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Spawning a process by passing state explicitly is what Windows does. The CreateProcess call takes 10 parameters, several of which are structures containing eve

Spawning a process by passing state explicitly is what Windows does. The CreateProcess call takes 10 parameters, several of which are structures containing even more parameters - http://msdn.microsoft.com/en-us/library/windows/desktop/ms682425(v=vs.85).aspx http://msdn.microsoft.com/en-us/library/windows/desktop/ms68... I do like that fork, then setup functions, then exec keeps the code simpler. If everything is done as a single call like CreateProcess then it needs to have a way of passing what the setup functions need as data - rather a lot of it.

dpark 12y ago
That's conflating separate issues. Windows could have a CreateProcessSimple() call that spawns a new process without so many options. CreateProcess is complex not so much because it is one call instead of two, but because it has all options jumbled together. Meanwhile the Linux/Unix decision was to have about a dozen different APIs to do variants of the same thing (fork, vfork, and clone plus execl, execlp, execle, execv, execvp, execvpe, fexecve, posix_spawn, posix_spawnp, and probably more). This isn't really any less complex. The argument complexity of CreateProcess could not possibly derive from merging fork() and exec() because fork() has no arguments.
- caf 12y ago
  It's not enough to merge fork() and execve(), because what actually happens is some variant of: fork(); open(); close(); dup2(); fdcntl(); sigprocmask(); sigaction(); setrlimit(); prctl(); chdir(); chroot(); capset(); execve(); (and perhaps more besides, with new ones potentially added with new features, for example seccomp();)
  - dpark 12y ago
    That seems like compelling evidence that the Linux method is more complex than the Windows method (or at least no less complex). Calling a bunch of complex functions is not simpler than setting up a bunch of complex params and then calling one function.
    - caf 12y ago
      Approximately zero programs will call all of those functions, but each will call its own required subset of them. If you don't care about running the child with an altered root directory, you don't need to call chroot().
      - dpark 12y ago
        Of course. Most programs also don't need all the esoteric options that can be passed into CreateProcess either.
        caf 12y ago
        I don't think anyone who's thought about it for a moment disagrees that starting a process has a large degree of potential complexity, regardless of the operating system. The question is whether it's better (more elegant) to load that complexity onto one complex function call, or farm it out to multiple simple function calls. It is apparent that this is a question in which personal taste is involved.
- ridiculous_fish 12y ago
  CreateProcess is complex because spawning a new process is essentially complex. The brilliance of fork/exec is in the realization that the tasks you do during process creation are the same as the tasks you do during normal execution, and therefore you can just re-use those functions. For example, CreateProcess has a parameter for the current directory; fork/exec doesn't need one because you just use chdir on the child side of fork. The proliferation of exec* is indeed baffling, but these are just dumb variants trying to make the exec call itself "easier." They don't reflect any essential complexity.

dpark 12y ago

That's conflating separate issues. Windows could have a CreateProcessSimple() call that spawns a new process without so many options. CreateProcess is complex not so much because it is one call instead of two, but because it has all options jumbled together. Meanwhile the Linux/Unix decision was to have about a dozen different APIs to do variants of the same thing (fork, vfork, and clone plus execl, execlp, execle, execv, execvp, execvpe, fexecve, posix_spawn, posix_spawnp, and probably more). This isn't really any less complex. The argument complexity of CreateProcess could not possibly derive from merging fork() and exec() because fork() has no arguments.

caf 12y ago
It's not enough to merge fork() and execve(), because what actually happens is some variant of: fork(); open(); close(); dup2(); fdcntl(); sigprocmask(); sigaction(); setrlimit(); prctl(); chdir(); chroot(); capset(); execve(); (and perhaps more besides, with new ones potentially added with new features, for example seccomp();)
- dpark 12y ago
  That seems like compelling evidence that the Linux method is more complex than the Windows method (or at least no less complex). Calling a bunch of complex functions is not simpler than setting up a bunch of complex params and then calling one function.
  - caf 12y ago
    Approximately zero programs will call all of those functions, but each will call its own required subset of them. If you don't care about running the child with an altered root directory, you don't need to call chroot().
    - dpark 12y ago
      Of course. Most programs also don't need all the esoteric options that can be passed into CreateProcess either.
      - caf 12y ago
        I don't think anyone who's thought about it for a moment disagrees that starting a process has a large degree of potential complexity, regardless of the operating system. The question is whether it's better (more elegant) to load that complexity onto one complex function call, or farm it out to multiple simple function calls. It is apparent that this is a question in which personal taste is involved.
ridiculous_fish 12y ago
CreateProcess is complex because spawning a new process is essentially complex. The brilliance of fork/exec is in the realization that the tasks you do during process creation are the same as the tasks you do during normal execution, and therefore you can just re-use those functions. For example, CreateProcess has a parameter for the current directory; fork/exec doesn't need one because you just use chdir on the child side of fork. The proliferation of exec* is indeed baffling, but these are just dumb variants trying to make the exec call itself "easier." They don't reflect any essential complexity.