Sumit Kumar Jain writes: > I was going through the GLib 2.8.4 code and while reading the file > gspawn-win32.c I saw that a helper process is required in case of > windows, while no such process is requied for LINUX. I want to know > why is such a mechanism required. Basically, because Win32 doesn't have fork(). As the comment in gspawn-win32.c says: /* * Implementation details on Win32. * * - There is no way to set the no-inherit flag for * a "file descriptor" in the MS C runtime. The flag is there, * and the dospawn() function uses it, but unfortunately * this flag can only be set when opening the file. * - As there is no fork(), we cannot reliably change directory * before starting the child process. (There might be several threads * running, and the current directory is common for all threads.) * * Thus, we must in most cases use a helper program to handle closing * of (inherited) file descriptors and changing of directory. The * helper process is also needed if the standard input, standard * output, or standard error of the process to be run are supposed to * be redirected somewhere. * * The structure of the source code in this file is a mess, I know. */ If we used CreateProcess() directly instead of the C library spawn*() functions, the working directory could be set. But the handling the C file descriptor inheritance and argument vector serialization into a command line would require essentially duplicating much of the code in the C runtime. Sure, the C runtime sources are included with the MSVC compiler (and I have a legal license), and you can even find them on the net... But using knowledge gleaned from the C runtime source code would be of dubious legality. Microsoft can claim that the undocumented method they use to pass inherited C file descriptor -> Win32 file handle mapping is a trade secret. It's safer to just use the spawn*() functions. And, if we used CreateProcess() directly, the underlying Win32 file handles would be inherited anyway, even if the corresponding C file descriptors wouldn't be. When the helper process closes the inherited C file descriptors that shouldn't be inherited, the Win32 file handles get closed (in the helper process), too. --tml _______________________________________________ gtk-list@xxxxxxxxx http://mail.gnome.org/mailman/listinfo/gtk-list
