/**********************************************************************

 *

 * Project:  CPL - Common Portability Library

 * Purpose:  Implement CPLSystem().

 * Author:   Even Rouault, <even dot rouault at spatialys.com>

 *

 **********************************************************************

 * Copyright (c) 2012-2013, Even Rouault <even dot rouault at spatialys.com>

 *

 * SPDX-License-Identifier: MIT

 ****************************************************************************/

#include "cpl_port.h"

#include "cpl_spawn.h"

#include <cstring>

#include "cpl_config.h"

#include "cpl_conv.h"

#include "cpl_error.h"

#include "cpl_multiproc.h"

#include "cpl_string.h"

#if defined(_WIN32)

#include <windows.h>

#else

#include <cassert>

#include <cerrno>

#include <csignal>

#include <cstdio>

#include <cstdlib>

#include <sys/types.h>

#include <sys/wait.h>

#include <unistd.h>

#ifdef HAVE_POSIX_SPAWNP

#include <spawn.h>

#ifdef __APPLE__

#include <TargetConditionals.h>

#endif

#if defined(__APPLE__) && (!defined(TARGET_OS_IPHONE) || TARGET_OS_IPHONE == 0)

#include <crt_externs.h>

#define environ (*_NSGetEnviron())

#else

#if defined(__FreeBSD__)

extern __attribute__((__weak__)) char **environ;

#else

extern char **environ;

#endif

#endif

#endif

#endif

constexpr int PIPE_BUFFER_SIZE = 4096;

constexpr int IN_FOR_PARENT = 0;

constexpr int OUT_FOR_PARENT = 1;

static void FillFileFromPipe(CPL_FILE_HANDLE pipe_fd, VSILFILE *fout);

/************************************************************************/

/*                        FillPipeFromFile()                            */

/************************************************************************/

static void FillPipeFromFile(VSILFILE *fin, CPL_FILE_HANDLE pipe_fd)

{

    char buf[PIPE_BUFFER_SIZE] = {};

    while (true)

    {

        const int nRead =

            static_cast<int>(VSIFReadL(buf, 1, PIPE_BUFFER_SIZE, fin));

        if (nRead <= 0)

            break;

        if (!CPLPipeWrite(pipe_fd, buf, nRead))

            break;

    }

}

/************************************************************************/

/*                            CPLSpawn()                                */

/************************************************************************/

/**

 * Runs an executable in another process.

 *

 * This function runs an executable, wait for it to finish and returns

 * its exit code.

 *

 * It is implemented as CreateProcess() on Windows platforms, and fork()/exec()

 * on other platforms.

 *

 * @param papszArgv argument list of the executable to run. papszArgv[0] is the

 *                  name of the executable

 * @param fin File handle for input data to feed to the standard input of the

 *            sub-process. May be NULL.

 * @param fout File handle for output data to extract from the standard output

 *            of the sub-process. May be NULL.

 * @param bDisplayErr Set to TRUE to emit the content of the standard error

 *                    stream of the sub-process with CPLError().

 *

 * @return the exit code of the spawned process, or -1 in case of error.

 *

 * @since GDAL 1.10.0

 */

int CPLSpawn(const char *const papszArgv[], VSILFILE *fin, VSILFILE *fout,

             int bDisplayErr)

{

    CPLSpawnedProcess *sp =

        CPLSpawnAsync(nullptr, papszArgv, TRUE, TRUE, TRUE, nullptr);

    if (sp == nullptr)

        return -1;

    CPL_FILE_HANDLE in_child = CPLSpawnAsyncGetOutputFileHandle(sp);

    if (fin != nullptr)

        FillPipeFromFile(fin, in_child);

    CPLSpawnAsyncCloseOutputFileHandle(sp);

    CPL_FILE_HANDLE out_child = CPLSpawnAsyncGetInputFileHandle(sp);

    if (fout != nullptr)

        FillFileFromPipe(out_child, fout);

    CPLSpawnAsyncCloseInputFileHandle(sp);

    CPL_FILE_HANDLE err_child = CPLSpawnAsyncGetErrorFileHandle(sp);

    CPLString osName;

    osName.Printf("/vsimem/child_stderr_" CPL_FRMT_GIB, CPLGetPID());

    VSILFILE *ferr = VSIFOpenL(osName.c_str(), "w");

    FillFileFromPipe(err_child, ferr);

    CPLSpawnAsyncCloseErrorFileHandle(sp);

    CPL_IGNORE_RET_VAL(VSIFCloseL(ferr));

    vsi_l_offset nDataLength = 0;

    GByte *pData = VSIGetMemFileBuffer(osName.c_str(), &nDataLength, TRUE);

    if (nDataLength > 0)

        pData[nDataLength - 1] = '\0';

    if (pData &&

        strstr(const_cast<const char *>(reinterpret_cast<char *>(pData)),

               "An error occurred while forking process") != nullptr)

        bDisplayErr = TRUE;

    if (pData && bDisplayErr)

        CPLError(CE_Failure, CPLE_AppDefined, "[%s error] %s", papszArgv[0],

                 pData);

    CPLFree(pData);

    return CPLSpawnAsyncFinish(sp, TRUE, FALSE);

}

#if defined(_WIN32)

/************************************************************************/

/*                          CPLPipeRead()                               */

/************************************************************************/

int CPLPipeRead(CPL_FILE_HANDLE fin, void *data, int length)

{

    GByte *pabyData = static_cast<GByte *>(data);

    int nRemain = length;

    while (nRemain > 0)

    {

        DWORD nRead = 0;

        if (!ReadFile(fin, pabyData, nRemain, &nRead, nullptr))

            return FALSE;

        pabyData += nRead;

        nRemain -= nRead;

    }

    return TRUE;

}

/************************************************************************/

/*                         CPLPipeWrite()                               */

/************************************************************************/

int CPLPipeWrite(CPL_FILE_HANDLE fout, const void *data, int length)

{

    const GByte *pabyData = static_cast<const GByte *>(data);

    int nRemain = length;

    while (nRemain > 0)

    {

        DWORD nWritten = 0;

        if (!WriteFile(fout, pabyData, nRemain, &nWritten, nullptr))

            return FALSE;

        pabyData += nWritten;

        nRemain -= nWritten;

    }

    return TRUE;

}

/************************************************************************/

/*                        FillFileFromPipe()                            */

/************************************************************************/

static void FillFileFromPipe(CPL_FILE_HANDLE pipe_fd, VSILFILE *fout)

{

    char buf[PIPE_BUFFER_SIZE] = {};

    while (true)

    {

        DWORD nRead = 0;

        if (!ReadFile(pipe_fd, buf, PIPE_BUFFER_SIZE, &nRead, nullptr))

            break;

        if (nRead <= 0)

            break;

        const int nWritten = static_cast<int>(VSIFWriteL(buf, 1, nRead, fout));

        if (nWritten < static_cast<int>(nRead))

            break;

    }

}

struct _CPLSpawnedProcess

{

    HANDLE hProcess;

    DWORD nProcessId;

    HANDLE hThread;

    CPL_FILE_HANDLE fin;

    CPL_FILE_HANDLE fout;

    CPL_FILE_HANDLE ferr;

};

/************************************************************************/

/*                            CPLSpawnAsync()                           */

/************************************************************************/

CPLSpawnedProcess *

CPLSpawnAsync(CPL_UNUSED int (*pfnMain)(CPL_FILE_HANDLE, CPL_FILE_HANDLE),

              const char *const papszArgv[], int bCreateInputPipe,

              int bCreateOutputPipe, int bCreateErrorPipe,

              char ** /* papszOptions */)

{

    if (papszArgv == nullptr)

    {

        CPLError(CE_Failure, CPLE_AppDefined,

                 "On Windows, papszArgv argument must not be NULL");

        return nullptr;

    }

    // TODO(schwehr): Consider initializing saAttr.

    SECURITY_ATTRIBUTES saAttr;

    saAttr.nLength = sizeof(SECURITY_ATTRIBUTES);

    saAttr.bInheritHandle = TRUE;

    saAttr.lpSecurityDescriptor = nullptr;

    // TODO(schwehr): Move these to where they are used after gotos are removed.

    HANDLE pipe_out[2] = {nullptr, nullptr};

    HANDLE pipe_err[2] = {nullptr, nullptr};

    CPLString osCommandLine;

    HANDLE pipe_in[2] = {nullptr, nullptr};

    if (bCreateInputPipe)

    {

        if (!CreatePipe(&pipe_in[IN_FOR_PARENT], &pipe_in[OUT_FOR_PARENT],

                        &saAttr, 0))

            goto err_pipe;

        // The child must not inherit from the write side of the pipe_in.

        if (!SetHandleInformation(pipe_in[OUT_FOR_PARENT], HANDLE_FLAG_INHERIT,

                                  0))

            goto err_pipe;

    }

    if (bCreateOutputPipe)

    {

        if (!CreatePipe(&pipe_out[IN_FOR_PARENT], &pipe_out[OUT_FOR_PARENT],

                        &saAttr, 0))

            goto err_pipe;

        // The child must not inherit from the read side of the pipe_out.

        if (!SetHandleInformation(pipe_out[IN_FOR_PARENT], HANDLE_FLAG_INHERIT,

                                  0))

            goto err_pipe;

    }

    if (bCreateErrorPipe)

    {

        if (!CreatePipe(&pipe_err[IN_FOR_PARENT], &pipe_err[OUT_FOR_PARENT],

                        &saAttr, 0))

            goto err_pipe;

        // The child must not inherit from the read side of the pipe_err.

        if (!SetHandleInformation(pipe_err[IN_FOR_PARENT], HANDLE_FLAG_INHERIT,

                                  0))

            goto err_pipe;

    }

    // TODO(schwehr): Consider initializing piProcInfo.

    PROCESS_INFORMATION piProcInfo;

    memset(&piProcInfo, 0, sizeof(PROCESS_INFORMATION));

    STARTUPINFO siStartInfo;

    memset(&siStartInfo, 0, sizeof(STARTUPINFO));

    siStartInfo.cb = sizeof(STARTUPINFO);

    siStartInfo.hStdInput = bCreateInputPipe ? pipe_in[IN_FOR_PARENT]

                                             : GetStdHandle(STD_INPUT_HANDLE);

    siStartInfo.hStdOutput = bCreateOutputPipe

                                 ? pipe_out[OUT_FOR_PARENT]

                                 : GetStdHandle(STD_OUTPUT_HANDLE);

    siStartInfo.hStdError = bCreateErrorPipe ? pipe_err[OUT_FOR_PARENT]

                                             : GetStdHandle(STD_ERROR_HANDLE);

    siStartInfo.dwFlags |= STARTF_USESTDHANDLES;

    for (int i = 0; papszArgv[i] != nullptr; i++)

    {

        if (i > 0)

            osCommandLine += " ";

        // We need to quote arguments with spaces in them (if not already done).

        if (strchr(papszArgv[i], ' ') != nullptr && papszArgv[i][0] != '"')

        {

            osCommandLine += "\"";

            osCommandLine += papszArgv[i];

            osCommandLine += "\"";

        }

        else

        {

            osCommandLine += papszArgv[i];

        }

    }

    if (!CreateProcess(nullptr, const_cast<CHAR *>(osCommandLine.c_str()),

                       nullptr,  // Process security attributes

                       nullptr,  // Primary thread security attributes

                       TRUE,     // Handles are inherited

                       CREATE_NO_WINDOW |

                           NORMAL_PRIORITY_CLASS,  // Creation flags

                       nullptr,                    // Use parent's environment

                       nullptr,  // Use parent's current directory

                       &siStartInfo, &piProcInfo))

    {

        CPLError(CE_Failure, CPLE_AppDefined, "Could not create process %s",

                 osCommandLine.c_str());

        goto err;

    }

    // Close unused end of pipe.

    if (bCreateInputPipe)

        CloseHandle(pipe_in[IN_FOR_PARENT]);

    if (bCreateOutputPipe)

        CloseHandle(pipe_out[OUT_FOR_PARENT]);

    if (bCreateErrorPipe)

        CloseHandle(pipe_err[OUT_FOR_PARENT]);

    {

        CPLSpawnedProcess *p = static_cast<CPLSpawnedProcess *>(

            CPLMalloc(sizeof(CPLSpawnedProcess)));

        p->hProcess = piProcInfo.hProcess;

        p->nProcessId = piProcInfo.dwProcessId;

        p->hThread = piProcInfo.hThread;

        p->fin = pipe_out[IN_FOR_PARENT];

        p->fout = pipe_in[OUT_FOR_PARENT];

        p->ferr = pipe_err[IN_FOR_PARENT];

        return p;

    }

err_pipe:

    CPLError(CE_Failure, CPLE_AppDefined, "Could not create pipe");

err:

    for (int i = 0; i < 2; i++)

    {

        if (pipe_in[i] != nullptr)

            CloseHandle(pipe_in[i]);

        if (pipe_out[i] != nullptr)

            CloseHandle(pipe_out[i]);

        if (pipe_err[i] != nullptr)

            CloseHandle(pipe_err[i]);

    }

    return nullptr;

}

/************************************************************************/

/*                  CPLSpawnAsyncGetChildProcessId()                    */

/************************************************************************/

CPL_PID CPLSpawnAsyncGetChildProcessId(CPLSpawnedProcess *p)

{

    return p->nProcessId;

}

/************************************************************************/

/*                        CPLSpawnAsyncFinish()                         */

/************************************************************************/

int CPLSpawnAsyncFinish(CPLSpawnedProcess *p, int bWait, int /* bKill */)

{

    // Get the exit code.

    DWORD exitCode = -1;

    if (bWait)

    {

        WaitForSingleObject(p->hProcess, INFINITE);

        GetExitCodeProcess(p->hProcess, &exitCode);

    }

    else

    {

        exitCode = 0;

    }

    CloseHandle(p->hProcess);

    CloseHandle(p->hThread);

    CPLSpawnAsyncCloseInputFileHandle(p);

    CPLSpawnAsyncCloseOutputFileHandle(p);

    CPLSpawnAsyncCloseErrorFileHandle(p);

    CPLFree(p);

    return static_cast<int>(exitCode);

}

/************************************************************************/

/*                 CPLSpawnAsyncCloseInputFileHandle()                  */

/************************************************************************/

void CPLSpawnAsyncCloseInputFileHandle(CPLSpawnedProcess *p)

{

    if (p->fin != nullptr)

        CloseHandle(p->fin);

    p->fin = nullptr;

}

/************************************************************************/

/*                 CPLSpawnAsyncCloseOutputFileHandle()                 */

/************************************************************************/

void CPLSpawnAsyncCloseOutputFileHandle(CPLSpawnedProcess *p)

{

    if (p->fout != nullptr)

        CloseHandle(p->fout);

    p->fout = nullptr;

}

/************************************************************************/

/*                 CPLSpawnAsyncCloseErrorFileHandle()                  */

/************************************************************************/

void CPLSpawnAsyncCloseErrorFileHandle(CPLSpawnedProcess *p)

{

    if (p->ferr != nullptr)

        CloseHandle(p->ferr);

    p->ferr = nullptr;

}

#else  // Not WIN32

/************************************************************************/

/*                          CPLPipeRead()                               */

/************************************************************************/

/**

 * Read data from the standard output of a forked process.

 *

 * @param fin handle returned by CPLSpawnAsyncGetInputFileHandle().

 * @param data buffer in which to write.

 * @param length number of bytes to read.

 *

 * @return TRUE in case of success.

 *

 * @since GDAL 1.10.0

 */

int CPLPipeRead(CPL_FILE_HANDLE fin, void *data, int length)

{

    GByte *pabyData = static_cast<GByte *>(data);

    int nRemain = length;

    while (nRemain > 0)

    {

        while (true)

        {

            // coverity[overflow_sink]

            const ssize_t n = read(fin, pabyData, nRemain);

            if (n < 0)

            {

                if (errno == EINTR)

                    continue;

                else

                    return FALSE;

            }

            else if (n == 0)

                return FALSE;

            pabyData += n;

            assert(n <= nRemain);

            nRemain -= static_cast<int>(n);

            break;

        }

    }

    return TRUE;

}

/************************************************************************/

/*                          CPLPipeWrite()                              */

/************************************************************************/

/**

 * Write data to the standard input of a forked process.

 *

 * @param fout handle returned by CPLSpawnAsyncGetOutputFileHandle().

 * @param data buffer from which to read.

 * @param length number of bytes to write.

 *

 * @return TRUE in case of success.

 *

 * @since GDAL 1.10.0

 */

int CPLPipeWrite(CPL_FILE_HANDLE fout, const void *data, int length)

{

    const GByte *pabyData = static_cast<const GByte *>(data);

    int nRemain = length;

    while (nRemain > 0)

    {

        while (true)

        {

            // coverity[overflow_sink]

            const ssize_t n = write(fout, pabyData, nRemain);

            if (n < 0)

            {

                if (errno == EINTR)

                    continue;

                else

                    return FALSE;

            }

            pabyData += n;

            assert(n <= nRemain);

            nRemain -= static_cast<int>(n);

            break;

        }

    }

    return TRUE;

}

/************************************************************************/

/*                          FillFileFromPipe()                              */

/************************************************************************/

static void FillFileFromPipe(CPL_FILE_HANDLE pipe_fd, VSILFILE *fout)

{

    char buf[PIPE_BUFFER_SIZE] = {};

    while (true)

    {

        const int nRead =

            static_cast<int>(read(pipe_fd, buf, PIPE_BUFFER_SIZE));

        if (nRead <= 0)

            break;

        const int nWritten = static_cast<int>(VSIFWriteL(buf, 1, nRead, fout));

        if (nWritten < nRead)

            break;

    }

}

/************************************************************************/

/*                            CPLSpawnAsync()                           */

/************************************************************************/

struct _CPLSpawnedProcess

{

    pid_t pid;

    CPL_FILE_HANDLE fin;

    CPL_FILE_HANDLE fout;

    CPL_FILE_HANDLE ferr;

#ifdef HAVE_POSIX_SPAWNP

    bool bFreeActions;

    posix_spawn_file_actions_t actions;

#endif

};

/**

 * Runs an executable in another process (or fork the current process)

 * and return immediately.

 *

 * This function launches an executable and returns immediately, while letting

 * the sub-process to run asynchronously.

 *

 * It is implemented as CreateProcess() on Windows platforms, and fork()/exec()

 * on other platforms.

 *

 * On Unix, a pointer of function can be provided to run in the child process,

 * without exec()'ing a new executable.

 *

 * @param pfnMain the function to run in the child process (Unix only).

 * @param papszArgv argument list of the executable to run. papszArgv[0] is the

 *                  name of the executable.

 * @param bCreateInputPipe set to TRUE to create a pipe for the child

 * input stream.

 * @param bCreateOutputPipe set to TRUE to create a pipe for the child

 * output stream.

 * @param bCreateErrorPipe set to TRUE to create a pipe for the child

 * error stream.

 * @param papszOptions unused. should be set to NULL.

 *

 * @return a handle, that must be freed with CPLSpawnAsyncFinish()

 *

 * @since GDAL 1.10.0

 */

CPLSpawnedProcess *

CPLSpawnAsync(int (*pfnMain)(CPL_FILE_HANDLE, CPL_FILE_HANDLE),

              const char *const papszArgv[], int bCreateInputPipe,

              int bCreateOutputPipe, int bCreateErrorPipe,

              CPL_UNUSED char **papszOptions)

{

    int pipe_in[2] = {-1, -1};

    int pipe_out[2] = {-1, -1};

    int pipe_err[2] = {-1, -1};

    if ((bCreateInputPipe && pipe(pipe_in)) ||

        (bCreateOutputPipe && pipe(pipe_out)) ||

        (bCreateErrorPipe && pipe(pipe_err)))

    {

        CPLError(CE_Failure, CPLE_AppDefined, "Could not create pipe");

        return nullptr;

    }

    bool bDup2In = CPL_TO_BOOL(bCreateInputPipe);

    bool bDup2Out = CPL_TO_BOOL(bCreateOutputPipe);

    bool bDup2Err = CPL_TO_BOOL(bCreateErrorPipe);

    char **papszArgvDup = CSLDuplicate(const_cast<char **>(papszArgv));

    // If we don't do any file actions, posix_spawnp() might be implemented

    // efficiently as a vfork()/exec() pair (or if it is not available, we

    // can use vfork()/exec()), so if the child is cooperative

    // we pass the pipe handles as commandline arguments.

    if (papszArgv != nullptr)

    {

        for (int i = 0; papszArgvDup[i] != nullptr; i++)

        {

            if (bCreateInputPipe && strcmp(papszArgvDup[i], "{pipe_in}") == 0)

            {

                CPLFree(papszArgvDup[i]);

                papszArgvDup[i] = CPLStrdup(CPLSPrintf(

                    "%d,%d", pipe_in[IN_FOR_PARENT], pipe_in[OUT_FOR_PARENT]));

                bDup2In = false;

            }

            else if (bCreateOutputPipe &&

                     strcmp(papszArgvDup[i], "{pipe_out}") == 0)

            {

                CPLFree(papszArgvDup[i]);

                papszArgvDup[i] =

                    CPLStrdup(CPLSPrintf("%d,%d", pipe_out[OUT_FOR_PARENT],

                                         pipe_out[IN_FOR_PARENT]));

                bDup2Out = false;

            }

            else if (bCreateErrorPipe &&

                     strcmp(papszArgvDup[i], "{pipe_err}") == 0)

            {

                CPLFree(papszArgvDup[i]);

                papszArgvDup[i] =

                    CPLStrdup(CPLSPrintf("%d,%d", pipe_err[OUT_FOR_PARENT],

                                         pipe_err[IN_FOR_PARENT]));

                bDup2Err = false;

            }

        }

    }

#ifdef HAVE_POSIX_SPAWNP

    if (papszArgv != nullptr)

    {

        bool bHasActions = false;

        posix_spawn_file_actions_t actions;

        if (bDup2In)

        {

            /*if( !bHasActions )*/ posix_spawn_file_actions_init(&actions);

            posix_spawn_file_actions_adddup2(&actions, pipe_in[IN_FOR_PARENT],

                                             fileno(stdin));

            posix_spawn_file_actions_addclose(&actions,

                                              pipe_in[OUT_FOR_PARENT]);

            bHasActions = true;

        }

        if (bDup2Out)

        {

            if (!bHasActions)

                posix_spawn_file_actions_init(&actions);

            posix_spawn_file_actions_adddup2(&actions, pipe_out[OUT_FOR_PARENT],

                                             fileno(stdout));

            posix_spawn_file_actions_addclose(&actions,

                                              pipe_out[IN_FOR_PARENT]);

            bHasActions = true;

        }

        if (bDup2Err)

        {

            if (!bHasActions)

                posix_spawn_file_actions_init(&actions);

            posix_spawn_file_actions_adddup2(&actions, pipe_err[OUT_FOR_PARENT],

                                             fileno(stderr));

            posix_spawn_file_actions_addclose(&actions,

                                              pipe_err[IN_FOR_PARENT]);

            bHasActions = true;

        }

        pid_t pid = 0;

        assert(papszArgvDup[0] != nullptr);

        if (posix_spawnp(&pid, papszArgvDup[0],

                         bHasActions ? &actions : nullptr, nullptr,

                         papszArgvDup, environ) != 0)

        {

            if (bHasActions)

                posix_spawn_file_actions_destroy(&actions);

            CPLError(CE_Failure, CPLE_AppDefined, "posix_spawnp() failed");

            CSLDestroy(papszArgvDup);

            for (int i = 0; i < 2; i++)

            {

                if (pipe_in[i] >= 0)

                    close(pipe_in[i]);

                if (pipe_out[i] >= 0)

                    close(pipe_out[i]);

                if (pipe_err[i] >= 0)

                    close(pipe_err[i]);

            }

            return nullptr;

        }

        CSLDestroy(papszArgvDup);

        // Close unused end of pipe.

        if (bCreateInputPipe)

            close(pipe_in[IN_FOR_PARENT]);

        if (bCreateOutputPipe)

            close(pipe_out[OUT_FOR_PARENT]);

        if (bCreateErrorPipe)

            close(pipe_err[OUT_FOR_PARENT]);

            // Ignore SIGPIPE.

#ifdef SIGPIPE

        std::signal(SIGPIPE, SIG_IGN);

#endif

        CPLSpawnedProcess *p = static_cast<CPLSpawnedProcess *>(

            CPLMalloc(sizeof(CPLSpawnedProcess)));

        if (bHasActions)

            memcpy(&p->actions, &actions, sizeof(actions));

        p->bFreeActions = bHasActions;

        p->pid = pid;

        p->fin = pipe_out[IN_FOR_PARENT];

        p->fout = pipe_in[OUT_FOR_PARENT];

        p->ferr = pipe_err[IN_FOR_PARENT];

        return p;

    }

#endif  // #ifdef HAVE_POSIX_SPAWNP

    pid_t pid = 0;

#if defined(HAVE_VFORK) && !defined(HAVE_POSIX_SPAWNP)

    if (papszArgv != nullptr && !bDup2In && !bDup2Out && !bDup2Err)

    {

        // Workaround clang static analyzer warning about unsafe use of vfork.

        pid_t (*p_vfork)(void) = vfork;

        pid = p_vfork();

    }

    else

#endif

    {

        pid = fork();

    }

    if (pid == 0)

    {

        // Close unused end of pipe.

        if (bDup2In)

            close(pipe_in[OUT_FOR_PARENT]);

        if (bDup2Out)

            close(pipe_out[IN_FOR_PARENT]);

        if (bDup2Err)

            close(pipe_err[IN_FOR_PARENT]);

#ifndef HAVE_POSIX_SPAWNP

        if (papszArgv != nullptr)

        {

            if (bDup2In)

                dup2(pipe_in[IN_FOR_PARENT], fileno(stdin));

            if (bDup2Out)

                dup2(pipe_out[OUT_FOR_PARENT], fileno(stdout));

            if (bDup2Err)

                dup2(pipe_err[OUT_FOR_PARENT], fileno(stderr));

            execvp(papszArgvDup[0], papszArgvDup);

            _exit(1);

        }

        else

#endif  // HAVE_POSIX_SPAWNP

        {

            if (bCreateErrorPipe)

                close(pipe_err[OUT_FOR_PARENT]);

            int nRet = 0;

            if (pfnMain != nullptr)

                nRet = pfnMain(bCreateInputPipe ? pipe_in[IN_FOR_PARENT]

                                                : fileno(stdin),

                               bCreateOutputPipe ? pipe_out[OUT_FOR_PARENT]

                                                 : fileno(stdout));

            _exit(nRet);

        }

    }

    else if (pid > 0)

    {

        CSLDestroy(papszArgvDup);

        // Close unused end of pipe.

        if (bCreateInputPipe)

            close(pipe_in[IN_FOR_PARENT]);

        if (bCreateOutputPipe)

            close(pipe_out[OUT_FOR_PARENT]);

        if (bCreateErrorPipe)

            close(pipe_err[OUT_FOR_PARENT]);

            // Ignore SIGPIPE.

#ifdef SIGPIPE

        std::signal(SIGPIPE, SIG_IGN);

#endif

        CPLSpawnedProcess *p = static_cast<CPLSpawnedProcess *>(

            CPLMalloc(sizeof(CPLSpawnedProcess)));

#ifdef HAVE_POSIX_SPAWNP

        p->bFreeActions = false;

#endif

        p->pid = pid;

        p->fin = pipe_out[IN_FOR_PARENT];

        p->fout = pipe_in[OUT_FOR_PARENT];

        p->ferr = pipe_err[IN_FOR_PARENT];

        return p;

    }

    CPLError(CE_Failure, CPLE_AppDefined, "Fork failed");

    CSLDestroy(papszArgvDup);

    for (int i = 0; i < 2; i++)

    {

        if (pipe_in[i] >= 0)

            close(pipe_in[i]);

        if (pipe_out[i] >= 0)

            close(pipe_out[i]);

        if (pipe_err[i] >= 0)

            close(pipe_err[i]);

    }

    return nullptr;

}

/************************************************************************/

/*                  CPLSpawnAsyncGetChildProcessId()                    */

/************************************************************************/

CPL_PID CPLSpawnAsyncGetChildProcessId(CPLSpawnedProcess *p)

{

    return p->pid;

}

/************************************************************************/

/*                        CPLSpawnAsyncFinish()                         */

/************************************************************************/

/**

 * \fn CPLSpawnAsyncFinish(CPLSpawnedProcess*,int,int)

 * Wait for the forked process to finish.

 *

 * @param p handle returned by CPLSpawnAsync()

 * @param bWait set to TRUE to wait for the child to terminate. Otherwise the

 *              associated handles are just cleaned.

 * @param bKill set to TRUE to force child termination (unimplemented right

 *              now).

 *

 * @return the return code of the forked process if bWait == TRUE, 0 otherwise

 *

 * @since GDAL 1.10.0

 */

int CPLSpawnAsyncFinish(CPLSpawnedProcess *p, int bWait, CPL_UNUSED int bKill)

{

    int status = 0;

    if (bWait)

    {

        while (true)

        {

            status = -1;

            const int ret = waitpid(p->pid, &status, 0);

            if (ret < 0)

            {

                if (errno != EINTR)

                {

                    break;

                }

            }

            else

            {

                if (WIFEXITED(status))

                {

                    status = WEXITSTATUS(status);

                }

                else

                {

                    status = -1;

                }

                break;

            }

        }

    }

    CPLSpawnAsyncCloseInputFileHandle(p);

    CPLSpawnAsyncCloseOutputFileHandle(p);

    CPLSpawnAsyncCloseErrorFileHandle(p);

#ifdef HAVE_POSIX_SPAWNP

    if (p->bFreeActions)

        posix_spawn_file_actions_destroy(&p->actions);

#endif

    CPLFree(p);

    return status;

}

/************************************************************************/

/*                 CPLSpawnAsyncCloseInputFileHandle()                  */

/************************************************************************/

void CPLSpawnAsyncCloseInputFileHandle(CPLSpawnedProcess *p)

{

    if (p->fin >= 0)

        close(p->fin);

    p->fin = -1;

}

/************************************************************************/

/*                 CPLSpawnAsyncCloseOutputFileHandle()                 */

/************************************************************************/

void CPLSpawnAsyncCloseOutputFileHandle(CPLSpawnedProcess *p)

{

    if (p->fout >= 0)

        close(p->fout);

    p->fout = -1;

}

/************************************************************************/

/*                 CPLSpawnAsyncCloseErrorFileHandle()                  */

/************************************************************************/

void CPLSpawnAsyncCloseErrorFileHandle(CPLSpawnedProcess *p)

{

    if (p->ferr >= 0)

        close(p->ferr);

    p->ferr = -1;

}

#endif

/************************************************************************/

/*                    CPLSpawnAsyncGetInputFileHandle()                 */

/************************************************************************/

/**

 * Return the file handle of the standard output of the forked process

 * from which to read.

 *

 * @param p handle returned by CPLSpawnAsync().

 *

 * @return the file handle.

 *

 * @since GDAL 1.10.0

 */

CPL_FILE_HANDLE CPLSpawnAsyncGetInputFileHandle(CPLSpawnedProcess *p)

{

    return p->fin;

}

/************************************************************************/

/*                   CPLSpawnAsyncGetOutputFileHandle()                 */

/************************************************************************/

/**

 * Return the file handle of the standard input of the forked process

 * into which to write

 *

 * @param p handle returned by CPLSpawnAsync().

 *

 * @return the file handle.

 *

 * @since GDAL 1.10.0

 */

CPL_FILE_HANDLE CPLSpawnAsyncGetOutputFileHandle(CPLSpawnedProcess *p)

{

    return p->fout;

}

/************************************************************************/

/*                    CPLSpawnAsyncGetErrorFileHandle()                 */

/************************************************************************/

/**

 * Return the file handle of the standard error of the forked process

 * from which to read.

 *

 * @param p handle returned by CPLSpawnAsync().

 *

 * @return the file handle

 *

 * @since GDAL 1.10.0

 */

CPL_FILE_HANDLE CPLSpawnAsyncGetErrorFileHandle(CPLSpawnedProcess *p)

{

    return p->ferr;

}