The C Preprocessor1 Overview1.1 Character sets1.2 Initial processing1.3 Tokenization1.4 The preprocessing language2 Header Files2.1 Include Syntax2.2 Include Operation2.3 Search Path2.4 Once-Only Headers2.5 Alternatives to Wrapper #ifndef2.6 Computed Includes2.7 Wrapper Headers2.8 System Headers3 Macros3.1 Object-like Macros3.2 Function-like Macros3.3 Macro Arguments3.4 Stringification3.5 Concatenation3.6 Variadic Macros3.7 Predefined Macros3.7.1 Standard Predefined Macros3.7.2 Common Predefined Macros3.7.3 System-specific Predefined Macros3.7.4 C++ Named Operators3.8 Undefining and Redefining Macros3.9 Directives Within Macro Arguments3.10 Macro Pitfalls3.10.1 Misnesting3.10.2 Operator Precedence Problems3.10.3 Swallowing the Semicolon3.10.4 Duplication of Side Effects3.10.5 Self-Referential Macros3.10.6 Argument Prescan3.10.7 Newlines in Arguments4 Conditionals4.1 Conditional Uses4.2 Conditional Syntax4.2.1 Ifdef4.2.2 If4.2.3 Defined4.2.4 Else4.2.5 Elif4.3 Deleted Code5 Diagnostics6 Line Control7 Pragmas8 Other Directives9 Preprocessor Output10 Traditional Mode10.1 Traditional lexical analysis10.2 Traditional macros10.3 Traditional miscellany10.4 Traditional warnings11 Implementation Details11.1 Implementation-defined behavior11.2 Implementation limits11.3 Obsolete Features11.3.1 Assertions11.4 Differences from previous versions12 Invocation13 Environment VariablesGNU Free Documentation LicenseADDENDUM: How to use this License for your documentsIndex of DirectivesOption IndexConcept Index