Am 11.08.23 um 20:24 schrieb Jeff King: > On Fri, Aug 11, 2023 at 07:59:12PM +0200, René Scharfe wrote: > >>> we are defining an inline function with the explicit goal of passing it >>> as a function pointer. I don't remember all of the standard's rules >>> here. Are we guaranteed that it will create a linkable version if >>> necessary? >> >> I don't see on which basis the compiler could refuse. We can't expect >> the function address to be the same across compilation units, but we >> don't need that. If there's a compiler that won't do it or a standards >> verse that makes this dubious then I'd like to know very much. > > I seem to recall some quirks where an inline function that is not called > directly is not required to be compiled at all, and the compiler can > assume that there is a definition available in another translation unit. C99 says in 6.7.4 Function specifiers: "It is unspecified whether a call to the function uses the inline definition or the external definition.", referring to functions with both types of definition. So a compiler could ignore the inline version for those. > But I think that only applies when no storage-class specifier is > provided. In this case, you said "static", so I think it's OK? That's how I understand it as well -- there is no external version to choose and the compiler is not free to ignore the inline one. > It's possible I'm mis-remembering the issues, too. One problem is that > pre-C99, you might end up with the opposite problem (a compiled function > with visible linkage that conflicts with other translation units at link > time). E.g. here: > > https://stackoverflow.com/questions/51533082/clarification-over-internal-linkage-of-inline-functions-in-c/51533367#51533367 > > But I think with "static" we should always be OK. *nod* > Don't get me wrong, I like type checking. It's just that doing weird > things with the language and pre-processor also carries a cost, > especially in an open source project where new folks may show up and say > "what the hell is this macro doing?". That's a friction for new > developers, even if they're comfortable with idiomatic C. Sure, but that ship has sailed in this specific case. Standard option parsing would use getopt or getopt_long, neither of which has void pointers. We already carry the cost of our OPT_ macros. Let's ease it. > That said... > >> A good example in parseopt: The patch below adds type checking to the >> int options and yields 79 warning about incompatible pointers, because >> enum pointers were used in integer option definitions. The storage size >> of enums depends on the member values and the compiler; an enum could be >> char-sized. When we access such a thing with an int pointer we write up >> to seven bytes of garbage ... somewhere. We better fix that. > > ...I do find this evidence compelling. It's 3 instead of 7 bytes of garbage, but the point still stands.. René
