Skip to Main Content
C++ In a Nutshell
book

C++ In a Nutshell

by Ray Lischner
May 2003
Intermediate to advanced content levelIntermediate to advanced
808 pages
32h 24m
English
O'Reilly Media, Inc.
Content preview from C++ In a Nutshell

<cstdarg>

The <cstdarg> header is the C++ version of the C standard <stdarg.h> header, which declares macros for accessing the arguments to a function that takes a variable number of arguments, that is, a function that is declared with an ellipsis as the last parameter.

A function that takes a variable number of arguments (called a variadic function) must have some way of knowing how many arguments have actually been passed to the function and what their types are. For example, the printf function (in <cstdio>) uses its format string to determine the number and type of arguments.

Example 13-8 shows how a function can use the <cstdarg> macros. The max function takes at least two arguments. The first is a count of the number of remaining arguments; the count must be positive. The template parameter specifies the type of each argument that follows the count.

Example 13-8. Finding the maximum value of any number of arguments
#include <cassert> #include <cstdarg> // Use a trivial wrapper class to ensure that va_end is called. class varargs { public: ~varargs( ) { va_end(ap); } std::va_list& ap; }; template <typename T> T max(unsigned count, ...) { assert(count > 0); varargs va; va_start(va.ap, count); T result = va_arg(va.ap, T); // Get first argument. while (--count > 0) { T arg = va_arg(va.ap, T); // Get successive arguments. if (arg > result) result = arg; // Remember the largest. } return result; } int main( ) { int a, b, c, d; ... int x = max<int>(4, a, b, c, d); int y = max<int>(2, ...
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.
Start your free trial

You might also like

C++ High Performance

C++ High Performance

Viktor Sehr, Björn Andrist
Optimized C++

Optimized C++

Kurt Guntheroth
Mastering C++ Programming

Mastering C++ Programming

Jeganathan Swaminathan

Publisher Resources

ISBN: 059600298XSupplemental ContentErrata Page