Is there a guarantee that a cast of a pointer does not change its representation and size?   -----Ursprüngliche Nachricht----- Von:Gašper Ažman via Std-Proposals <std-proposals_at_[hidden]> Gesendet:Mo 27.01.2025 02:34 Betreff:Re: [std-proposals] Make all data pointers intercompatible An:std-proposals_at_[hidden]; CC:Gašper Ažman <gasper.azman_at_[hidden]>; You know all pointers are the same size because they're all static_cast-able to void* and back. On Mon, Jan 27, 2025 at 9:12 AM Jeremy Rifkin via Std-Proposals <std-proposals_at_[hidden] <mailto:std-proposals_at_[hidden]> > wrote: > It's possible if the compiler hides it from the programmer. For instance if CHAR_BIT==8, and if the CPU instructions deal with 16-Bit operands, then you can have: > >    CHAR_BIT == 8 >    sizeof(int*) == 2 >    sizeof(char*) == 3  All the language cares about is that you can in fact address every byte of memory. From a language perspective, if CHAR_BIT == 8 then the smallest addressable unit of memory is 8 bits irrespective of hardware details.  Between https://eel.is/c++draft/basic.memobj#intro.memory-1 and https://eel.is/c++draft/basic.compound#7 and the fact struct Frog; Frog* ptr1 = nullptr; Frog* foo(); Frog* ptr2 = foo(); has to work I think it's sufficiently covered by the standard that all pointers to non-fundamental objects are the same size (or at least compatible in some way to make everything here work). Even if you had a system where sizeof(char*) == 3 and sizeof(int*) == 2 you would know sizeof(void*) >= 3.  Cheers, Jeremy   On Sun, Jan 26, 2025 at 5:42 PM Frederick Virchanza Gotham via Std-Proposals <std-proposals_at_[hidden] <mailto:std-proposals_at_[hidden]> > wrote: On Sun, Jan 26, 2025 at 11:17 PM Jeremy Rifkin wrote: > > > For example on a system where CHAR_BIT==8 but the smallest addressable unit of memory is 16 bits > > That's not possible https://eel.is/c++draft/basic.memobj#intro.memory-1 It's possible if the compiler hides it from the programmer. For instance if CHAR_BIT==8, and if the CPU instructions deal with 16-Bit operands, then you can have:     CHAR_BIT == 8     sizeof(int*) == 2     sizeof(char*) == 3 An int* is a 16-Bit number representing a memory address. A char* is a 16-Bit number representing a memory address, with an extra byte to indicate the offset. -- Std-Proposals mailing list Std-Proposals_at_[hidden] <mailto:Std-Proposals_at_[hidden]> https://lists.isocpp.org/mailman/listinfo.cgi/std-proposals -- Std-Proposals mailing list Std-Proposals_at_[hidden] <mailto:Std-Proposals_at_[hidden]> https://lists.isocpp.org/mailman/listinfo.cgi/std-proposals -- Std-Proposals mailing list Std-Proposals_at_[hidden] https://lists.isocpp.org/mailman/listinfo.cgi/std-proposals