size of struct in C
c, struct, structure-packing
Solution
The compiler may add padding for alignment requirements. Note that this applies not only to padding between the fields of a struct, but also may apply to the end of the struct (so that arrays of the structure type will have each element properly aligned).
For example:
struct foo_t {
int x;
char c;
};
Even though the `c` field doesn't need padding, the struct will generally have a `sizeof(struct foo_t) == 8` (on a 32-bit system - rather a system with a 32-bit `int` type) because there will need to be 3 bytes of padding after the `c` field.
Note that the padding might not be required by the system (like x86 or Cortex M3) but compilers might still add it for performance reasons.
Problem
Possible Duplicate: Why isn’t sizeof for a struct equal to the sum of sizeof of each member? Consider the following C code: ``` #include <stdio.h> struct employee { int id; char name[30]; }; int main() { struct employee e1; printf("%d %d %d", sizeof(e1.id), sizeof(e1.name), sizeof(e1)); return(0); } ``` The output is: 4 30 36 Why is the size of the structure not equal to the sum of the sizes of its individual component variables?