Function Declarations

Parsing Function Signatures

Function declarations introduce a name, parameter list, and return type into the program's structure. Clang's ParseFunctionDefinition and GCC's declarator parsing handle prototypes vs definitions, variadic parameters, and pointer return types. Getting signatures right here feeds directly into type checking.

Grammar Sketch

A declaration looks like type name(type param, ...) { body } or a prototype ending in ;. The parser must collect parameter names and types, build an AST node, and distinguish forward declarations from definitions with bodies.

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• Parameter list may be empty: void foo(void) vs void foo()
• Return type can be pointer or struct name
• Prototypes end with semicolon; definitions have a block body
• Store parameter types for signature checking later

Connecting to real compilers

Production compilers embed this step inside a longer pipeline. GCC flows through cpp, cc1, assembly, and ld; Clang uses the driver, Sema, LLVM IR passes, and a target backend. LLVM bitcode, JVM bytecode, and WASM are other familiar IRs at the same layer. The exercise isolates one pass so you can test it alone before chaining it to the next stage.

Why for this exercise

You will parse function declarations and definitions including parameter lists and return types. This exercise requires building AST nodes that carry full function signatures for the semantic analysis pass to validate call sites.