* Iain Sandoe: > In the case that a call is built and no prototype is available, the > assumption is that all parms are named. The promotion is then done > according to the C promotion rules. > > [for the number of args that can be passed in int regs] the callee > will happen to observe the same rules in this case. > > It will, however, break once we overflow the number of int regs.. :/
Exactly. > The case that is fundamentally broken from scratch is of a variadic function > called without a prototype - since the aarch64-darwin ABI places unnamed > parms differently. That part is true for powerpc64le as well, due to the caller-provided saved parameter area which only exists with variadic calls. This already happens in very simple cases, like the POSIX open function. The corruption is quite difficult to diagnose, too. 8-( But it's also quite rare to see such bugs. > Given we have 8 int regs available, probably many calls will work .. Oh, I didn't know that so many registers were available. Maybe that's enough to paper over the lack of ABI compatibility for now. Presumably you could count the number of arguments and emit a warning at least? C++ metaprogramming involving many parameters tends to use variadic templates of non-variadic functions, so that shouldn't be a problem. Thanks, Florian
