Philipp Hortmann <philipp.g.hortmann@xxxxxxxxx> writes: > I do like this example: > https://lwn.net/Articles/745261/ > > ... > pr_err("%llx%llx\n", (u64) (val >> 64), (u64) val); > pr_err("%llx%llx\n", (u64) (v >> 64), (u64) v); > ... > This will produce the wrong output unless at least one of bit 60 - 63 is set and have a confusing leading zero unless one of the upper 64 bits is set. Running this test: #include <stdio.h> #include <stdlib.h> int main(int argc, char **argv) { __uint128_t foo; if (argc < 3) return -1; foo = (__uint128_t)strtoull(argv[1], NULL, 0) << 64 | strtoull(argv[2], NULL, 0); fprintf(stderr, "foo=0x%llx%llx\n", (__uint64_t) (foo >> 64), (__uint64_t) foo); fprintf(stderr, "foo=0x%016llx%016llx\n", (__uint64_t) (foo >> 64), (__uint64_t) foo); return 0; } Produces: bjorn@miraculix:~$ /tmp/x 1 0 foo=0x10 foo=0x00000000000000010000000000000000 bjorn@miraculix:~$ /tmp/x 1 2 foo=0x12 foo=0x00000000000000010000000000000002 bjorn@miraculix:~$ /tmp/x 0 2 foo=0x02 foo=0x00000000000000000000000000000002 Bjørn _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
