In C variadic functions, must there be at least one fixed (named) parameter before the ellipsis so that va_start() can be given a valid last named argument?

Introduction / Context:
va_start requires the name of the last fixed parameter to locate the start of the unnamed argument area. Without at least one named parameter, standard C cannot correctly initialize traversal of the variadic arguments.

Given Data / Assumptions:

• We are following the C standard’s stdarg.h facilities.
• Some nonstandard extensions may exist, but the question targets portable, standard C.

Concept / Approach:
The macro va_start(ap, parmN) expands in a way that depends on the address and calling convention of parmN (the last named parameter). Therefore, a zero-named-parameter signature like func(...) is not valid in standard C for using va_start. Portable variadic functions always declare at least one fixed parameter (e.g., int count, ... or const char *fmt, ...).

Step-by-Step Solution:
Design the API with at least one named parameter (e.g., fmt).Call va_start(ap, fmt); // requires fmt to exist.Use va_arg to retrieve each value in order.Call va_end when done.

Verification / Alternative check:
Look at the standard library’s printf family: printf(const char *fmt, ...). The existence of fmt enables correct va_start behavior. Families like execl also include at least one fixed parameter before ... .

Why Other Options Are Wrong:
“No” conflicts with the stdarg.h contract. References to compiler era or stdio.h are irrelevant. Floating-point is not special here; the rule applies to all types.

Common Pitfalls:
Trying to declare func(...) without a fixed arg; assuming the implementation can somehow infer the boundary automatically.

Final Answer:
Yes