ubuntu@ubuntu:~$ ./a.out
endianess: little
try to access unaligned word
equal to 0x1234: YES
value: 0x1234
done
On Wed, Jul 29, 2015 at 3:55 PM, Dennis Luehring <dl.so...@gmx.net> wrote:
> Am 29.07.2015 um 14:34 schrieb Karel Gardas:
>>
>> Once it boots, tell me how to find the asnwers to your
>> questions.
>
>
> compile with gcc test.cpp and run
>
> -----------
> #include <stdint.h>
> #include <stdio.h>
> #include <stddef.h>
> #include <string.h>
> #include <assert.h>
>
> int main()
> {
> uint16_t value = 0x1234;
>
> {
> volatile uint8_t* ptr = (uint8_t*)&value;
> printf("endianess: %s\n", ptr[0]==0x34 ? "little":"big");
> }
>
> uint8_t buffer[1+sizeof(value)]={0};
> uint8_t* ptr = buffer;
> if(ptrdiff_t(ptr) % 2 == 0)
> {
> ++ptr;
> }
> uint16_t* unaligned_word = (uint16_t*)ptr;
>
> ::memcpy(unaligned_word, &value, sizeof(value));
>
> printf("try to access unaligned word\n");
> uint16_t read = *unaligned_word; // here can happen Bus-Errors,
> Exceptions, whatever your architecture likes
> printf(" equal to 0x%04X: %s\n", value, read == value ? "YES":"!!NO!!");
> // sometimes you get the value - but its still wrong
> printf(" value: 0x%04X\n", read);
> printf("done\n");
>
> return 0;
> }
> -----------
>
