> Hi all,
 >
 > Another episode in the ongoing "Peter learns something new about C" =20=
 
 > drama. John came to office hours today and we hacked a rough =20
 > implementation of SDBM together. As part of that, we had "move =20
 > around" these kinds of structures:
 >
 >   struct entry {
 >     char key[MAX_KEY_LENGTH];
 >     char value[MAX_VALUE_LENGTH];
 >   };
 >
 > Remember how in C you cannot assign arrays? So if we have                                                                                                                                                                 
 >                                                                                                                                                                                                                                  
 >   int a[10];
 >   int b[10];
 >
 > we *cannot* write an assignment like
 >
 >   a =3D b;
 >
 > since the compiler will complain about the types not matching up. =20
 > We can, however, assign structures. So if we have
 >
 >   struct point {
 >     int x;
 >     int y;
 >   } a, b;
 >
 > we *can* write
 >
 >   a =3D b;
 >
 > and what will happen is that the components of the structure get =20
 > assigned. Now imagine my surprise when it comes to the struct entry =20=
 
 > defined above. If you have
 >
 >   struct entry a;
 >   struct entry b;
 >
 > you *can* write
 >
 >   a =3D b;
 >
 > even though the elements of the structure are themselves arrays. =20
 > Fascinating! Why? Well, since assignments between arrays are not =20
 > allowed, you cannot explain assignment between structs by =20
 > assignment of their fields alone! In a saner language the same =20
 > rules would apply to all arrays, whether they are part of a struct =20
 > or not. But in C that's apparently not the case.
 >
 > So far I've been unable to find a good explanation for this =20
 > behavior. In fact, it's *so* inconsistent that it never even =20
 > crossed my mind to try it before John asked "Why don't we just =20
 > assign the structs instead of using two different strcpy() calls?" =20
 > in office hours today. If anyone here finds a good explanation, =20
 > please do share. :-)
 >
 > Cheers,
 > Peter
 >
 > PS: And by "good explanation" I don't mean "well the C compiler =20
 > does a memcpy() for structs without even looking at the components" =20=
 
 > since that's just an implementation choice but not essential to the =20=
 
 > language.