: The caller must still know the order or use "sentinel" values (like NULL ) to mark the end of the argument list. Summary of Techniques Supports Named? Supports Optional? Standard Requirement Standard Positional Struct + Initializer Yes (defaults to 0) C99 or later Variadic Macros Yes (via struct) C99 or later stdarg.h Yes (manual)
The most common way to simulate named parameters is to pass a single struct to a function. By using C99 designated initializers, you can specify values for specific members by name.
Standard C (ANSI C, C99, C11, etc.) does not natively support named or optional parameters in the way languages like C# or Python do. However, you can emulate this behavior by using a combination of , designated initializers , and variadic macros . 1. Using Structs and Designated Initializers How to use named and optional parameters in C
For a more "classic" C approach, you can use variadic functions, though these do not provide true named parameters and are harder to use safely.
#include // Define a struct to hold "parameters" typedef struct { int width; int height; const char *title; // Optional (defaults to NULL) } WindowArgs; void create_window(WindowArgs args) { printf("Window: %s (%dx%d)\n", args.title ? args.title : "Untitled", args.width, args.height); } int main() { // Named and optional call using a compound literal create_window((WindowArgs){.width = 800, .height = 600}); // Changing order and including all fields create_window((WindowArgs){.title = "Game", .height = 1080, .width = 1920}); return 0; } Use code with caution. Copied to clipboard 2. Enhancing with Macros for Cleaner Syntax : The caller must still know the order
: Used to retrieve an indefinite number of arguments.
Struct members not explicitly initialized are automatically set to zero or NULL by the compiler, effectively making them "optional". Example Implementation: However, you can emulate this behavior by using
You explicitly name the struct members in the function call.