snprintb
int snprintb(char *buf, size_t buflen, const char *bitfmt, uint64_t val);
snprintb(buf, sizeof(buf), MACH_CONF_FLAGS, cap.arch.mach_conf_support);
snprintb(buf, sizeof(buf), VCPU_CONF_FLAGS, cap.arch.vcpu_conf_support);
snprintb(buf, sizeof(buf), XCR0_FLAGS1, cap.arch.xcr0_mask);