craft-docpath: prove a multi-megabyte UNC path parses iteratively

crates/docpath/tests/long_path.rs

@@ -0,0 +1,29 @@
+//! Paths long enough that a per-level recursive descent would exhaust the stack. Parsing is
+//! iterative — `resolve` and `classify` reach `parse_share` at a fixed depth — so these come
+//! back; a refusal is fine, a crash is not.
+
+use craft_docpath::{classify, resolve};
+
+/// Half a megabyte of components under a UNC share: one component per level for a parser that
+/// recursed on each separator.
+#[test]
+fn a_half_megabyte_unc_path_comes_back() {
+    let mut path = String::from(r"\\?\UNC\host\share");
+    for _ in 0..(1 << 18) {
+        path.push_str(r"\d");
+    }
+    let _ = resolve(&path, None);
+    let _ = classify(&path);
+}
+
+/// Sixteen thousand nested verbatim prefixes: each level was a candidate recursive call when the
+/// UNC prefixes were first reviewed.
+#[test]
+fn nested_verbatim_prefixes_come_back() {
+    let mut path = String::new();
+    for _ in 0..(1 << 14) {
+        path.push_str(r"\\?\UNC\");
+    }
+    let _ = resolve(&path, None);
+    let _ = classify(&path);
+}