {
+            return Error{ "no program to start" };
+        }
+        int input[2] = { -1, -1 };
+        int output[2] = { -1, -1 };
+        int errors[2] = { -1, -1 };
+        auto closeAll = [&] {
+            for (int *pipe : { input, output, errors })
+            {
+                for (int index = 0; index < 2; ++index)
+                {
+                    if (pipe[index] != -1)
+                    {
+                        close(pipe[index]);
+                        pipe[index] = -1;
+                    }
+                }
+            }
+        };
+        if (!MakePipe(input) || !MakePipe(output) || !MakePipe(errors))
+        {
+            const int error = errno;
+            closeAll();
+            return Error{ ErrnoMessage("cannot create a pipe", error) };
+        }
+
+        posix_spawn_file_actions_t actions;
+        posix_spawn_file_actions_init(&actions);
+        posix_spawn_file_actions_adddup2(&actions, input[0], 0);
+        posix_spawn_file_actions_adddup2(&actions, output[1], 1);
+        posix_spawn_file_actions_adddup2(&actions, errors[1], 2);
+
+        posix_spawnattr_t attributes;
+        posix_spawnattr_init(&attributes);
+        sigset_t defaults;
+        sigemptyset(&defaults);
+        // The runner ignores SIGPIPE; a test must see the default.
+        sigaddset(&defaults, SIGPIPE);
+        posix_spawnattr_setsigdefault(&attributes, &defaults);
+        sigset_t mask;
+        sigemptyset(&mask);
+        posix_spawnattr_setsigmask(&attributes, &mask);
+        posix_spawnattr_setpgroup(&attributes, 0);
+        posix_spawnattr_setflags(&attributes,
+                                 static_cast<short>(POSIX_SPAWN_SETPGROUP
+                                                    | POSIX_SPAWN_SETSIGDEF
+                                                    | POSIX_SPAWN_SETSIGMASK));
+
+        std::vector<std::string> environmentStorage;
+        for (char **entry = CurrentEnvironment();
+             entry != nullptr && *entry != nullptr;
+             ++entry)
+        {
+            environmentStorage.emplace_back(*entry);
+        }
+        for (const auto &[name, value] : options.environment)
+        {
+            std::erase_if(environmentStorage, [&](const std::string &entry) {
+                return entry.size() > name.size()
+                       && entry.compare(0, name.size(), name) == 0
+                       && entry[name.size()] == '=';
+            });
+            environmentStorage.push_back(name + "=" + value);
+        }
+        std::vector<char *> environment;
+        environment.reserve(environmentStorage.size() + 1);
+        for (auto &entry : env