Assign one struct to another in C

Yes if the structure is of the same type. Think it as a memory copy.

Yes, assignment is supported for structs. However, there are problems:

struct S {   char * p;};struct S s1, s2;s1.p = malloc(100);s2 = s1;

Now the pointers of both structs point to the same block of memory - the compiler does not copy the pointed to data. It is now difficult to know which struct instance owns the data. This is why C++ invented the concept of user-definable assignment operators - you can write specific code to handle this case.

First Look at this example :

The C code for a simple C program is given below

struct Foo {    char a;    int b;    double c;} foo1, foo2;void foo_assign(void){    foo1 = foo2;}int main(/*char *argv[],int argc*/){    foo_assign();    return 0;}

The Equivalent ASM Code for foo_assign() is

00401050 <_foo_assign>:  401050:   55                      push   %ebp  401051:   89 e5                   mov    %esp,%ebp  401053:   a1 20 20 40 00          mov    0x402020,%eax  401058:   a3 30 20 40 00          mov    %eax,0x402030  40105d:   a1 24 20 40 00          mov    0x402024,%eax  401062:   a3 34 20 40 00          mov    %eax,0x402034  401067:   a1 28 20 40 00          mov    0x402028,%eax  40106c:   a3 38 20 40 00          mov    %eax,0x402038  401071:   a1 2c 20 40 00          mov    0x40202c,%eax  401076:   a3 3c 20 40 00          mov    %eax,0x40203c  40107b:   5d                      pop    %ebp  40107c:   c3                      ret    

As you can see that a assignment is simply replaced by a "mov" instruction in assembly, the assignment operator simply means moving data from one memory location to another memory location.The assignment will only do it for immediate members of a structures and will fail to copy when you have Complex datatypes in a structure. Here COMPLEX means that you cant have array of pointers ,pointing to lists.

An array of characters within a structure will itself not work on most compilers, this is because assignment will simply try to copy without even looking at the datatype to be of complex type.