5 ms·

I don't think I've ever thought of explicitly calling main(). Made me chuckle.

• akdev1l 2y ago
  I think it is UB Edit: actually looks like it is UB in C++ but not C
  • colejohnson66 2y ago
    Why would calling main be UB!? How is crt0 supposed to work?
    • tomjakubowski 2y ago
      crt0 generally isn't C and isn't subject to C's rules
      • astrange 2y ago
        malloc() can't be implemented in C either because it's defined as doing things (creating new memory objects) there are no lower level mechanisms in C to do.
        • eacnamn 2y ago
          all malloc is defined to do is to return a pointer to storage of appropriate size and alignment, which can easily be done in pure standard C by defining a static array and chopping it up as needed. that's not a brilliant way of doing that, but achievable without leaving standard C
          • astrange 2y ago
            > The malloc function allocates space for an object whose size is specified by size and whose value is indeterminate. > The lifetime of an allocated object extends from the allocation until the deallocation. Each such allocation shall yield a pointer to an object disjoint from any other object. A static array is "an object" already. A pointer to the middle of it is not a new object.
          • gpderetta 2y ago
            AFAIK that can break because of the strict aliasing rules (although it might work in practice). Even if char can alias anything, the reverse is not true and you can't legally store other types in a static array of char type. You should be able to use anonymous memory though, so for example if you get your storeag via mmap or some other allocator it should be fine.
            • astrange 2y ago
              There isn't anything called mmap in the C standard. That's what I mean by it not being possible to implement in standard C. It is possible in some implementations of C.
    • akdev1l 2y ago
      As the other person pointed out, anything that happens before main is strictly not covered by the C standard. Even things like “printf” can’t be implemented purely in standard C. Even making a syscall is outside of the scope of the C standard.