c - Is it possible to change the definition of structs at runtime? -

i don't know why ever want this, curious if knew answer. possible @ run time use 1 struct definition while, , later change definition?

i.e.

typedef struct {     int a;     int b; }my_struct; 

and later on...

typedef struct {     int a;     int b;     int c; }my_struct; 

no, can't change definition of given type, there's nothing wrong casting totally different type, assuming underlying data laid out , otherwise compatible.

for example, consider:

struct s_xyzzy {     int a;     int b; };  struct s_plugh {     int a;     char b0;     char b1;     char b2;     char b3; };  struct s_xyzzy *xyzzy = malloc (sizeof (*xyzzy)); ((struct s_plugh *)xyzzy)->b0 = 'x'; 

by casting xyzzy different compatible type, can access fields in different way.

keep in mind compatibility important , have know underlying memory correctly aligned between 2 structures.

you can placing both structures union, using overlapped memory.