check_zero
check_zero(&zero);
int check_zero, const char *buf, size_t len)
if (check_zero && !x)
#define TUNE_ATTR(name, check_zero) \
return tune_set(sdp, &sdp->sd_tune.gt_##name, check_zero, buf, len); \
check_zero(msb, SYS_READ);
check_zero(msb, SYS_WRITE);
check_zero(msb, X64_READV);
check_zero(msb, X64_WRITEV);
check_zero(msb, SYS_READ | X32_BIT);
check_zero(msb, SYS_WRITE | X32_BIT);
check_zero(msb, X32_READV | X32_BIT);
check_zero(msb, X32_WRITEV | X32_BIT);