C programming — evaluate this self-referential structure declaration for correctness.\n\nstruct emp\n{\n int ecode;\n struct emp e; / pointer to the same struct type (self-reference) */\n};\n\nIs there any language error in the declaration above?

Introduction / Context:
Self-referential structures are common in linked lists and trees. The question checks whether a struct can contain a pointer to its own type within its definition.

Given Data / Assumptions:

• The member e is declared as struct emp *.
• No storage is allocated yet; only the type layout is set.

Concept / Approach:
C permits a struct to contain pointers to its own (incomplete) type in the same declaration. What is not permitted is embedding an instance (by value) of the same struct inside itself, which would make the size infinite. Pointers are fixed-size and therefore allowed.

Step-by-Step Solution:

Verification / Alternative check:
This pattern underlies singly and doubly linked lists. Code that later allocates nodes and links e to other struct emp values compiles and runs normally.

Why Other Options Are Wrong:

• Structure declaration error: Incorrect; this is the idiomatic style.
• Linker error: There is no external symbol involved here.
• Undefined behavior: Only occurs if you dereference an uninitialized pointer at runtime, not from the declaration itself.

Common Pitfalls:
Confusing self-referential pointers (valid) with embedding the struct by value (invalid).

Final Answer:
No error