Group process waiting on windows

[andrejnau]

I wrote a few examples and checked on macOS 10.12.2 (clang-800.0.42.1) and Windows 10 (msvc 2017)

#include <boost/process.hpp>
#include <iostream>
#include <chrono>
#include <map>

namespace bp = boost::process;

int main()
{
	std::map<int, bp::child> q;
	bp::group g;

	for (int i = 1; i <= 5; ++i)
	{
#ifdef _WIN32
		std::string exe = "powershell";
		std::vector<std::string> args =
		{
			"-command",
			"Start-Sleep",
			"-s",
			std::to_string(i),
			";",
			"echo",
			std::to_string(i)
		};
#else
		std::string exe = "sleep";
		std::vector<std::string> args =
		{
			std::to_string(i),
			";",
			"echo",
			std::to_string(i)
		};
#endif
		q[i] = bp::child(
			bp::exe = exe,
			bp::args = args,
			bp::shell,
			g,
			bp::std_out > stdout);
	}

	while (!q.empty())
	{
		g.wait();
		for (auto it = q.begin(); it != q.end(); )
		{
			bp::child& c = it->second;
			if (!c.running())
			{
				std::cout << "exit " << it->first << std::endl;
				it = q.erase(it);
			}
			else
			{
				++it;
			}
		}
	}
}

This code works on macOS, but on Windows hangs on the line g.wait();

I rewrite this code without use bp::group

#include <boost/process.hpp>
#include <iostream>
#include <chrono>
#include <map>

namespace bp = boost::process;

int main()
{
	std::map<int, bp::child> q;

	for (int i = 1; i <= 5; ++i)
	{
#ifdef _WIN32
		std::string exe = "powershell";
		std::vector<std::string> args =
		{
			"-command",
			"Start-Sleep",
			"-s",
			std::to_string(i),
			";",
			"echo",
			std::to_string(i)
		};
#else
		std::string exe = "sleep";
		std::vector<std::string> args =
		{
			std::to_string(i),
			";",
			"echo",
			std::to_string(i)
		};
#endif
		q[i] = bp::child(
			bp::exe = exe,
			bp::args = args,
			bp::shell,
			bp::std_out > stdout);
	}

	while (!q.empty())
	{
		for (auto it = q.begin(); it != q.end(); )
		{
			bp::child& c = it->second;

			std::error_code ec;
			c.wait_for(std::chrono::milliseconds(100), ec);
			if (!c.running(ec))
			{
				std::cout << "exit " << it->first << std::endl;
				it = q.erase(it);
			}
			else
			{
				++it;
			}
		}
		std::this_thread::sleep_for(std::chrono::milliseconds(100));
	}
}

Now, i have a problem on macOS. I get following output:

exit 1
1
exit 2
exit 3
exit 4
2
exit 5
4
5

If I removec.wait_for(std::chrono::milliseconds(100), ec);
I will get the correct output:

1
exit 1
2
exit 2
3
exit 3
4
exit 4
5
exit 5

I think the problem is that _exit_status->store(exit_code) in wait_for it is called if boost::process::detail::api::wait_for ended with an error

[andrejnau]

Also this code

#include <boost/process.hpp>

namespace bp = boost::process;

int main()
{
	bp::child c = bp::child(
		"echo hello",
		bp::shell,
		bp::std_out > stdout);
	c.wait();
}

not work on macOS. I get following output /bin/sh: echo hello: command not found
But it work on Windows

[klemens-morgenstern]

The second issue should be fixed, it just worked for me. Which commit did you use?

[klemens-morgenstern]

I think the problem is that _exit_status->store(exit_code) in wait_for it is called if boost::process::detail::api::wait_for ended with an error

Hmm, that might be the case, but I'm not sure. Are you able to try that one, i.e. replace return !time_out_occured; with return ret != -1.
I am not sure why I use the timeout there, it looks like a bug. Does seem to be different on windows too.

[klemens-morgenstern]

The group.wait is in fact broken on windows. I will have to add a completion port for that which might take a while. I really do not have a test for that.

I'll let you know when I get around to working on that.

[andrejnau]

The second issue should be fixed, it just worked for me. Which commit did you use?

I check on last commit. It work without use bp::shell, but with bp::shell i get /bin/sh: echo hello: command not found

[klemens-morgenstern]

Oh, I thought it failed to compile on windows, that's what I checked for.

[andrejnau]

Are you able to try that one, i.e. replace return !time_out_occured; with return ret != -1.

Yes, it helps to solve the problem.

[klemens-morgenstern]

Alright, I'll get that one in and will mark group.wait* as broken for the 1.64 release.

[andrejnau]

I check on last commit. It work without use bp::shell, but with bp::shell i get /bin/sh: echo hello: command not found

It was broken on commit c31f697, after this commit exe_cmd_init::cmd_shell generate incorrect command
/bin/sh -c "\"echo hello\""

[andrejnau]

This code should threw the exception?

#include <boost/process.hpp>
#include <boost/process/extend.hpp>

namespace bp = boost::process;

int main()
{
	bp::child c = bp::child(
		"incorrect.exe",
		bp::extend::on_error([](auto&, const std::error_code& ec)
		{
			//...
		})
	);
	c.wait();
}

I expect that on_error callback is invoked, but throw exception.
Is this the correct behavior? I can pass in the constructor std::error_code. But it seems to me that if there is on_error callback, this is not entirely correct.

[klemens-morgenstern]

Alright, I'll check that the constructed command is done right. There was some issue with the quotes, I remember that.

[klemens-morgenstern]

Actually that should throw, the behaviour shuold only be influences by passing an std::error_code or ignore_error to the function.