Variadic functions

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C++ Standard Library
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Utilities library
Type support (basic types, RTTI, type traits) Dynamic memory management Error handling Program utilities Variadic functions Date and time Function objects initializer_list (C++11) bitset hash (C++11) Relational operators rel_ops::operator!= rel_ops::operator> rel_ops::operator<= rel_ops::operator>= Pairs and tuples pair tuple (C++11) piecewise_construct_t (C++11) piecewise_construct (C++11) Swap, forward and move swap forward (C++11) move (C++11) move_if_noexcept (C++11) declval (C++11)
Variadic functions
va_start va_arg va_copy va_end va_list

Variadic functions are functions, such as std::printf, which take a variable number of arguments. To declare a variadic function, ellipsis is used as the last parameter, e.g. int printf(const char *format, ...);. When a variadic function is called, after lvalue-to-rvalue, array-to-pointer, and function-to-pointer conversions, each argument that is a part of the variable argument list, undergoes additional conversions known as default argument promotions: std::nullptr_t is converted to void*, float arguments are converted to double as in floating-point promotion, bool, char, short, and unscoped enumerations are converted to int or wider integer types as in integer promotion. Only arithmetic, enumeration, pointer, pointer to member, and class type arguments are allowed.

Variadic templates, which can also be used to create functions that take variable number of arguments, are often the better choice because they do not impose restrictions on the types of the arguments, do not perform integral and floating-point promotions, and are type safe. (since C++11)

Defined in header <cstdarg>
va_start	enables access to variadic function arguments (function macro)
va_arg	accesses the next variadic function argument (function macro)
va_copy (C++11)	makes a copy of the variadic function arguments (function macro)
va_end	ends traversal of the variadic function arguments (function macro)
va_list	holds the information needed by va_start, va_arg, va_end, and va_copy (class)