Attempting to write into a const union member: Given const union employee e1; and strcpy(e1.name, "K");, what is the compilation result?

Introduction / Context:Declaring an object as const in C makes the entire object read-only. For aggregates such as structs and unions, each member becomes non-modifiable through that object. Attempting to write into a member via functions like strcpy therefore violates const-correctness and must be diagnosed by the compiler. This question highlights how const applies transitively to members of a union and how that affects typical string-copy operations.

Given Data / Assumptions:

• union employee { char name[15]; int age; float salary; };
• const union employee e1; declares a read-only union object.
• strcpy(e1.name, "K"); attempts to modify a member array.

Concept / Approach:

• Because e1 is const, its member name is a non-modifiable lvalue. Passing it to strcpy (which expects a char * destination) is illegal: the expression has type const char * after array-to-pointer decay.
• Compilers typically emit diagnostics such as 'assignment of read-only location' or 'lvalue required' for the attempted write.
• Even if forced via casts, modifying a const object produces undefined behavior.

Step-by-Step Solution:

Verification / Alternative check:

Why Other Options Are Wrong:

• RValue required: the issue is not rvalue vs lvalue, but non-modifiable lvalue.
• Type-conversion message about int pointers: unrelated to this code.
• No error/Runtime crash only: incorrect; this is a compile-time const violation.

Common Pitfalls:

• Casting away const to appease strcpy; writing through such a cast is undefined behavior.
• Assuming const applies only to scalars; it applies to aggregates as well.

Final Answer: