The C Preprocessor

The C Preprocessor

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
• Computed Includes
• Wrapper Headers
• System Headers

Macros

• Object-like Macros
• Function-like Macros
• Macro Arguments
• Stringification
• 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
• Differences from previous versions

Obsolete Features

• Assertions
• Obsolete once-only headers

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