Return searched paths from find_libffi_dll for error reporting

1 files changed, 11 insertions, 7 deletions

diff --git a/tools/build_gui.py b/tools/build_gui.py
index e912d8d..c9811a3 100644
--- a/tools/build_gui.py
+++ b/tools/build_gui.py
@@ -10,7 +10,7 @@ except ImportError:
     sys.exit(1)
 
 
-def find_libffi_dll() -> str | None:
+def find_libffi_dll() -> tuple[str | None, list[str]]:
     """
     Find the libffi-*.dll file required for _ctypes on Windows.
 
@@ -18,9 +18,13 @@ def find_libffi_dll() -> str | None:
     1. The active Python environment's DLLs directory.
     2. The base Python installation's DLLs directory (if in a venv).
     3. A Conda environment's Library/bin directory.
+
+    Returns:
+        A tuple containing the path to the DLL (or None) and a list of
+        directories that were searched.
     """
     if sys.platform != "win32":
-        return None
+        return None, []
 
     search_paths = []
     # 1. Active environment's DLLs directory (sys.prefix is the venv path)
@@ -45,9 +49,9 @@ def find_libffi_dll() -> str | None:
         if found_dlls:
             dll_path = found_dlls[0]
             print(f"  - Found: {dll_path}")
-            return dll_path
+            return dll_path, unique_paths
 
-    return None
+    return None, unique_paths
 
 
 def main() -> None:
@@ -67,7 +71,7 @@ def main() -> None:
     ]
 
     if sys.platform == "win32":
-        libffi_path = find_libffi_dll()
+        libffi_path, searched_paths = find_libffi_dll()
         if libffi_path:
             # The format for --add-binary is "source;destination" on Windows.
             # We add the DLL to the root of the bundle.
@@ -76,8 +80,8 @@ def main() -> None:
             print("\nERROR: Could not find libffi-*.dll on Windows.")
             print("This DLL is required for the _ctypes module to work correctly.")
             print("Searched in the following directories:")
-            for path in sorted(list(set(p for p in search_paths if os.path.isdir(p)))):
-                 print(f"  - {path}")
+            for path in searched_paths:
+                print(f"  - {path}")
             print("Please ensure you are using a standard CPython or Conda installation.")
             sys.exit(1)