Can you use else for Ifdef?

Can you use else for Ifdef?

Yes, it’s legal pre-processor speak. An else-if after an if. But, try not to rely too much on pre-processor magic. @RemyLebeau Yes, we can use #ifdef with #elif .

What does Ifdef mean in C?

Description. In the C Programming Language, the #ifdef directive allows for conditional compilation. The preprocessor determines if the provided macro exists before including the subsequent code in the compilation process.

How do you write Ifdef?

The #ifdef preprocessor directive checks if macro is defined by #define. If yes, it executes the code otherwise #else code is executed, if present….Syntax with #else:

1. #ifdef MACRO.
2. //successful code.
3. #else.
4. //else code.
5. #endif.

What are the various conditional syntax of preprocessor in C?

The preprocessor conditional compilation directive spans several lines: The condition specification line (beginning with #if , #ifdef , or #ifndef ) Lines containing code that the preprocessor passes on to the compiler if the condition evaluates to a nonzero value (optional) The #elif line (optional)

What is ifdef and endif in C++?

#ifdef means if defined. If the symbol following #ifdef is defined, either using #define in prior source code or using a compiler command-line argument, the text up to the enclosing #endif is included by the preprocessor and therefore compiled. #if works similarly, but it evaluates the boolean expression following it.

What does Ifdef mean in C++?

#ifdef: This directive is the simplest conditional directive. This block is called a conditional group. The controlled text will get included in the preprocessor output iff the macroname is defined. The controlled text inside a conditional will embrace preprocessing directives.

What does Ifdef mean?

if the following is defined
ifdef means “if the following is defined” while ifndef means “if the following is not defined”.

What is Ifndef C?

In the C Programming Language, the #ifndef directive allows for conditional compilation. The preprocessor determines if the provided macro does not exist before including the subsequent code in the compilation process.

What is the use of ifdef in C++?

The #ifdef directive is useful for checking whether a definition exists, because a definition can be passed from the command line. For example: // ifdef_ifndef.CPP // compile with: /Dtest /c #ifndef test #define final #endif END Microsoft Specific. See also. Preprocessor directives

What is the difference between the ifdef and ifndef directives?

The #ifdef and #ifndef directives have the same effect as the #if directive when it’s used with the defined operator. Syntax. These directives are equivalent to: Remarks. You can use the #ifdef and #ifndef directives anywhere #if can be used. The #ifdef identifier statement is equivalent to #if 1 when identifier has been defined.

What is the correct syntax for ifdef identifier newline?

The #ifdefdirective has the following syntax: #ifdef identifier newline This directive checks whether the identifier is currently defined. Identifiers can be defined by a #definedirective or on the command line. If such identifiers have not been subsequently undefined, they are considered currently defined.

What is the use of if-else directive in C++?

#else directive is used to provide an alternate statements need to be executed when the condition given using #if, #ifdef or #ifndef. Whenever the condition returns false compiler sends the control directly to the #else block statement. There are certain rules need to be followed for declaring conditional expression: