Extra bytes when declaring a member of a struct as uint32_t

Question

I have a problem when using the uint32_t type from the stdint.h library. If I run the following code (on Ubuntu linux 11.10 x86_64, g++ version 4.6.1):

#include          


        

Answer 1

You need to declare to the compiler to pack the structure

I believe that this will work for GCC

struct test
    {
            unsigned char  field1;
            unsigned short field2;
            unsigned long  field3;
    } __attribute__((__packed__));

In MS it would be something using the pragma packed

http://www.cplusplus.com/forum/general/14659/

#pragma pack(push, 1) // exact fit - no padding
struct MyStruct
{
  char b; 
  int a; 
  int array[2];
};
#pragma pack(pop) //back to whatever the previous packing mode was