How do I use Variadic macros?

To use variadic macros, the ellipsis may be specified as the final formal argument in a macro definition, and the replacement identifier __VA_ARGS__ may be used in the definition to insert the extra arguments. __VA_ARGS__ is replaced by all of the arguments that match the ellipsis, including commas between them.

How can I write a macro which takes a variable number of arguments?

To support variable length arguments in macro, we must include ellipses (…) in macro definition. There is also “__VA_ARGS__” preprocessing identifier which takes care of variable length argument substitutions which are provided to macro.

What is __ Va_opt __?

The sequence __VA_OPT__(x) , which is only legal in the substitution list of a variable-argument macro, expands to x if __VA_ARGS__ is non-empty and to nothing if it is empty. That allows us to fix the LOG macro by suppressing the comma when the argument list is empty: #define LOG(fmt.)

How do you declare a macro in C++?

C++ Preprocessor

Function-Like Macros. You can use #define to define a macro which will take argument as follows −
The # and ## Operators. The # and ## preprocessor operators are available in C++ and ANSI/ISO C.
Predefined C++ Macros. C++ provides a number of predefined macros mentioned below −

What are C++ macros?

Macros: Macros are a piece of code in a program which is given some name. Whenever this name is encountered by the compiler the compiler replaces the name with the actual piece of code. The ‘#define’ directive is used to define a macro.

What is Variadic function in C?

Variadic functions are functions (e.g. printf) which take a variable number of arguments. The declaration of a variadic function uses an ellipsis as the last parameter, e.g. int printf(const char* format.);. See variadic arguments for additional detail on the syntax and automatic argument conversions.

How many arguments macro can have in C?

For portability, you should not have more than 31 parameters for a macro. The parameter list may end with an ellipsis (…).

What are macros in C C++?

What is ## macro C++?

The double-number-sign or token-pasting operator (##), which is sometimes called the merging or combining operator, is used in both object-like and function-like macros. It permits separate tokens to be joined into a single token, and therefore, can’t be the first or last token in the macro definition.

How do C++ macros work?

Are macros good in C++?

Importance of macros in C++ 99.9% of the C++ programs use macros. Macros are very powerful and can do things that not even templates, lambdas, constexpr, inlining or whatever future compiler constructs will ever do.

How do you use variadic arguments?

It takes one fixed argument and then any number of arguments can be passed. The variadic function consists of at least one fixed variable and then an ellipsis(…) as the last parameter….Variadic functions in C.

Methods	Description
va_copy(va_list dest, va_list src)	This makes a copy of the variadic function arguments.

Are there any variadic macros in C + + 11?

Section 16.3 of the C++11 standard specifies variadic macros such that they are compatible with variadic macros from C99 (the second form in the question). In the form of your example “Number 2”, they are standard in C99, and generally a C++ compiler’s preprocessor is the same for C and C++ compilation.

What do you need to know about variadic macros?

Variadic macros are function-like macros that contain a variable number of arguments. Remarks. To use variadic macros, the ellipsis may be specified as the final formal argument in a macro definition, and the replacement identifier __VA_ARGS__ may be used in the definition to insert the extra arguments.

Which is the final argument in a variadic macro?

Variadic macros are function-like macros that contain a variable number of arguments. To use variadic macros, the ellipsis may be specified as the final formal argument in a macro definition, and the replacement identifier __VA_ARGS__ may be used in the definition to insert the extra arguments.

How is the ellipsis replaced in a variadic macro?

https://www.youtube.com/watch?v=QW9tMqJ-CfM