#assert: Assertions
#define: Object-like Macros
#elif: Elif
#else: Else
#endif: Ifdef
#error: Diagnostics
#ident: Other Directives
#if: Conditional Syntax
#ifdef: Ifdef
#ifndef: Ifdef
#import: Obsolete once-only headers
#include: Include Syntax
#include_next: Wrapper Headers
#line: Line Control
#pragma GCC dependency: Pragmas
#pragma GCC poison: Pragmas
#pragma GCC system_header: Pragmas, System Headers
#sccs: Other Directives
#unassert: Assertions
#undef: Undefining and Redefining Macros
#warning: Diagnostics
C_INCLUDE_PATH: Environment Variables
CPATH: Environment Variables
CPLUS_INCLUDE_PATH: Environment Variables
DEPENDENCIES_OUTPUT: Environment Variables
OBJC_INCLUDE_PATH: Environment Variables
SUNPRO_DEPENDENCIES: Environment Variables