Merge branch '11.6' into 'master'11.6

add upstream 11.6

See merge request opensource-tracking/FreeFileSync!30

1 files changed, 249 insertions, 0 deletions

diff --git a/zen/process_exec.cpp b/zen/process_exec.cpp
new file mode 100644
index 00000000..bbc87c51
--- /dev/null
+++ b/zen/process_exec.cpp
@@ -0,0 +1,249 @@
+// *****************************************************************************
+// * This file is part of the FreeFileSync project. It is distributed under    *
+// * GNU General Public License: https://www.gnu.org/licenses/gpl-3.0          *
+// * Copyright (C) Zenju (zenju AT freefilesync DOT org) - All Rights Reserved *
+// *****************************************************************************
+
+#include "process_exec.h"
+#include <chrono>
+#include "guid.h"
+#include "file_access.h"
+#include "file_io.h"
+
+    #include <unistd.h> //fork, pipe
+    #include <sys/wait.h> //waitpid
+    #include <fcntl.h>
+
+using namespace zen;
+
+
+Zstring zen::escapeCommandArg(const Zstring& arg)
+{
+//*INDENT-OFF*
+    Zstring output;
+    for (const Zchar c : arg)
+        switch (c)
+        {
+            case  '"': output += "\\\""; break; //Windows: not needed; " cannot be used as file name
+            case '\\': output += "\\\\"; break; //Windows: path separator! => don't escape
+            case '`':  output += "\\`";  break; //yes, used in some paths => Windows: no escaping required
+            default: output += c; break;
+        }
+//*INDENT-ON*
+    if (contains(output, Zstr(' ')))
+        output = Zstr('"') + output + Zstr('"'); //Windows: escaping a single blank instead would not work
+
+    return output;
+}
+
+
+
+
+namespace
+{
+std::pair<int /*exit code*/, std::string> processExecuteImpl(const Zstring& filePath, const std::vector<Zstring>& arguments,
+                                                             std::optional<int> timeoutMs) //throw SysError, SysErrorTimeOut
+{
+    const Zstring tempFilePath = appendSeparator(getTempFolderPath()) + //throw FileError
+                                 Zstr("FFS-") + utfTo<Zstring>(formatAsHexString(generateGUID()));
+    /*  can't use popen(): does NOT return the exit code on Linux (despite the documentation!), although it works correctly on macOS
+          => use pipes instead: https://linux.die.net/man/2/waitpid
+             bonus: no need for "2>&1" to redirect STDERR to STDOUT
+
+             What about premature exit via SysErrorTimeOut?
+                Linux: child process' end of the pipe *still works* even after the parent process is gone:
+                        There does not seem to be any output buffer size limit + no observable strain on system memory or disk space! :)
+                macOS: child process exits if parent end of pipe is closed: fuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuu..........
+
+       => solution: buffer output in temporary file
+
+       Unresolved problem: premature exit via SysErrorTimeOut (=> no waitpid()) creates zombie proceses:
+                "As long as a zombie is not removed from the system via a wait,
+                 it will consume a slot in the kernel process table, and if this table fills,
+                 it will not be possible to create further processes."                 */
+
+    const int EC_CHILD_LAUNCH_FAILED = 120; //avoid 127: used by the system, e.g. failure to execute due to missing .so file
+
+    //use O_TMPFILE? sounds nice, but support is probably crap: https://github.com/libvips/libvips/issues/1151
+    const int fdTempFile = ::open(tempFilePath.c_str(), O_CREAT | O_EXCL | O_RDWR | O_CLOEXEC,
+                                  S_IRUSR | S_IWUSR); //0600
+    if (fdTempFile == -1)
+        THROW_LAST_SYS_ERROR("open");
+    auto guardTmpFile = makeGuard<ScopeGuardRunMode::onExit>([&] { ::close(fdTempFile); });
+
+    //"deleting while handle is open" == FILE_FLAG_DELETE_ON_CLOSE
+    if (::unlink(tempFilePath.c_str()) != 0)
+        THROW_LAST_SYS_ERROR("unlink");
+
+    //--------------------------------------------------------------
+    //waitpid() is a useless pile of garbage without time out => check EOF from dummy pipe instead
+    int pipe[2] = {};
+    if (::pipe2(pipe, O_CLOEXEC) != 0)
+        THROW_LAST_SYS_ERROR("pipe2");
+
+
+    const int fdLifeSignR = pipe[0]; //for parent process
+    const int fdLifeSignW = pipe[1]; //for child process
+    ZEN_ON_SCOPE_EXIT(::close(fdLifeSignR));
+    auto guardFdLifeSignW = makeGuard<ScopeGuardRunMode::onExit>([&] { ::close(fdLifeSignW ); });
+    //--------------------------------------------------------------
+
+    //follow implemenation of ::system(): https://github.com/lattera/glibc/blob/master/sysdeps/posix/system.c
+    const pid_t pid = ::fork();
+    if (pid < 0) //pids are never negative, empiric proof: https://linux.die.net/man/2/wait
+        THROW_LAST_SYS_ERROR("fork");
+
+    if (pid == 0) //child process
+        try
+        {
+            //first task: set STDOUT redirection in case an error needs to be reported
+            if (::dup2(fdTempFile, STDOUT_FILENO) != STDOUT_FILENO) //O_CLOEXEC does NOT propagate with dup2()
+                THROW_LAST_SYS_ERROR("dup2(STDOUT)");
+
+            if (::dup2(fdTempFile, STDERR_FILENO) != STDERR_FILENO) //O_CLOEXEC does NOT propagate with dup2()
+                THROW_LAST_SYS_ERROR("dup2(STDERR)");
+
+            //avoid blocking scripts waiting for user input
+            // => appending " < /dev/null" is not good enough! e.g. hangs for: read -p "still hanging here"; echo fuuuuu...
+            const int fdDevNull = ::open("/dev/null", O_RDONLY | O_CLOEXEC);
+            if (fdDevNull == -1) //don't check "< 0" -> docu seems to allow "-2" to be a valid file handle
+                THROW_LAST_SYS_ERROR("open(/dev/null)");
+            ZEN_ON_SCOPE_EXIT(::close(fdDevNull));
+
+            if (::dup2(fdDevNull, STDIN_FILENO) != STDIN_FILENO) //O_CLOEXEC does NOT propagate with dup2()
+                THROW_LAST_SYS_ERROR("dup2(STDIN)");
+
+            //*leak* the fd and have it closed automatically on child process exit after execv()
+            if (::dup(fdLifeSignW) == -1) //O_CLOEXEC does NOT propagate with dup()
+                THROW_LAST_SYS_ERROR("dup(fdLifeSignW)");
+
+            std::vector<const char*> argv{ filePath.c_str() };
+            for (const Zstring& arg : arguments)
+                argv.push_back(arg.c_str());
+            argv.push_back(nullptr);
+
+            /*int rv =*/::execv(argv[0], const_cast<char**>(&argv[0])); //only returns if an error occurred
+            //safe to cast away const: https://pubs.opengroup.org/onlinepubs/9699919799/functions/exec.html
+            //  "The statement about argv[] and envp[] being constants is included to make explicit to future
+            //   writers of language bindings that these objects are completely constant. Due to a limitation of
+            //   the ISO C standard, it is not possible to state that idea in standard C."
+            THROW_LAST_SYS_ERROR("execv");
+        }
+        catch (const SysError& e)
+        {
+            ::puts(utfTo<std::string>(e.toString()).c_str());
+            ::fflush(stdout); //note: stderr is unbuffered by default
+            ::_exit(EC_CHILD_LAUNCH_FAILED); //[!] avoid flushing I/O buffers or doing other clean up from child process like with "exit()"!
+        }
+    //else: parent process
+
+
+    if (timeoutMs)
+    {
+        guardFdLifeSignW.dismiss();
+        ::close(fdLifeSignW); //[!] make sure we get EOF when fd is closed by child!
+
+        const int flags = ::fcntl(fdLifeSignR, F_GETFL);
+        if (flags == -1)
+            THROW_LAST_SYS_ERROR("fcntl(F_GETFL)");
+
+        if (::fcntl(fdLifeSignR, F_SETFL, flags | O_NONBLOCK) == -1)
+            THROW_LAST_SYS_ERROR("fcntl(F_SETFL, O_NONBLOCK)");
+
+
+        const auto endTime = std::chrono::steady_clock::now() + std::chrono::milliseconds(*timeoutMs);
+        for (;;) //EINTR handling? => allow interruption!?
+        {
+            //read until EAGAIN
+            char buf[16];
+            const ssize_t bytesRead = ::read(fdLifeSignR, buf, sizeof(buf));
+            if (bytesRead < 0)
+            {
+                if (errno != EAGAIN)
+                    THROW_LAST_SYS_ERROR("read");
+            }
+            else if (bytesRead > 0)
+                throw SysError(formatSystemError("read", L"", L"Unexpected data."));
+            else //bytesRead == 0: EOF
+                break;
+
+            //wait for stream input
+            const auto now = std::chrono::steady_clock::now();
+            if (now > endTime)
+                throw SysErrorTimeOut(_P("Operation timed out after 1 second.", "Operation timed out after %x seconds.", *timeoutMs / 1000));
+
+            const auto waitTimeMs = std::chrono::duration_cast<std::chrono::milliseconds>(endTime - now).count();
+
+            struct ::timeval tv = {};
+            tv.tv_sec  = static_cast<long>(waitTimeMs / 1000);
+            tv.tv_usec = static_cast<long>(waitTimeMs - tv.tv_sec * 1000) * 1000;
+
+            fd_set rfd = {}; //includes FD_ZERO
+            FD_SET(fdLifeSignR, &rfd);
+
+            if (const int rv = ::select(fdLifeSignR + 1, //int nfds
+                                        &rfd,            //fd_set* readfds
+                                        nullptr,         //fd_set* writefds
+                                        nullptr,         //fd_set* exceptfds
+                                        &tv);            //struct timeval* timeout
+                rv < 0)
+                THROW_LAST_SYS_ERROR("select");
+            else if (rv == 0)
+                throw SysErrorTimeOut(_P("Operation timed out after 1 second.", "Operation timed out after %x seconds.", *timeoutMs / 1000));
+        }
+    }
+
+    //https://linux.die.net/man/2/waitpid
+    int statusCode = 0;
+    if (::waitpid(pid,         //pid_t pid
+                  &statusCode, //int* status
+                  0) != pid)   //int options
+        THROW_LAST_SYS_ERROR("waitpid");
+
+
+    if (::lseek(fdTempFile, 0, SEEK_SET) != 0)
+        THROW_LAST_SYS_ERROR("lseek");
+
+    guardTmpFile.dismiss();
+    FileInput streamIn(fdTempFile, tempFilePath, nullptr /*notifyUnbufferedIO*/); //takes ownership!
+    std::string output = bufferedLoad<std::string>(streamIn); //throw FileError
+
+    if (!WIFEXITED(statusCode)) //signalled, crashed?
+        throw SysError(formatSystemError("waitpid", WIFSIGNALED(statusCode) ?
+                                         L"Killed by signal " + numberTo<std::wstring>(WTERMSIG(statusCode)) :
+                                         L"Exit status "      + numberTo<std::wstring>(statusCode),
+                                         utfTo<std::wstring>(trimCpy(output))));
+
+    const int exitCode = WEXITSTATUS(statusCode); //precondition: "WIFEXITED() == true"
+    if (exitCode == EC_CHILD_LAUNCH_FAILED || //child process should already have provided details to STDOUT
+        exitCode == 127) //details should have been streamed to STDERR: used by /bin/sh, e.g. failure to execute due to missing .so file
+        throw SysError(utfTo<std::wstring>(trimCpy(output)));
+
+    return { exitCode, output };
+}
+}
+
+
+std::pair<int /*exit code*/, Zstring> zen::consoleExecute(const Zstring& cmdLine, std::optional<int> timeoutMs) //throw SysError, SysErrorTimeOut
+{
+    const auto& [exitCode, output] = processExecuteImpl("/bin/sh", {"-c", cmdLine.c_str()}, timeoutMs); //throw SysError, SysErrorTimeOut
+    return {exitCode, copyStringTo<Zstring>(output)};
+}
+
+
+void zen::openWithDefaultApp(const Zstring& itemPath) //throw FileError
+{
+    try
+    {
+        const Zstring cmdTemplate = R"(xdg-open "%x")"; //doesn't block => no need for time out!
+        const Zstring cmdLine = replaceCpy(cmdTemplate, Zstr("%x"), itemPath);
+
+        if (const auto& [exitCode, output] = consoleExecute(cmdLine, std::nullopt /*timeoutMs*/); //throw SysError, (SysErrorTimeOut)
+            exitCode != 0)
+            throw SysError(formatSystemError(utfTo<std::string>(cmdTemplate),
+                                             replaceCpy(_("Exit code %x"), L"%x", numberTo<std::wstring>(exitCode)), utfTo<std::wstring>(output)));
+    }
+    catch (const SysError& e) { throw FileError(replaceCpy(_("Cannot open file %x."), L"%x", fmtPath(itemPath)), e.toString()); }
+}
+
+