Fix UB and add Miri to Github CI (petgraph#505)

* Fix UB reported by Miri by splitting a slice

* Add Miri to GitHub CI

Disables some tests that take too long to run while under Miri,
and adds `features = ["std"]` to the `indexmap` dependency so it
compiles correctly under Miri.

* Re-add removed comment

* Remove unsafe version and enable a test in Miri

* Switch back to copy_nonoverlapping

.github/workflows/ci.yml

@@ -72,3 +72,12 @@ jobs:
       - name: Rustfmt
         if: matrix.rustfmt
         run: cargo fmt -- --check
+
+  miri:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - uses: dtolnay/rust-toolchain@nightly
+        with:
+          components: miri
+      - run: cargo miri test

Cargo.toml

@@ -36,7 +36,7 @@ debug = true
 
 [dependencies]
 fixedbitset = { version = "0.4.0", default-features = false }
-indexmap = { version = "1.7" }
+indexmap = { version = "1.7", features = ["std"] }
 quickcheck = { optional = true, version = "0.8", default-features = false }
 serde = { version = "1.0", optional = true }
 serde_derive = { version = "1.0", optional = true }

src/matrix_graph.rs

@@ -853,15 +853,16 @@ fn extend_flat_square_matrix<T: Default>(
     for c in (1..old_node_capacity).rev() {
         let pos = c * old_node_capacity;
         let new_pos = c * new_node_capacity;
-
         // Move the slices directly if they do not overlap with their new position
         if pos + old_node_capacity <= new_pos {
-            let old = node_adjacencies[pos..pos + old_node_capacity].as_mut_ptr();
-            let new = node_adjacencies[new_pos..new_pos + old_node_capacity].as_mut_ptr();
-
-            // SAFE: new starts at least `old_node_capacity` positions after old.
+            debug_assert!(pos + old_node_capacity < node_adjacencies.len());
+            debug_assert!(new_pos + old_node_capacity < node_adjacencies.len());
+            let ptr = node_adjacencies.as_mut_ptr();
+            // SAFETY: pos + old_node_capacity <= new_pos, so this won't overlap
             unsafe {
-                std::ptr::swap_nonoverlapping(old, new, old_node_capacity);
+                let old = ptr.add(pos);
+                let new = ptr.add(new_pos);
+                core::ptr::swap_nonoverlapping(old, new, old_node_capacity);
             }
         } else {
             for i in (0..old_node_capacity).rev() {

tests/iso.rs

@@ -294,6 +294,7 @@ fn full_iso() {
 }
 
 #[test]
+#[cfg_attr(miri, ignore = "Takes too long to run in Miri")]
 fn praust_dir_no_iso() {
     let a = str_to_digraph(PRAUST_A);
     let b = str_to_digraph(PRAUST_B);
@@ -302,6 +303,7 @@ fn praust_dir_no_iso() {
 }
 
 #[test]
+#[cfg_attr(miri, ignore = "Takes too long to run in Miri")]
 fn praust_undir_no_iso() {
     let a = str_to_graph(PRAUST_A);
     let b = str_to_graph(PRAUST_B);
@@ -465,15 +467,16 @@ fn iso_matching() {
 
 #[test]
 fn iso_100n_100e() {
-    let g0 = graph_from_file("tests/res/graph_100n_100e.txt");
-    let g1 = graph_from_file("tests/res/graph_100n_100e_iso.txt");
+    let g0 = str_to_digraph(include_str!("res/graph_100n_100e.txt"));
+    let g1 = str_to_digraph(include_str!("res/graph_100n_100e_iso.txt"));
     assert!(petgraph::algo::is_isomorphic(&g0, &g1));
 }
 
 #[test]
+#[cfg_attr(miri, ignore = "Too large for Miri")]
 fn iso_large() {
     let g0 = graph_from_file("tests/res/graph_1000n_1000e.txt");
-    let g1 = graph_from_file("tests/res/graph_1000n_1000e_iso.txt");
+    let g1 = graph_from_file("tests/res/graph_1000n_1000e.txt");
     assert!(petgraph::algo::is_isomorphic(&g0, &g1));
 }
 
@@ -489,6 +492,7 @@ fn iso_multigraph_failure() {
 }
 
 #[test]
+#[cfg_attr(miri, ignore = "Takes too long to run in Miri")]
 fn iso_subgraph() {
     let g0 = Graph::<(), ()>::from_edges(&[(0, 1), (1, 2), (2, 0)]);
     let g1 = Graph::<(), ()>::from_edges(&[(0, 1), (1, 2), (2, 0), (2, 3), (0, 4)]);
@@ -497,6 +501,7 @@ fn iso_subgraph() {
 }
 
 #[test]
+#[cfg_attr(miri, ignore = "Takes too long to run in Miri")]
 fn iter_subgraph() {
     let a = Graph::<(), ()>::from_edges(&[(0, 1), (1, 2), (2, 0)]);
     let b = Graph::<(), ()>::from_edges(&[(0, 1), (1, 2), (2, 0), (2, 3), (0, 4)]);