Merge pull request #742 from Rinzwind/tty-spawn

Add library with function to spawn a process connected to a pseudo-terminal

CMakeLists.txt

@@ -570,6 +570,10 @@ add_subdirectory(ffiTestLibrary ${CMAKE_CURRENT_BINARY_DIR}/build/ffiTestLibrary
 # Handling Third party dependencies
 add_third_party_dependencies_per_platform()
 
+if (UNIX)
+    addIndependentLibraryWithRPATH(tty ${CMAKE_CURRENT_SOURCE_DIR}/tty/tty.c)
+endif()
+
 # Signing Setup
 include(cmake/sign.cmake)
 

tty/tty.c

@@ -0,0 +1,71 @@
+#ifndef _XOPEN_SOURCE
+#define _XOPEN_SOURCE 700
+#endif
+
+#include <errno.h>
+#include <string.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <sys/ioctl.h>
+
+#define STATUS_ERROR 127
+#define CHECK_NULL(exp) \
+    if ((exp) == NULL) { \
+        _exit(STATUS_ERROR); \
+    }
+#define CHECK_ERROR(exp) \
+    if ((exp) == -1) { \
+        _exit(STATUS_ERROR); \
+    }
+#define CHECK_ERROR_PRINT(exp) \
+    if ((exp) == -1) { \
+        dprintf(2, "Error in %s at %s: %s\n", __func__, #exp, strerror(errno)); \
+        _exit(STATUS_ERROR); \
+    }
+
+pid_t tty_spawn(int fdm, const char *path, char *const argv[], char *const envp[])
+    /*
+        Spawns a process as a session leader with a pseudo-terminal as
+        its controlling terminal, its standard file descriptors
+        referring to the terminal, and executing a file with the given
+        arguments and environment. The first argument is expected to
+        be a file descriptor referring to a master pseudo-terminal
+        device as returned by 'posix_openpt'. The next three arguments
+        should be given as expected by 'execve'. The process ID of the
+        new process is returned, or -1 if one could not be created. If
+        the process is created but fails to open the slave device, or
+        set up the standard file descriptors, it exits with status 127.
+        If it fails to create the session, set the controlling
+        terminal or execute the file, it exits with status 127 after
+        printing an error message on the terminal that indicates the
+        call that failed.
+        
+        Provided through a library included with the VM to support
+        Pharo terminal emulators: it can only be partially replicated
+        through the FFI by using 'posix_spawn', as that seems to lack
+        a way to set the controlling terminal of the new process.
+    */
+{
+    pid_t pid = fork();
+    if (pid == 0)
+    {
+        char *sname;
+        CHECK_NULL(sname = ptsname(fdm));
+        int fds;
+        CHECK_ERROR(fds = open(sname, O_RDWR));
+        CHECK_ERROR(close(fdm));
+        CHECK_ERROR(close(0));
+        CHECK_ERROR(close(1));
+        CHECK_ERROR(close(2));
+        CHECK_ERROR(dup(fds));
+        CHECK_ERROR(dup(fds));
+        CHECK_ERROR(dup(fds));
+        CHECK_ERROR(close(fds));
+        CHECK_ERROR_PRINT(setsid());
+        CHECK_ERROR_PRINT(ioctl(0, TIOCSCTTY, 0));
+        CHECK_ERROR_PRINT(execve(path, argv, envp));
+    }
+    return pid;
+}