compose: Add a stub "postprocess" entrypoint in Rust

Prep for more code.

Closes: #1726
Approved by: jlebon

rust/src/composepost.rs

@@ -0,0 +1,43 @@
+/*
+ * Copyright (C) 2018 Red Hat, Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+use openat;
+use failure::Fallible;
+
+// This function is called from rpmostree_postprocess_final(); think of
+// it as the bits of that function that we've chosen to implement in Rust.
+fn compose_postprocess_final(_rootfs_dfd: &openat::Dir) -> Fallible<()> {
+    Ok(())
+}
+
+mod ffi {
+    use super::*;
+    use ffiutil::*;
+    use glib_sys;
+    use libc;
+
+    #[no_mangle]
+    pub extern "C" fn ror_compose_postprocess_final(
+        rootfs_dfd: libc::c_int,
+        gerror: *mut *mut glib_sys::GError,
+    ) -> libc::c_int {
+        let rootfs_dfd = ffi_view_openat_dir(rootfs_dfd);
+        int_glib_error(compose_postprocess_final(&rootfs_dfd), gerror)
+    }
+}
+pub use self::ffi::*;

rust/src/lib.rs

@@ -40,6 +40,8 @@ mod ffiutil;
 
 mod treefile;
 pub use treefile::*;
+mod composepost;
+pub use composepost::*;
 mod progress;
 pub use progress::*;
 mod journal;

src/libpriv/rpmostree-postprocess.c

@@ -47,6 +47,7 @@
 #include "rpmostree-core.h"
 #include "rpmostree-json-parsing.h"
 #include "rpmostree-util.h"
+#include "rpmostree-rust.h"
 
 typedef enum {
   RPMOSTREE_POSTPROCESS_BOOT_LOCATION_BOTH,
@@ -958,6 +959,9 @@ rpmostree_postprocess_final (int            rootfs_dfd,
 {
   GLNX_AUTO_PREFIX_ERROR ("Finalizing rootfs", error);
 
+  if (!ror_compose_postprocess_final (rootfs_dfd, error))
+    return FALSE;
+
   /* Use installation of the tmpfiles integration as an "idempotence" marker to
    * avoid doing postprocessing twice, which can happen when mixing `compose
    * postprocess-root` with `compose commit`.