Call C functions from Gofra

This guide shows how to call functions from a C library in Gofra.

For background on FFI, see Wikipedia. For the extern attribute, see Reference: attributes.

Declare the external function

Mark the function with extern and give it a Gofra type contract:

extern func int puts[*char[] s]

This matches the C declaration:

int puts(const char *s);

extern functions cannot have a body — only a signature.

Tell the linker which library to link against with -l:

gofra build hello.gof -lraylib

If the library is not found by pkg-config, add a search directory with -L:

gofra build hello.gof -lraylib -L/opt/homebrew/lib --no-pkg-config

extern func int puts[*char[] s]

func void main[]
    "Hello, World!" puts drop
end

gofra build hello.gof -lc

puts is called with a C-string; its return value is dropped.

Gofra does not support calling variadic C functions (printf, etc.) directly. The workaround is to write a non-variadic wrapper in C and call that:

extern functions use the C calling convention. Gofra functions use the Gofra calling convention. They are not interchangeable.