In C programming (stdarg.h), what does the macro va_arg do when iterating through a variable argument list? Clarify whether it both extracts the current argument value of the specified promoted type and advances the internal va_list position to the next argument.

Introduction / Context:
Functions that accept a variable number of arguments (variadic functions) in C use facilities from stdarg.h: va_list, va_start, va_arg, and va_end. A common point of confusion is the exact role of va_arg in stepping through the unnamed arguments. This item checks whether you understand that va_arg both fetches the current argument and moves the internal pointer forward to the next one.

Given Data / Assumptions:

• The function is declared with at least one fixed (named) parameter followed by an ellipsis ... .
• A va_list object has been initialized with va_start using the last fixed parameter.
• Each variadic argument undergoes default argument promotions (e.g., float → double, types smaller than int → int).

Concept / Approach:
After va_start initializes traversal, va_arg(list, type) is invoked repeatedly. For each call, C expects you to pass the promoted type that matches how the caller provided the argument. va_arg returns the value of the current argument and then advances the internal position in the va_list to point to the next argument. When you finish, you must call va_end to allow the implementation to clean up.

Step-by-Step Solution:
Declare va_list ap; then call va_start(ap, last_named_param).Call v1 = va_arg(ap, int); // extracts current promoted int and advances.Call v2 = va_arg(ap, double); // extracts next promoted double and advances again.After all arguments are consumed, call va_end(ap).

Verification / Alternative check:
Examine a typical printf-like loop that reads arguments until a format string is exhausted. Each va_arg corresponds to one conversion and automatically steps to the next parameter. If va_arg did not advance, the loop would return the same value repeatedly and never progress.

Why Other Options Are Wrong:
“Incorrect” ignores the specification that va_arg advances. “Only for the first variadic argument” is wrong because va_arg is used for each argument. “Works only with stdio.h” confuses library layers; stdarg.h is independent. “Not applicable in C” is false because stdarg.h is a core C feature.

Common Pitfalls:
Using the wrong type with va_arg (mismatch with promotions), forgetting va_end, or assuming va_arg peeks without advancing.

Final Answer:
Correct