The C Preprocessor

Table of Contents

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The C preprocessor implements the macro language used to transform C, C++, and Objective-C programs before they are compiled. It can also be useful on its own.

• Overview:  
• Header Files:  
• Macros:  
• Conditionals:  
• Diagnostics:  
• Line Control:  
• Pragmas:  
• Other Directives:  
• Preprocessor Output:  
• Traditional Mode:  
• Implementation Details:  
• Invocation:  
• Environment Variables:  
• GNU Free Documentation License:  
• Index of Directives:  
• Option Index:  
• Concept Index:   


 — The Detailed Node Listing —

Overview
• Character sets:  
• Initial processing:  
• Tokenization:  
• The preprocessing language:   

Header Files
• Include Syntax:  
• Include Operation:  
• Search Path:  
• Once-Only Headers:  
• Alternatives to Wrapper #ifndef:  
• Computed Includes:  
• Wrapper Headers:  
• System Headers:   

Macros
• Object-like Macros:  
• Function-like Macros:  
• Macro Arguments:  
• Stringizing:  
• Concatenation:  
• Variadic Macros:  
• Predefined Macros:  
• Undefining and Redefining Macros:  
• Directives Within Macro Arguments:  
• Macro Pitfalls:   

Predefined Macros
• Standard Predefined Macros:  
• Common Predefined Macros:  
• System-specific Predefined Macros:  
• C++ Named Operators:   

Macro Pitfalls
• Misnesting:  
• Operator Precedence Problems:  
• Swallowing the Semicolon:  
• Duplication of Side Effects:  
• Self-Referential Macros:  
• Argument Prescan:  
• Newlines in Arguments:   

Conditionals
• Conditional Uses:  
• Conditional Syntax:  
• Deleted Code:   

Conditional Syntax
• Ifdef:  
• If:  
• Defined:  
• Else:  
• Elif:   

Implementation Details
• Implementation-defined behavior:  
• Implementation limits:  
• Obsolete Features:   

Obsolete Features
• Obsolete Features:  

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