Require _Z* when doing C++ demangling

crates/environ/src/demangling.rs

@@ -7,10 +7,14 @@ pub fn demangle_function_name(writer: &mut impl core::fmt::Write, name: &str) ->
     #[cfg(feature = "demangle")]
     if let Ok(demangled) = rustc_demangle::try_demangle(name) {
         return write!(writer, "{demangled}");
-    } else if let Ok(symbol) = cpp_demangle::Symbol::new(name) {
-        if let Ok(demangled) = symbol.demangle() {
-            return write!(writer, "{demangled}");
-        }
+    } else if name.starts_with("_Z")
+        // Only attempt to demangle Itanium C++ mangled symbols, which all
+        // start with `_Z`, as otherwise short names such as `i` are
+        // "demangled" as types such as `int`.
+        && let Ok(symbol) = cpp_demangle::Symbol::new(name)
+        && let Ok(demangled) = symbol.demangle()
+    {
+        return write!(writer, "{demangled}");
     }
 
     write!(writer, "{name}")

tests/all/traps.rs

@@ -323,6 +323,36 @@ error while executing at wasm backtrace:
     Ok(())
 }
 
+#[test]
+fn trap_display_demangled_names() -> Result<()> {
+    let mut store = Store::<()>::default();
+    let wat = r#"
+        (module $m
+            (func $c unreachable)
+            (func $i call $c)
+            (func $_Z3foov call $i)
+            (func (export "bar") call $_Z3foov)
+        )
+    "#;
+
+    let module = Module::new(store.engine(), wat)?;
+    let instance = Instance::new(&mut store, &module, &[])?;
+    let run_func = instance.get_typed_func::<(), ()>(&mut store, "bar")?;
+
+    // Short names like `c` and `i` shouldn't be "demangled" as C++ types, but
+    // C++ mangled names should still be demangled.
+    let e = run_func.call(&mut store, ()).unwrap_err();
+    e.assert_contains(
+        "\
+error while executing at wasm backtrace:
+    0:     0x23 - m!c
+    1:     0x27 - m!i
+    2:     0x2c - m!foo()
+    3:     0x31 - m!<wasm function 3>",
+    );
+    Ok(())
+}
+
 #[test]
 fn trap_display_multi_module() -> Result<()> {
     let mut store = Store::<()>::default();