On Mon, 27 Dec 2021 15:18:38 -0600, Joe Nelson wrote: > I recently discovered the funopen function, and was confused by its > declaration. Specifically, one of its arguments is > > fpos_t (*seekfn)(void *, fpos_t, int) > > I wondered how seekfn would be able to return an error code, since the > C99 standard section 7.19.1 specifies fpos_t as an opaque type, not one > the user can construct. Only after some research did I learn that fpos_t > is actually a typedef for off_t on OpenBSD.
You are correct, fpos_t is not guaranteed to be an integral type. For instance, it may be struct on some systems. > I propose we change the declaration to take this argument instead: > > off_t (*seekfn)(void *, off_t, int) > > This shouldn't cause any backward incompatibility, right, because > they're in fact the same type? Using off_t clearly communicates that > we're dealing with a signed integer type. > > FWIW, NetBSD uses off_t. https://man.netbsd.org/funopen.3 That seems like the best approach. FWIW, funopen() emulation in the Linux libbsd uses off_t for the same reason. - todd
