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Comment by Agraillo

1 day ago

Very interesting also as a thought-provoking idea. For example

  - It would be less challenging if function pointers variables are used instead of function. In this case, the code appended later may override the function variables it needs to fix/change

  - Since all the code is there, it is possible to invent some convention to compile/run previous versions without CVS machinery

11 comments

Agraillo

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kragen  1 day ago

I'm not sure how you would override the function pointers repeatedly without getting a compile error. Maybe you could instead use functions with GCC's weak attribute?

  • Y_Y  1 day ago

    I guess they mean to overwrite the pointers:

      void (*foo)(void)
  int main(){
    *foo();
  }
  void foo1(){...}
  foo = &foo1; // will be overwritten later
  void foo2(){...}
  foo = &foo2;

    I'm on my phone so I haven't compiled it, but that's the rough idea I got, define lots of versions and then set the version to the latest one.

    (You can skip the address-of for functions by punning, but reading the types is hard enough already.)

    • kragen  1 day ago

      That's not valid C; you can't put statements outside of functions, not even assignment statements or other expression statements. No C compiler I've ever used will accept it. Where would the compiled version of those statements go, in an init function? Linkers added support for those for C++ static initializers, where execution order isn't defined; C doesn't have anything similar. Are you expecting the compiler to execute the assignment statements at compile time, with a C interpreter?

      6 replies →

  • Agraillo  1 day ago

    I see no issue in setting it dynamically from the code, supposed to be set during start-up code. A global variable representing a function pointer and this variable either changed several times (if the latest addition allows execution of previous routines then setting its new value) or just once for the latest version if the logic somehow disables previous start-up routines. Can be called "dynamic inheritance"