c - Why can I still access a member of a struct after the pointer to it is freed? -

if define structure...

struct linknode {   int node_val;   struct linknode *next_node; }; 

and create pointer it...

struct linknode *mynode = malloc(sizeof(struct linknode)); 

...and free() it...

free(mynode); 

...i can still access 'next_node' member of structure.

mynode->next_node 

my question this: which piece of underlying mechanics keeps track of fact block of memory supposed represent struct linknode? i'm newbie c, , expected after used free() on pointer linknode, no longer able access members of struct. expected sort of 'no longer available' warning.

i love know more how underlying process works.

the compiled program no longer has knowledge struct linkednode or field named next_node, or that. names gone compiled program. compiled program operates in terms of numerical values, can play roles of memory addresses, offsets, indices , on.

in example, when read mynode->next_node in source code of program, compiled machine code reads 4-byte numerical value reserved memory location (known variable mynode in source code), adds 4 (which offset of next_node field) , reads 4-byte value @ resultant address (which mynode->next_node). code, can see, operates in terms of integer values - addresses, sizes , offsets. not care names, linkednode or next_node. not care whether memory allocated and/or freed. not care whether of these accesses legal or not.

(the constant 4 repeatedly use in above example specific 32-bit platforms. on 64-bit platforms replaced 8 in (or all) instances.)

if attempt made read memory has been freed, these accesses might crash program. or might not. matter of pure luck. far language concerned, behavior undefined.