On Sat, 8 Jan 2022 11:30:41 +0100, Jakub Wilk <jwilk@xxxxxxxxx> wrote: > For the record, this is what you get when you compile the original code > on a 64-bit architecture: > > $ gcc -Wall -pthread malloc_info-example.c > malloc_info-example.c: In function 'thread_func': > malloc_info-example.c:16:14: warning: cast from pointer to integer of > different size [-Wpointer-to-int-cast] 16 | int tn = (int) arg; > | ^ > malloc_info-example.c: In function 'main': > malloc_info-example.c:57:32: warning: cast to pointer from integer of > different size [-Wint-to-pointer-cast] 57 | > (void *) tn); | ^ > > * Alejandro Colomar <alx.manpages@xxxxxxxxx>, 2022-01-08, 03:25: > >On 1/7/22 17:46, Stephen Kitt wrote: > >>int isn't large enough to store pointers on all platforms, use > >>intptr_t instead. > > > >Well, since the pointer came from a previous 'int', there should be no > >problem. But since the C language (or even POSIX) is very permissive > >about what a conforming implementation can do with pointers, and it > >only guarantees conversions to/from [u]intptr_t, I'd take this patch > >for correctness. However... > > The standards guarantee that void* → intptr_t → void* round-trips, > but that's not what this code does. > > The example converts int → void* → int. Changing int to intptr_t makes > the compiler warnings go away, but I don't think it improves correctness > in any way. Agreed, the example is just trying to pass an int into the function given to pthread_create. AFAICT the only requirement for correctness is that the type used is at most the size of void *. It’s probably not worth bothering about the compiler warning... Regards, Stephen
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