path: root/src/execute.cc

// -*- c++ -*-
// Distributed under the BSD 2-Clause License.
// See accompanying file LICENSE for details.
#include "execute.h"

#include "ctor.h"

#if !defined(_WIN32)
	#include <unistd.h>
	#include <sys/types.h>
	#include <sys/wait.h>
	#include <spawn.h>
#else
	#define WINDOWS_LEAN_AND_MEAN
	#include <windows.h>
	#undef max
#endif

#include <iostream>
#include <cstring>
#include <vector>
#include <deque>
#include <filesystem>

/*
https://blog.famzah.net/2009/11/20/a-much-faster-popen-and-system-implementation-for-linux/
https://github.com/famzah/popen-noshell/commit/1f9eaf4eeef348d1efe0f3c7fe8ab670653cfbb1
https://blog.famzah.net/2018/12/19/posix_spawn-performance-benchmarks-and-usage-examples/
https://stackoverflow.com/questions/4259629/what-is-the-difference-between-fork-and-vfork/5207945#5207945
 */


namespace
{
class Env
	: public std::vector<char*>
{
public:
	Env(const std::vector<std::string>& args)
	{
		for(const auto& arg : args)
		{
#if !defined(_WIN32)
			push_back(strdup(arg.data()));
#else
			push_back(_strdup(arg.data()));
#endif
		}
		push_back(nullptr);
	}

	~Env()
	{
		for(auto ptr : *this)
		{
			free(ptr);
		}
	}
};

#if !defined(_WIN32)
int parent_waitpid(pid_t pid)
{
	int status{};

	if(waitpid(pid, &status, 0) != pid)
	{
		return 1;
	}

	return WEXITSTATUS(status);
}
#endif //_WIN32
} // namespace ::

extern char **environ; // see 'man environ'

int execute(const ctor::settings& settings,
            const std::string& command,
            const std::vector<std::string>& args,
            const std::map<std::string, std::string>& env,
            [[maybe_unused]] bool terminate)
{
	std::vector<const char*> argv;
	argv.push_back(command.data());
	for(const auto& arg : args)
	{
		argv.push_back(arg.data());
	}
	argv.push_back(nullptr);

	std::string cmd;
	for(const auto& arg : argv)
	{
		if(arg == nullptr)
		{
			break;
		}
		if(!cmd.empty())
		{
			cmd += " ";
		}
		cmd += arg;
	}

	if(settings.verbose)
	{
		std::cout << cmd << std::endl;
	}

#if !defined(_WIN32)

#if 1
	auto pid = vfork();
	if(pid == 0)
	{
		std::vector<std::string> venv;
		for(const auto& [key, value] : env)
		{
			venv.push_back(key + "=" + value);
		}

		for(auto current = environ; *current; ++current)
		{
			venv.emplace_back(*current);
		}

		Env penv(venv);
		execve(command.data(), (char**)argv.data(), penv.data());
		std::cout << "Could not execute " << command << ": " <<
			strerror(errno) << "\n";
		_exit(1); // execve only returns if an error occurred
	}
	return parent_waitpid(pid);
#elif 0
	pid_t pid;
	std::vector<std::string> venv;
	for(const auto& [key, value] : env)
	{
		venv.push_back(key + "=" + value);
	}
	Env penv(venv);
	if(posix_spawn(&pid, command.data(), nullptr, nullptr,
	               (char**)argv.data(), penv.data()))
	{
		return 1;
	}
	return parent_waitpid(pid);
#else
	(void)parent_waitpid;
	return system(cmd.data());
#endif

#else // _WIN32
	std::map<std::string, std::string> new_env;
	{
		auto env_strings = GetEnvironmentStrings();
		const char* ptr = env_strings;
		std::string key;
		std::string value;
		bool key_state{true};
		while(true)
		{
			if(key_state) // searching for key
			{
				if(*ptr == '\0')
				{
					break;
				}

				if(*ptr != '=')
				{
					key += *ptr;
				}
				else
				{
					key_state = false;
				}
			}
			else
			{
				if(*ptr != '\0')
				{
					value += *ptr;
				}
				else
				{
					new_env.insert({key, value});
					key = {};
					value = {};
					key_state = true;
				}
			}
		++ptr;
		}
		FreeEnvironmentStrings(env_strings);
	}

	// add new env vars (if any)
	for(const auto& [key, value] : env)
	{
		//if(key == "CL" || key == "LINK" || key == "LIB")
		{
			new_env[key] = value;
		}
	}

	std::string env_str;
	for(const auto& [k,v] : new_env)
	{
		env_str += k + "=" + v;
		env_str += '\0';
	}
	env_str += '\0';

	STARTUPINFO si{};
//	si.hStdInput = GetStdHandle(((DWORD)-10)/*STD_INPUT_HANDLE*/);
//	si.hStdOutput = GetStdHandle(((DWORD)-11)/*STD_OUTPUT_HANDLE*/);
//	si.hStdError = GetStdHandle(((DWORD)-12)/*STD_ERROR_HANDLE*/);
//	si.dwFlags = /*STARTF_USESTDHANDLES*/0x00000100;

	PROCESS_INFORMATION pi{};

	si.cb = sizeof(si);

	// TODO: Use SetDllDirectory(...) to set DLL search directory

	if(terminate)
	{
		char tmpdir[MAX_PATH+1];
		int cnt{0};

		// The returned string ends with a backslash
		if(GetTempPathA(sizeof(tmpdir), tmpdir) == 0)
		{
			std::cerr << "Could not read TMP folder\n";
			return GetLastError();
		}

		char source[MAX_PATH];
		HMODULE module = GetModuleHandle(0);
		GetModuleFileNameA(module, source, MAX_PATH);

		while(true)
		{
			if(cnt > 10) // If we need to try more than 10 times something is wrong
			{
				return 1;
			}

			std::filesystem::path tmp_file = settings.builddir;
			tmp_file /= "tmp";
			std::string target = tmp_file.string() + "-" + std::to_string(cnt);
			std::cout << "move " << source << " => " << target <<std::endl;
			if(MoveFileA(source, target.data()))
			{
				break; // success
			}

			auto err = GetLastError();
			if(err == ERROR_ALREADY_EXISTS)
			{
				if(DeleteFileA(target.data()))
				{
					continue; // Try again
				}

				err = GetLastError();
				if(err != ERROR_ACCESS_DENIED)
				{
					std::cerr << "Could not delete file\n";
					return err;
				}

				cnt++;
				continue; // Increment and try again
			}
			else
			{
				std::cerr << "Could not move file\n";
				return err;
			}
		}
	}

	if(!CreateProcess(nullptr,           // lpApplicationName
	                  (char*)cmd.data(), // lpCommandLine
	                  nullptr,           // lpProcessAttributes
	                  nullptr,           // lpThreadAttributes
	                  TRUE,              // bInheritHandles
	                  INHERIT_PARENT_AFFINITY |
	                  //DETACHED_PROCESS |
	                  ///*DEBUG_PROCESS*/ 0x00000001 |
	                  ///*CREATE_NO_WINDOW*/ 0x08000000 |
	                  ///*CREATE_BREAKAWAY_FROM_JOB*/ 0x01000000 |
	                  /*CREATE_NEW_PROCESS_GROUP*/ 0x00000200 |
	                  0,                 // dwCreationFlags
	                  env_str.data(),    // lpEnvironment
	                  nullptr,           // lpCurrentDirectory
	                  &si,               // lpStartupInfo
	                  &pi))              // lpProcessInformation
	{
		return 1; // Could not start process;
	}

	// Now 'pi.hProcess' contains the process HANDLE, which you can use to
	// wait for it like this:
	const DWORD infinite = 0xFFFFFFFF;
	WaitForSingleObject(pi.hProcess, infinite);
	DWORD exitCode{0};
	GetExitCodeProcess(pi.hProcess, &exitCode);
	return exitCode;
#endif // _WIN32

	return 1;
}