Export C to Go

c2go_extern exports a defined C function through the generated package. Managed record metadata lets c2go-bind expose a matching Go-visible layout.

Export a function

#include <c2go.h>
#include <stddef.h>
#include <stdint.h>

c2go_extern int64_t sum(const int64_t *values, size_t count) {
    int64_t total = 0;
    for (size_t i = 0; i < count; ++i) {
        total += values[i];
    }
    return total;
}

Prefer fixed-width integers in public APIs. long is 64 bits on 64-bit Linux and macOS targets but remains 32 bits on 64-bit Windows; do not use it for a cross-platform Go API unless that difference is intentional.

The default Go export name converts each underscore-separated segment to CamelCase and removes the underscores: sum becomes Sum, is_upper becomes IsUpper, and sqlite3_open becomes Sqlite3Open. Set the final Go import path only with c2go-clang -fc2go-package; the manifest carries it to the binder.

Use c2go_extern_as(C2GO_KEEPCASE) only when exact spelling is part of an existing contract:

c2go_extern_as(C2GO_KEEPCASE)
int ParseID(const char *text) { /* ... */ }

Declarations and definitions must agree. Put c2go_extern on the first declaration; adding it only on a later redeclaration is rejected.

Export a managed record

struct managed Point {
    double x;
    double y;
};

c2go_extern struct Point translate(
    struct Point point,
    double dx,
    double dy
) {
    point.x += dx;
    point.y += dy;
    return point;
}

The manifest records size, field offsets, and pointer layout. c2go-bind uses those facts to generate a Go-compatible type rather than guessing from host compiler defaults.

Packed or custom-aligned managed records produce C2Go warnings. The current manifest/binder path can describe explicit padding, but the resulting public layout is target-specific and must be checked in the generated Go type. An unmanaged record that contains a GC-scanned data pointer is stricter: packing or custom alignment is rejected because the conservative scanner would miss a shifted pointer word.

Names reserved by Go

An exported init or main function cannot retain a lowercase name. These names have language-level meaning in Go, so C2Go rejects an export that would collide with them.

Keep the generated package intact

Generated files include ABI/version guards and may include runtime imports, GC metadata, or native-call glue in addition to the visible declarations. Do not copy only the public-looking .go file. Keep the complete generated directory and its licensing records together.

Next, learn how memory and Go GC rules keep exported pointer layouts visible to the collector.