pysimlin: clean up FFI error allocations

pysimlin: clean up FFI error allocations

Ensure JSON patch paths always free collected error objects and release any allocated C strings when name or link counts mismatch. This prevents leaks on error paths and keeps ownership rules consistent.

Assumes libsimlin may partially populate result arrays before reporting a mismatch, so we now free any non-null entries in the allocated range.

Author: bpowers

src/pysimlin/simlin/_ffi.py

@@ -180,14 +180,16 @@ def apply_patch_json(
         out_collected_errors_ptr,
         err_ptr,
     )
-    check_out_error(err_ptr, "Apply JSON patch")
-
     errors: List[ErrorDetail] = []
-    if out_collected_errors_ptr[0] != ffi.NULL:
-        errors = extract_error_details(out_collected_errors_ptr[0])
-        lib.simlin_error_free(out_collected_errors_ptr[0])
-
-    return errors
+    errors_ptr = out_collected_errors_ptr[0]
+    try:
+        check_out_error(err_ptr, "Apply JSON patch")
+        if errors_ptr != ffi.NULL:
+            errors = extract_error_details(errors_ptr)
+        return errors
+    finally:
+        if errors_ptr != ffi.NULL:
+            lib.simlin_error_free(errors_ptr)
 
 
 def serialize_json(project_ptr: Any) -> bytes:

src/pysimlin/simlin/model.py

@@ -251,6 +251,9 @@ def get_incoming_links(self, var_name: str) -> List[str]:
 
         actual_count = int(out_written_ptr[0])
         if actual_count != count:
+            for i in range(count):
+                if c_deps[i] != ffi.NULL:
+                    free_c_string(c_deps[i])
             raise SimlinRuntimeError(
                 f"Failed to get incoming links for '{var_name}': count mismatch (expected {count}, got {actual_count})"
             )

src/pysimlin/simlin/project.py

@@ -135,6 +135,9 @@ def get_model_names(self) -> List[str]:
 
         written = int(out_written_ptr[0])
         if written != count:
+            for i in range(count):
+                if c_names[i] != ffi.NULL:
+                    free_c_string(c_names[i])
             raise SimlinImportError(f"Failed to get model names: got {written}, expected {count}")
 
         # Convert to Python strings and free C memory