C program diagnosis: modifying a const union and printing its members #include #include #include union employee { char name[15]; int age; float salary; }; const union employee e1; int main() { strcpy(e1.name, "K"); printf("%s", e1.name); e1.age = 85; printf("%d", e1.age); printf("%f", e1.salary); return 0; }

Introduction / Context:This item tests const-correctness with aggregates. The union instance e1 is declared const, yet the code attempts to modify its members via strcpy and direct assignment.

Given Data / Assumptions:

• union employee e1 is qualified with const.
• Operations attempt to write into e1.name and e1.age.
• strcpy requires a writable destination.

Concept / Approach:In C, const at the object level forbids any modification through that object. Accessing a member of a const union yields a const-qualified lvalue for that member. Therefore, both strcpy(e1.name, ...) and e1.age = 85 violate const-correctness.

Step-by-Step Solution:Declaration: const union employee e1; → all member writes are forbidden.strcpy(e1.name, "K"); → attempts to write into a const char array → constraint violation.e1.age = 85; → attempts to write into const int → also a violation.Even reading different members of a union is fine, but writing is disallowed due to const.

Verification / Alternative check:Remove const (union employee e1;) or use a non-const temporary. Also add #include to avoid implicit declaration (modern compilers).

Why Other Options Are Wrong:“RValue/LValue required” do not describe the fundamental issue. “No error” is false; compilers diagnose attempts to modify const objects.

Common Pitfalls:Assuming const applies only to the union itself but not its members; forgetting to include string.h; misunderstanding that union type does not change const semantics.

Final Answer:Error: cannot modify const object