libdnf-sys: Drop C API, replace with cxx.rs bridge

Right now, we're using libdnf APIs from Rust via hand-crafted `extern C`
interfaces, which is extra dangerous because there is no signature
checking that happens at compile-time.

Until either we can automate libdnf bindings or use its C++ API directly
via cxx.rs, let's do some basic wrapping in C++ ourselves and use libdnf
through that API only instead. That gives us a lot more confidence and
makes the libdnf API feel more natural to use in Rust.

Cargo.lock

@@ -140,6 +140,16 @@ dependencies = [
  "cc",
 ]
 
+[[package]]
+name = "codespan-reporting"
+version = "0.11.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c6ce42b8998a383572e0a802d859b1f00c79b7b7474e62fff88ee5c2845d9c13"
+dependencies = [
+ "termcolor",
+ "unicode-width",
+]
+
 [[package]]
 name = "console"
 version = "0.14.0"
@@ -259,6 +269,21 @@ dependencies = [
  "link-cplusplus",
 ]
 
+[[package]]
+name = "cxx-build"
+version = "1.0.31"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "69c0ba9a6c36216f1cd3cb6aedc605ca22feb9fc64d9a1b76099a9e368fa553d"
+dependencies = [
+ "cc",
+ "codespan-reporting",
+ "lazy_static",
+ "proc-macro2",
+ "quote",
+ "scratch",
+ "syn",
+]
+
 [[package]]
 name = "cxxbridge-flags"
 version = "1.0.30"
@@ -640,7 +665,8 @@ version = "0.1.0"
 dependencies = [
  "anyhow",
  "cmake",
- "libc",
+ "cxx",
+ "cxx-build",
  "system-deps 2.0.3",
 ]
 
@@ -1246,6 +1272,12 @@ version = "1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d29ab0c6d3fc0ee92fe66e2d99f700eab17a8d57d1c1d3b748380fb20baa78cd"
 
+[[package]]
+name = "scratch"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7e114536316b51a5aa7a0e59fc49661fd263c5507dd08bd28de052e57626ce69"
+
 [[package]]
 name = "serde"
 version = "1.0.123"
@@ -1458,6 +1490,15 @@ dependencies = [
  "winapi",
 ]
 
+[[package]]
+name = "termcolor"
+version = "1.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2dfed899f0eb03f32ee8c6a0aabdb8a7949659e3466561fc0adf54e26d88c5f4"
+dependencies = [
+ "winapi-util",
+]
+
 [[package]]
 name = "terminal_size"
 version = "0.1.16"
@@ -1605,6 +1646,15 @@ version = "0.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ac3b87c63620426dd9b991e5ce0329eff545bccbbb34f3be09ff6fb6ab51b7b6"
 
+[[package]]
+name = "winapi-util"
+version = "0.1.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "70ec6ce85bb158151cae5e5c87f95a8e97d2c0c4b001223f33a334e3ce5de178"
+dependencies = [
+ "winapi",
+]
+
 [[package]]
 name = "winapi-x86_64-pc-windows-gnu"
 version = "0.4.0"

rust/libdnf-sys/Cargo.toml

@@ -6,7 +6,7 @@ edition = "2018"
 links = "dnf"
 
 [dependencies]
-libc = "0.2"
+cxx = "1.0.30"
 
 [lib]
 name = "libdnf_sys"
@@ -16,6 +16,7 @@ path = "lib.rs"
 cmake = "0.1.45"
 system-deps = "2.0"
 anyhow = "1.0"
+cxx-build = "1.0.30"
 
 # This currently needs to duplicate the libraries from libdnf
 [package.metadata.system-deps]
@@ -30,3 +31,4 @@ libcurl = "7"
 sqlite3 = "3"
 modulemd = { name = "modulemd-2.0", version = "2" }
 jsonc = { name = "json-c", version = "0" }
+glib = { name = "glib-2.0", version = "2" }

rust/libdnf-sys/build.rs

@@ -1,9 +1,10 @@
 use anyhow::Result;
 
 fn main() -> Result<()> {
-    system_deps::Config::new().probe()?;
+    let libs = system_deps::Config::new().probe()?;
-    use cmake::Config;
+
-    let libdnf = Config::new("../../libdnf")
+    // first, the submodule proper
+    let libdnf = cmake::Config::new("../../libdnf")
         // Needed for hardened builds
         .cxxflag("-fPIC")
         // I picked /usr/libexec/rpm-ostree just because we need an
@@ -34,5 +35,17 @@ fn main() -> Result<()> {
         libdnf.display()
     );
     println!("cargo:rustc-link-lib=static=dnf");
+
+    // now, our thin cxx.rs bridge wrapper
+    let mut libdnfcxx = cxx_build::bridge("lib.rs");
+    libdnfcxx
+        .file("cxx/libdnf.cxx")
+        .flag("-std=c++17")
+        .include("cxx") // this is needed for cxx.rs' `include!("libdnf.hxx")` to work
+        .include("../../libdnf");
+    // until https://github.com/gdesmott/system-deps/pull/32
+    libdnfcxx.includes(libs.iter().flat_map(|lib| lib.1.include_paths.iter()));
+    libdnfcxx.compile("libdnfcxx.a");
+
     Ok(())
 }

rust/libdnf-sys/cxx/libdnf.cxx

@@ -0,0 +1,44 @@
+/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*-
+ *
+ * Copyright (C) 2021 Red Hat, Inc.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation; either version 2 of the licence or (at
+ * your option) any later version.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General
+ * Public License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place, Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+#include "libdnf.hxx"
+
+namespace dnfcxx {
+  // XXX: use macro to dedupe
+  rust::String dnf_package_get_nevra(DnfPackage &pkg) {
+    return rust::String(::dnf_package_get_nevra(&pkg));
+  }
+  rust::String dnf_package_get_name(DnfPackage &pkg) {
+    return rust::String(::dnf_package_get_name(&pkg));
+  }
+  rust::String dnf_package_get_evr(DnfPackage &pkg) {
+    return rust::String(::dnf_package_get_evr(&pkg));
+  }
+  rust::String dnf_package_get_arch(DnfPackage &pkg) {
+    return rust::String(::dnf_package_get_arch(&pkg));
+  }
+
+  rust::String dnf_repo_get_id(DnfRepo &repo) {
+    return rust::String(::dnf_repo_get_id(&repo));
+  }
+  guint64 dnf_repo_get_timestamp_generated(DnfRepo &repo) {
+    return ::dnf_repo_get_timestamp_generated(&repo);
+  }
+}

rust/libdnf-sys/cxx/libdnf.hxx

@@ -0,0 +1,37 @@
+/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*-
+ *
+ * Copyright (C) 2021 Red Hat, Inc.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation; either version 2 of the licence or (at
+ * your option) any later version.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General
+ * Public License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place, Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+#pragma once
+
+#include <libdnf/libdnf.h>
+
+#include "rust/cxx.h"
+
+namespace dnfcxx {
+  typedef ::DnfPackage DnfPackage;
+  rust::String dnf_package_get_nevra(DnfPackage &pkg);
+  rust::String dnf_package_get_name(DnfPackage &pkg);
+  rust::String dnf_package_get_evr(DnfPackage &pkg);
+  rust::String dnf_package_get_arch(DnfPackage &pkg);
+
+  typedef ::DnfRepo DnfRepo;
+  rust::String dnf_repo_get_id(DnfRepo &repo);
+  guint64 dnf_repo_get_timestamp_generated(DnfRepo &repo);
+}

rust/libdnf-sys/lib.rs

@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0 OR MIT
  */
 
-use libc;
+use cxx::{type_id, ExternType};
 
 /* This is an experiment in calling libdnf functions from Rust. Really, it'd be more sustainable to
  * generate a "libdnf-sys" from SWIG (though it doesn't look like that's supported yet
@@ -13,15 +13,34 @@ use libc;
 
 // This technique for an uninstantiable/opaque type is used by libgit2-sys at least:
 // https://github.com/rust-lang/git2-rs/blob/master/libgit2-sys/lib.rs#L51
+// XXX: dedupe with macro
 pub enum DnfPackage {}
-pub enum DnfRepo {}
+unsafe impl ExternType for DnfPackage {
-
+    type Id = type_id!(dnfcxx::DnfPackage);
-extern "C" {
+    type Kind = cxx::kind::Trivial;
-    pub fn dnf_package_get_nevra(package: *mut DnfPackage) -> *const libc::c_char;
-    pub fn dnf_package_get_name(package: *mut DnfPackage) -> *const libc::c_char;
-    pub fn dnf_package_get_evr(package: *mut DnfPackage) -> *const libc::c_char;
-    pub fn dnf_package_get_arch(package: *mut DnfPackage) -> *const libc::c_char;
-
-    pub fn dnf_repo_get_id(repo: *mut DnfRepo) -> *const libc::c_char;
-    pub fn dnf_repo_get_timestamp_generated(repo: *mut DnfRepo) -> u64;
 }
+
+pub enum DnfRepo {}
+unsafe impl ExternType for DnfRepo {
+    type Id = type_id!(dnfcxx::DnfRepo);
+    type Kind = cxx::kind::Trivial;
+}
+
+#[cxx::bridge(namespace = "dnfcxx")]
+pub mod ffi {
+    unsafe extern "C++" {
+        include!("libdnf.hxx");
+
+        type DnfPackage = crate::DnfPackage;
+        fn dnf_package_get_nevra(pkg: &mut DnfPackage) -> Result<String>;
+        fn dnf_package_get_name(pkg: &mut DnfPackage) -> Result<String>;
+        fn dnf_package_get_evr(pkg: &mut DnfPackage) -> Result<String>;
+        fn dnf_package_get_arch(pkg: &mut DnfPackage) -> Result<String>;
+
+        type DnfRepo = crate::DnfRepo;
+        fn dnf_repo_get_id(repo: &mut DnfRepo) -> Result<String>;
+        fn dnf_repo_get_timestamp_generated(repo: &mut DnfRepo) -> Result<u64>;
+    }
+}
+
+pub use ffi::*;

rust/src/lockfile.rs

@@ -193,7 +193,6 @@ mod ffi {
     use crate::ffiutil::*;
     use crate::includes::*;
     use glib::translate::*;
-    use glib::GString;
     use libdnf_sys::*;
     use std::ptr;
 
@@ -251,9 +250,11 @@ mod ffi {
         };
 
         for pkg in packages {
-            let name: Borrowed<GString> = unsafe { from_glib_borrow(dnf_package_get_name(pkg)) };
+            let pkg_ref = unsafe { &mut *pkg };
-            let evr: Borrowed<GString> = unsafe { from_glib_borrow(dnf_package_get_evr(pkg)) };
+            // XXX: remove unwraps when we move to cxx.rs
-            let arch: Borrowed<GString> = unsafe { from_glib_borrow(dnf_package_get_arch(pkg)) };
+            let name = dnf_package_get_name(pkg_ref).unwrap();
+            let evr = dnf_package_get_evr(pkg_ref).unwrap();
+            let arch = dnf_package_get_arch(pkg_ref).unwrap();
 
             let mut chksum: *mut libc::c_char = ptr::null_mut();
             let r = unsafe { rpmostree_get_repodata_chksum_repr(pkg, &mut chksum, gerror) };
@@ -281,8 +282,9 @@ mod ffi {
             .unwrap();
 
         for rpmmd_repo in rpmmd_repos {
-            let id: String = unsafe { from_glib_none(dnf_repo_get_id(rpmmd_repo)) };
+            let repo_ref = unsafe { &mut *rpmmd_repo };
-            let generated = unsafe { dnf_repo_get_timestamp_generated(rpmmd_repo) };
+            let id = dnf_repo_get_id(repo_ref).unwrap();
+            let generated = dnf_repo_get_timestamp_generated(repo_ref).unwrap();
             lockfile_repos.insert(
                 id,
                 LockfileRepoMetadata {