To make sure certain symbol names translate into globally unique target symbols.

§1. Pipeline stage. 

void CodeGen::Externals::create_pipeline_stage(void) {
    CodeGen::Stage::new(I"resolve-external-symbols", CodeGen::Externals::run_pipeline_stage, NO_STAGE_ARG, FALSE);
}

int CodeGen::Externals::run_pipeline_stage(pipeline_step *step) {
    Inter::Connectors::stecker(step->repository);
    int resolution_failed = FALSE;
    InterTree::traverse(step->repository, CodeGen::Externals::visitor, &resolution_failed, NULL, PACKAGE_IST);
    if (resolution_failed) internal_error("undefined external link(s)");
    return TRUE;
}

void CodeGen::Externals::visitor(inter_tree *I, inter_tree_node *P, void *state) {
    int *fail_flag = (int *) state;
    inter_package *Q = Inter::Package::defined_by_frame(P);
    if (Site::connectors_package(I) == Q) return;
    inter_symbols_table *ST = Inter::Packages::scope(Q);
    for (int i=0; i<ST->size; i++) {
        inter_symbol *S = ST->symbol_array[i];
        if ((S) && (S->equated_to)) {
            inter_symbol *D = S;
            while ((D) && (D->equated_to)) D = D->equated_to;
            S->equated_to = D;
            if (!Inter::Symbols::is_defined(D)) {
                inter_symbol *socket = Inter::Connectors::find_socket(I, D->symbol_name);
                if (socket) {
                    D = socket->equated_to;
                    S->equated_to = D;
                }
            }
            if (!Inter::Symbols::is_defined(D)) {
                if (Inter::Symbols::get_scope(D) != PLUG_ISYMS) {
                    if (D == S) {
                    LOG("$3 is undefined\n", S);
                    WRITE_TO(STDERR, "Failed to resolve symbol: %S (in ",
                        S->symbol_name, D->symbol_name);
                    } else {
                        LOG("$3 == $3 which is undefined\n", S, D);
                        WRITE_TO(STDERR, "Failed to resolve symbol: %S -> %S (in ",
                            S->symbol_name, D->symbol_name);
                    }
                    Inter::Packages::write_url_name(STDERR, S->owning_table->owning_package);
                    if (D != S) {
                        WRITE_TO(STDERR, "\n   --> "); Inter::Packages::write_url_name(STDERR, D->owning_table->owning_package);
                    }
                    WRITE_TO(STDERR, ")\n");
                    if (fail_flag) *fail_flag = TRUE;
                }
            }
        }
    }
}