[gdk-pixbuf] ico: Don't use signed ints to do uints offset arithmetics

[Bastien Nocera <hadess src gnome org>]

commit e08c11540bec325189b621666b1fa5e58178693d
Author: Bastien Nocera <hadess hadess net>
Date:   Thu Jul 13 22:12:06 2017 +0200

    ico: Don't use signed ints to do uints offset arithmetics
    
    Make sure that the calculations we're doing on unsigned bytes can fit in
    the target variable by making it a 32-bit unsigned int.
    
    As detected by UBSan:
    io-ico.c:288:26: runtime error: left shift of 146 by 24 places cannot be
    represented in type 'int'
    io-ico.c:287:38: runtime error: left shift of 222 by 24 places cannot be
    represented in type 'int'
    
    https://bugzilla.gnome.org/show_bug.cgi?id=776040

 gdk-pixbuf/io-ico.c |   12 ++++++------
 1 files changed, 6 insertions(+), 6 deletions(-)
---
diff --git a/gdk-pixbuf/io-ico.c b/gdk-pixbuf/io-ico.c
index 9e5cce2..b7945de 100644
--- a/gdk-pixbuf/io-ico.c
+++ b/gdk-pixbuf/io-ico.c
@@ -131,7 +131,7 @@ struct ico_direntry_data {
        gint ImageScore;
         gint width;
         gint height;
-       gint DIBoffset;
+       guint DIBoffset;
        gint x_hot;
        gint y_hot;
 };
@@ -166,7 +166,7 @@ struct ico_progressive_state {
 
        struct headerpair Header;       /* Decoded (BE->CPU) header */
        GList *entries;
-       gint                    DIBoffset;
+       guint                   DIBoffset;
 
        GdkPixbuf *pixbuf;      /* Our "target" */
 };
@@ -284,16 +284,16 @@ static void DecodeHeader(guchar *Data, gint Bytes,
                 int depth;
                 int x_hot;
                 int y_hot;
-                int data_size G_GNUC_UNUSED;
-                int data_offset;
+                guint data_size G_GNUC_UNUSED;
+                guint data_offset;
 
                 width = Ptr[0];
                 height = Ptr[1];
                 depth = Ptr[2];
                x_hot = (Ptr[5] << 8) + Ptr[4];
                y_hot = (Ptr[7] << 8) + Ptr[6];
-                data_size = (Ptr[11] << 24) + (Ptr[10] << 16) + (Ptr[9] << 8) + (Ptr[8]);
-               data_offset = (Ptr[15] << 24) + (Ptr[14] << 16) + (Ptr[13] << 8) + (Ptr[12]);
+                data_size = ((guint) (Ptr[11]) << 24) + (Ptr[10] << 16) + (Ptr[9] << 8) + (Ptr[8]);
+               data_offset = ((guint) (Ptr[15]) << 24) + (Ptr[14] << 16) + (Ptr[13] << 8) + (Ptr[12]);
                 DEBUG(g_print ("Image %d: %d x %d\n\tDepth: %d\n", I, width, height, depth);
                 if (imgtype == 2)
                   g_print ("\tHotspot: %d x %d\n", x_hot, y_hot);