libfprint: Use a macro to easily compute TOD padding

libfprint/fpi-assembling.h

@@ -20,6 +20,7 @@
 #pragma once
 
 #include "fp-image.h"
+#include "tod/tod-macros.h"
 
 /**
  * fpi_frame:
@@ -110,7 +111,9 @@ struct fpi_line_asmbl_ctx
   unsigned char (*get_pixel)(struct fpi_line_asmbl_ctx *ctx,
                              GSList                    *line,
                              unsigned int               x);
-  gpointer _padding_dummy[32];
+
+  /*< private >*/
+  TOD_PADDING (32, 0);
 };
 
 FpImage *fpi_assemble_lines (struct fpi_line_asmbl_ctx *ctx,

libfprint/fpi-device.h

@@ -23,6 +23,7 @@
 #include "fp-device.h"
 #include "fp-image.h"
 #include "fpi-print.h"
+#include "tod/tod-macros.h"
 
 /**
  * FpiDeviceUdevSubtype:
@@ -73,13 +74,10 @@ struct _FpIdEntry
 
   /*< private >*/
   /* padding for future expansion */
-#if GLIB_SIZEOF_VOID_P == 8
-  gpointer _padding_dummy[13];
-#elif GLIB_SIZEOF_VOID_P == 4
-  gpointer _padding_dummy[11];
-#else
-  G_STATIC_ASSERT("Unexpected pointer size")
-#endif
+  TOD_PADDING_ALIGNED (16,
+                       sizeof (guint) * 2 +
+                       sizeof (FpiDeviceUdevSubtypeFlags) +
+                       sizeof (gpointer));
 };
 
 /**
@@ -192,13 +190,10 @@ struct _FpDeviceClass
 
   /*< private >*/
   /* padding for future expansion */
-#if GLIB_SIZEOF_VOID_P == 8
-  gpointer _padding_dummy[27];
-#elif GLIB_SIZEOF_VOID_P == 4
-  gpointer _padding_dummy[26];
-#else
-  G_STATIC_ASSERT("Unexpected pointer size")
-#endif
+  TOD_PADDING_ALIGNED8 (32,
+                        sizeof (FpDeviceFeature) +
+                        sizeof (gint32) * 2 +
+                        sizeof (gpointer) * 3);
 };
 
 void fpi_device_class_auto_initialize_features (FpDeviceClass *device_class);

libfprint/fpi-image-device.h

@@ -117,7 +117,7 @@ struct _FpImageDeviceClass
 
   /*< private >*/
   /* padding for future expansion */
-  gpointer _padding_dummy[32];
+  TOD_PADDING (32, 0);
 };
 
 void fpi_image_device_set_bz3_threshold (FpImageDevice *self,

libfprint/fpi-image.h

@@ -21,6 +21,7 @@
 #pragma once
 
 #include "fp-image.h"
+#include "tod/tod-macros.h"
 
 /**
  * FpiImageFlags:
@@ -69,7 +70,7 @@ struct _FpImage
   GPtrArray *minutiae;
   guint      ref_count;
 
-  gpointer   _padding_dummy[32];
+  TOD_PADDING (32, 0);
 };
 
 gint fpi_std_sq_dev (const guint8 *buf,

libfprint/fpi-spi-transfer.h

@@ -75,7 +75,7 @@ struct _FpiSpiTransfer
   GDestroyNotify free_buffer_rd;
 
   /* padding for future expansion */
-  gpointer _padding_dummy[32];
+  TOD_PADDING (32, 0);
 };
 
 GType              fpi_spi_transfer_get_type (void) G_GNUC_CONST;

libfprint/fpi-usb-transfer.h

@@ -103,9 +103,8 @@ struct _FpiUsbTransfer
   /* Data free function */
   GDestroyNotify free_buffer;
 
-  /*< private >*/
   /* padding for future expansion */
-  gpointer _padding_dummy[32];
+  TOD_PADDING (32, 0);
 };
 
 GType              fpi_usb_transfer_get_type (void) G_GNUC_CONST;

libfprint/tod/tod-macros.h

@@ -0,0 +1,32 @@
+/*
+ * Shared library loader for libfprint
+ * Copyright (C) 2021 Marco Trevisan <marco.trevisan@canonical.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#pragma once
+
+#define TOD_PADDING(original, wasted) \
+  char _tod_expansion_padding[(GLIB_SIZEOF_VOID_P * (original)) - (wasted)];
+
+#define TOD_PADDING_ALIGNED(original, wasted) \
+  TOD_PADDING (original, (wasted) + GLIB_SIZEOF_VOID_P)
+
+#define TOD_PADDING_ALIGNED4(original, wasted) \
+  TOD_PADDING (original, (wasted) + (GLIB_SIZEOF_VOID_P == 4 ? GLIB_SIZEOF_VOID_P : 0))
+
+#define TOD_PADDING_ALIGNED8(original, wasted) \
+  TOD_PADDING (original, (wasted) + (GLIB_SIZEOF_VOID_P == 8 ? GLIB_SIZEOF_VOID_P : 0))