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.

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Overview

Header Files

Macros

Conditionals

Diagnostics

Line Control

Pragmas

Other Directives

Preprocessor Output

Traditional Mode

Implementation Details

Invocation

Environment Variables

GNU Free Documentation License

Option Index

Index of Directives

Concept Index

--- The Detailed Node Listing ---

Overview

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

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

Miscellaneous obsolete features

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