preserve errno in OSError

Author: dhalbert

extmod/vfs_fat_file.c

@@ -28,6 +28,7 @@
 #if MICROPY_VFS && MICROPY_VFS_FAT
 
 #include <stdio.h>
+#include <string.h>
 
 #include "py/runtime.h"
 #include "py/stream.h"
@@ -199,7 +200,7 @@ STATIC mp_obj_t file_open(fs_user_mount_t *vfs, const mp_obj_type_t *type, mp_ar
     FRESULT res = f_open(&vfs->fatfs, &o->fp, fname, mode);
     if (res != FR_OK) {
         m_del_obj(pyb_file_obj_t, o);
-        mp_raise_OSError_errno_str(fresult_to_errno_table[res], fname);
+        mp_raise_OSError_errno_str(fresult_to_errno_table[res], args[0].u_obj);
     }
     // If we're reading, turn on fast seek.
     if (mode == FA_READ) {

py/objexcept.c

@@ -112,14 +112,17 @@ void mp_obj_exception_print(const mp_print_t *print, mp_obj_t o_in, mp_print_kin
         if (o->args == NULL || o->args->len == 0) {
             mp_print_str(print, "");
             return;
-        } else if (o->args->len == 1) {
-            // try to provide a nice OSError error message
+        } else if (o->args->len <= 2) {
+            // try to provide a nice OSError error message; second arg might exist (e.g. filename).
             if (MP_OBJ_IS_SMALL_INT(o->args->items[0]) &&
                 mp_obj_is_subclass_fast(MP_OBJ_FROM_PTR(o->base.type), MP_OBJ_FROM_PTR(&mp_type_OSError))) {
                 char decompressed[50];
                 const char *msg = mp_common_errno_to_str(o->args->items[0], decompressed, sizeof(decompressed));
                 if (msg != NULL) {
                     mp_printf(print, "[Errno " INT_FMT "] %s", MP_OBJ_SMALL_INT_VALUE(o->args->items[0]), msg);
+                    if (o->args->len == 2) {
+                        mp_printf(print, ": '%s'", mp_obj_str_get_str(o->args->items[1]));
+                    }
                     return;
                 }
             }

py/runtime.c

@@ -1578,11 +1578,12 @@ NORETURN void mp_raise_OSError_msg(const compressed_string_t *msg) {
     mp_raise_msg(&mp_type_OSError, msg);
 }
 
-NORETURN void mp_raise_OSError_errno_str(int errno_, const char *str) {
-    char decompressed[50];
-    const char *errno_str = mp_common_errno_to_str(MP_OBJ_NEW_SMALL_INT(errno_),
-                                                   decompressed, sizeof(decompressed));
-    mp_raise_OSError_msg_varg(translate("[Errno %d] %s: %s"), errno_, errno_str, str);
+NORETURN void mp_raise_OSError_errno_str(int errno_, mp_obj_t str) {
+    mp_obj_t args[2] = {
+        MP_OBJ_NEW_SMALL_INT(errno_),
+        str,
+    };
+    nlr_raise(mp_obj_new_exception_args(&mp_type_OSError, 2, args));
 }
 
 NORETURN void mp_raise_OSError_msg_varg(const compressed_string_t *fmt, ...) {

py/runtime.h

@@ -161,7 +161,7 @@ NORETURN void mp_raise_RuntimeError(const compressed_string_t *msg);
 NORETURN void mp_raise_ImportError(const compressed_string_t *msg);
 NORETURN void mp_raise_IndexError(const compressed_string_t *msg);
 NORETURN void mp_raise_OSError(int errno_);
-NORETURN void mp_raise_OSError_errno_str(int errno_, const char *str);
+NORETURN void mp_raise_OSError_errno_str(int errno_, mp_obj_t str);
 NORETURN void mp_raise_OSError_msg(const compressed_string_t *msg);
 NORETURN void mp_raise_OSError_msg_varg(const compressed_string_t *fmt, ...);
 NORETURN void mp_raise_NotImplementedError(const compressed_string_t *msg);