Utility methods for artificial debug types in the generated DWARF (#1482)

* add operator*
* add operator->
* add ptr() unwrap method
* comments/refactor
* macro_rules
* external symbols workaround

tests/debug/lldb.rs

@@ -92,3 +92,37 @@ check: exited with status
     )?;
     Ok(())
 }
+
+#[test]
+#[ignore]
+#[cfg(all(
+    any(target_os = "linux", target_os = "macos"),
+    target_pointer_width = "64"
+))]
+pub fn test_debug_dwarf_ptr() -> Result<()> {
+    let output = lldb_with_script(
+        &[
+            "-g",
+            "--opt-level",
+            "0",
+            "tests/debug/testsuite/reverse-str.wasm",
+        ],
+        r#"b reverse-str.c:9
+r
+p __vmctx->set(),&*s
+c"#,
+    )?;
+
+    check_lldb_output(
+        &output,
+        r#"
+check: Breakpoint 1: no locations (pending)
+check: stop reason = breakpoint 1.1
+check: frame #0
+sameln: reverse(s=(__ptr =
+check: "Hello, world."
+check: resuming
+"#,
+    )?;
+    Ok(())
+}

tests/debug/testsuite/reverse-str.c

@@ -0,0 +1,21 @@
+// Compile with:
+//   clang --target=wasm32 reverse-str.c -o reverse-str.wasm -g \
+//     -O0 -nostdlib -fdebug-prefix-map=$PWD=.
+#include <stdlib.h>
+
+void reverse(char *s, size_t len)
+{
+    if (!len) return;
+    size_t i = 0, j = len - 1;
+    while (i < j) {
+        char t = s[i];
+        s[i++] = s[j];
+        s[j--] = t;
+    }
+}
+
+void _start()
+{
+    char hello[] = "Hello, world.";
+    reverse(hello, 13);
+}