Wednesday, June 6, 2012

Format string for printk with different types of variables in C

int %d or %x
unsigned int %u or %x
long %ld ot %lx
unsigned long %lu or %lx
long long %lld or %llx
unsigned long long %llu or %llx
size_t %zu or %zx
ssize_t %zd or %zx

Raw pointer value SHOULD be printed with %p.

u64 SHOULD be printed with %llu/%llx, (unsigned long long):

printk("%llu", (unsigned long long)u64_var);

s64 SHOULD be printed with %lld/%llx, (long long):

printk("%lld", (long long)s64_var);

If type is dependent on config option (sector_t), use format specifier
of biggest type and explicitly cast to it.

Reminder: sizeof() result is of type size_t.