On Sun, Feb 11, 2018 at 7:30 PM, Werner LEMBERG <w...@gnu.org> wrote: > >>> (void*)(size_t)(x) should be safe, c90, and warning-less. >> >> You assume that all machines have a flat, linear memory model.... ;-( >> >> The "safe", portable way is to use >> >> (void *)(((char *)0) + (x)) >> >> to cast an integer to a void pointer, and use >> >> (ptrdiff_t)((char *)(x)) - ((char *)0) >> >> to cast a pointer to an integer. > > Interesting. Can you name an example of a machine with a non-linear > memory model?
24bit/32bit embedded CPU designs, typically designs predating the widespread adoption of 64bit address space&&pointers. For example i960 can implement one-address-space-per-object-type - for those who remember C64's "banking": Sort of One-bank-per-object-type. In such a scenario a pointer is only valid for the type it was used for since the same "integer" value can refer to a completely different chunk of memory for another object type. A more classical scenario is data&&code separation as in the https://en.wikipedia.org/wiki/Harvard_architecture That's why the wording in the ISO >= C89 standard has a bit more complex wording about pointer differences, but I can't quote them since my book (https://www.amazon.de/Annotated-ANSI-Standard-Programming-Languages-C/dp/0078819520/ref=sr_1_1) is a few 100km away right now... ---- Bye, Roland -- __ . . __ (o.\ \/ /.o) roland.ma...@nrubsig.org \__\/\/__/ MPEG specialist, C&&JAVA&&Sun&&Unix programmer /O /==\ O\ TEL +49 641 3992797 (;O/ \/ \O;) _______________________________________________ Freetype-devel mailing list Freetype-devel@nongnu.org https://lists.nongnu.org/mailman/listinfo/freetype-devel
