Preprocess

Overview

Optional module. Exposes preprocessed C/C++ source text (macro-expanded, conditionals evaluated, includes resolved). The parser already preprocesses internally — this module is only for accessing the expanded text itself.

Why Use This?

Most workflows don’t need this module. Use it when:

• Debugging macro expansions
• Emitting #line directives mapped to original source
• Displaying preprocessed code to users

The parser class handles preprocessing automatically. Do not preprocess input before calling parser::parse().

Types

Type	Description
preprocessor_context	Stateful preprocessor cache (movable, non-copyable)
preprocessor	File-based preprocessor with context sharing

Functions

preprocessor_context

preprocessor_context()

Default constructor.

preprocessor_context(input, args)

Construct with initial source and compile arguments.

Signature: preprocessor_context(const std::string& input, const compile_args& args = compile_args())

Parameters:

• input — source text defining macros/includes
• args — compiler arguments

apply

Preprocess source text using this context.

Signature: std::string apply(const std::string& to_preprocess, const compile_args& args = compile_args()) const

Parameters:

• to_preprocess — source text to preprocess
• args — compiler arguments

Returns: macro-expanded source text

preprocessor

preprocessor(file, args)

Construct from a single file.

Signature: explicit preprocessor(const file& file, const compile_args& args = compile_args())

preprocessor(files, args)

Construct from multiple files.

Signature: explicit preprocessor(const std::vector<file>& files, const compile_args& args = compile_args())

get_preprocessed_content

Get the expanded source text for each input file.

Signature: const std::vector<std::string>& get_preprocessed_content() const

Returns: vector of preprocessed strings (one per input file)

get_context

Get the reusable preprocessing context.

Signature: const preprocessor_context& get_context() const

Notes:

• Preprocessing is as expensive as parsing (~1MB/s). Avoid unless necessary.
• Output is plain text with no AST structure.
• Context doesn’t track include guards; re-including the same header may cause redefinition warnings.

Example:

// Inspect macro expansion
xccmeta::file f("input.hpp");
xccmeta::preprocessor pp(f, args);
auto expanded = pp.get_preprocessed_content()[0];
std::cout << expanded;

// Share context across files
xccmeta::preprocessor_context ctx("#define PLATFORM_LINUX", args);
auto result1 = ctx.apply(file1.read(), args);
auto result2 = ctx.apply(file2.read(), args);