On Sat, 18 Aug 2018 at 02:22, Vincent Lefevre <vincent+gcc@xxxxxxxxxx> wrote: > > On 2018-08-18 00:14:50 +0100, Jonathan Wakely wrote: > > On Fri, 17 Aug 2018 at 23:27, Vincent Lefevre wrote: > > > > > > What's the point of the pointer-to-int-cast warning, which is > > > enabled by -Wall? > > > > > > I get this warning under 32-bit Linux when casting a pointer to > > > uintmax_t. I use uintmax_t to make sure that the integer size is > > > large enough. So, what's the problem? > > > > sizeof(uintmax_t) != sizeof(void*). > > But why would this make the conversion invalid? The warning doesn't say it's invalid, it says they're different sizes. I don't know why casting to an integer type that's larger than a pointer is considered a problem (obviously the other way around is bad), but you can use -Wno-pointer-to-int-cast if you don't care about that. > > Why not use uintptr_t instead? > > Because this is not portable: "These types are optional." > > Another reason is that the code needs to support C90 compilers > (and if uintmax_t is not available, there is a fallback to > unsigned long long, else unsigned long). So you could try uintptr_t first and if that's not available, try uintmax_t, then the other fallbacks.
