ShellCommand: automatic wait call in destructor (#1210)

* ShellCommand: automatic wait call in destructor

* ShellCommand: tryWait in destructor

* Update ShellCommand.cpp

* Update ShellCommand.cpp

dbms/src/Common/ShellCommand.cpp

@@ -76,6 +76,11 @@ namespace
 namespace DB
 {
 
+ShellCommand::~ShellCommand()
+{
+    if (!wait_called)
+        tryWait();
+}
 
 std::unique_ptr<ShellCommand> ShellCommand::executeImpl(const char * filename, char * const argv[], bool pipe_stdin_only)
 {
@@ -176,6 +181,8 @@ std::unique_ptr<ShellCommand> ShellCommand::executeDirect(const std::string & pa
 
 int ShellCommand::tryWait()
 {
+    wait_called = true;
+
     int status = 0;
     if (-1 == waitpid(pid, &status, 0))
         throwFromErrno("Cannot waitpid", ErrorCodes::CANNOT_WAITPID);

dbms/src/Common/ShellCommand.h

@@ -27,6 +27,7 @@ class ShellCommand
 {
 private:
     pid_t pid;
+    bool wait_called = false;
 
     ShellCommand(pid_t pid, int in_fd, int out_fd, int err_fd)
         : pid(pid), in(in_fd), out(out_fd), err(err_fd) {};
@@ -38,6 +39,8 @@ public:
     ReadBufferFromFile out;
     ReadBufferFromFile err;
 
+    ~ShellCommand();
+
     /// Run the command using /bin/sh -c
     static std::unique_ptr<ShellCommand> execute(const std::string & command, bool pipe_stdin_only = false);
 

dbms/src/Common/tests/shell_command_test.cpp

@@ -5,6 +5,8 @@
 #include <IO/WriteBufferFromFileDescriptor.h>
 #include <IO/ReadBufferFromString.h>
 
+#include <chrono>
+#include <thread>
 
 using namespace DB;
 
@@ -43,6 +45,15 @@ try
 
         command->wait();
     }
+
+    // <defunct> hunting:
+    for (int i = 0; i < 1000; ++i) {
+        auto command = ShellCommand::execute("echo " + std::to_string(i));
+        //command->wait(); // now automatic
+    }
+
+    // std::cerr << "inspect me: ps auxwwf" << "\n";
+    // std::this_thread::sleep_for(std::chrono::seconds(100));
 }
 catch (...)
 {