From a02990beff549b9d768633eed1d81975a20ce35b Mon Sep 17 00:00:00 2001
From: SirLynix <lynix680@gmail.com>
Date: Tue, 23 Jan 2024 15:10:27 +0100
Subject: [PATCH] Core/Posix: Rework implementation (using posix_spawn)

---
 src/Nazara/Core/Posix/PosixUtils.cpp  |  6 +--
 src/Nazara/Core/Posix/ProcessImpl.cpp | 56 ++++++++++-----------------
 2 files changed, 24 insertions(+), 38 deletions(-)

diff --git a/src/Nazara/Core/Posix/PosixUtils.cpp b/src/Nazara/Core/Posix/PosixUtils.cpp
index 7bf84f354..69cf41651 100644
--- a/src/Nazara/Core/Posix/PosixUtils.cpp
+++ b/src/Nazara/Core/Posix/PosixUtils.cpp
@@ -24,7 +24,7 @@ namespace Nz::PlatformImpl
 		{
 			ret = ::close(fd);
 		}
-		while (ret != -1 || errno == EINTR);
+		while (ret == -1 && errno == EINTR);
 
 		return ret;
 #endif
@@ -37,7 +37,7 @@ namespace Nz::PlatformImpl
 		{
 			ret = ::read(fd, buf, count);
 		}
-		while (ret != -1 || errno == EINTR);
+		while (ret == -1 && errno == EINTR);
 
 		return ret;
 	}
@@ -49,7 +49,7 @@ namespace Nz::PlatformImpl
 		{
 			ret = ::write(fd, buf, count);
 		}
-		while (ret != -1 || errno == EINTR);
+		while (ret == -1 && errno == EINTR);
 
 		return ret;
 	}
diff --git a/src/Nazara/Core/Posix/ProcessImpl.cpp b/src/Nazara/Core/Posix/ProcessImpl.cpp
index 2b36dd711..2035c9886 100644
--- a/src/Nazara/Core/Posix/ProcessImpl.cpp
+++ b/src/Nazara/Core/Posix/ProcessImpl.cpp
@@ -9,6 +9,7 @@
 #include <NazaraUtils/StackArray.hpp>
 #include <cerrno>
 #include <cstdlib>
+#include <spawn.h>
 #include <unistd.h>
 #include <sys/wait.h>
 #include <Nazara/Core/Debug.hpp>
@@ -21,7 +22,7 @@ namespace Nz::PlatformImpl
 			return Ok(true);
 
 		if (errno == ESRCH)
-			return OK(false);
+			return Ok(false);
 
 		return Err(Error::GetLastSystemError());
 	}
@@ -43,9 +44,10 @@ namespace Nz::PlatformImpl
 		if (!pipe)
 			return Err("failed to create pipe: " + Error::GetLastSystemError());
 
+		std::filesystem::path fullpath = std::filesystem::absolute(program);
+
 		// Double fork (see https://0xjet.github.io/3OHA/2022/04/11/post.html)
 		// We will create a child and a grand-child process, using a pipe to retrieve the grand-child pid
-		// TODO: Maybe use vfork for the child process too?
 		// TODO: Use posix_spawn if possible instead
 		pid_t childPid = ::fork();
 		if (childPid == -1)
@@ -71,40 +73,24 @@ namespace Nz::PlatformImpl
 				}
 			}
 
-			pid_t grandChildPid = ::vfork();
-			if (grandChildPid == 0)
+			StackArray<char*> args = NazaraStackArrayNoInit(char*, arguments.size() + 2);
+
+			// It's safe to const_cast here as we're using a copy of the memory (from child) from the original process
+			args[0] = const_cast<char*>(program.c_str());
+			for (std::size_t i = 0; i < arguments.size(); ++i)
+				args[i + 1] = const_cast<char*>(arguments[i].data());
+
+			args.back() = nullptr;
+
+			char* envs[] = { nullptr };
+
+			pid_t grandChildPid;
+			if (posix_spawn(&grandChildPid, fullpath.c_str(), nullptr, nullptr, args.data(), envs) == 0)
 			{
-				// Grand-child process
-				StackArray<char*> argv = NazaraStackArrayNoInit(char*, arguments.size() + 2);
+				PidOrErr pid;
+				pid.pid = grandChildPid;
 
-				// It's safe to const_cast here as we're using a copy of the memory (from child) from the original process
-				argv[0] = const_cast<char*>(program.c_str());
-				for (std::size_t i = 0; i < arguments.size(); ++i)
-					argv[i + 1] = const_cast<char*>(arguments[i].data());
-
-				argv[argv.size() - 1] = nullptr;
-
-				char* envs[] = { nullptr };
-
-				::execve(program.c_str(), argv.data(), envs);
-
-				// If we get here, execve failed
-				// Remember we share the memory of our parent (vfork) so we need to exit using _exit() to avoid calling the parent exit handlers
-
-				PidOrErr err;
-				err.pid = -1;
-				err.err = errno;
-
-				pipe.Write(&err, sizeof(err));
-
-				_exit(1);
-			}
-			else if (grandChildPid != -1)
-			{
-				PidOrErr err;
-				err.pid = grandChildPid;
-
-				pipe.Write(&err, sizeof(err));
+				pipe.Write(&pid, sizeof(pid));
 
 				// Exits the child process, at this point the grand-child should have started
 				std::exit(0);
@@ -131,7 +117,7 @@ namespace Nz::PlatformImpl
 			::waitpid(childPid, &childStatus, 0);
 
 			PidOrErr pidOrErr;
-			if (pipe.Read(&pidOrErr, sizeof(pidOrErr) != sizeof(pidOrErr)))
+			if (pipe.Read(&pidOrErr, sizeof(pidOrErr)) != sizeof(pidOrErr))
 			{
 				// this should never happen
 				return Err("failed to create child: couldn't retrieve status from pipe");