[bdf] Fix underflow of an unsigned value.

bdflib.c:1562 could be reached with `font->glyphs_used == 0'.  That
caused an underflow of the unsigned value which results in undefined
behaviour.

* src/bdf/bdflib.c (src/bdf/bdflib.c): Bail out earlier than before
if the `ENCODING' keyword cannot be found.

ChangeLog

@@ -1,3 +1,14 @@
+2018-06-17  Armin Hasitzka  <prince.cherusker@gmail.com>
+
+	[bdf] Fix underflow of an unsigned value.
+
+	bdflib.c:1562 could be reached with `font->glyphs_used == 0'.  That
+	caused an underflow of the unsigned value which results in undefined
+	behaviour.
+
+	* src/bdf/bdflib.c (src/bdf/bdflib.c): Bail out earlier than before
+	if the `ENCODING' keyword cannot be found.
+
 2018-06-17  Werner Lemberg  <wl@gnu.org>
 
 	[base] Add tracing for `FT_Bitmap_Blend'.

src/bdf/bdflib.c

@@ -1556,6 +1556,9 @@
       goto Exit;
     }
 
+    if ( !( p->flags & BDF_ENCODING_ ) )
+      goto Missing_Encoding;
+
     /* Point at the glyph being constructed. */
     if ( p->glyph_enc == -1 )
       glyph = font->unencoded + ( font->unencoded_used - 1 );
@@ -1626,9 +1629,6 @@
     /* Expect the SWIDTH (scalable width) field next. */
     if ( _bdf_strncmp( line, "SWIDTH", 6 ) == 0 )
     {
-      if ( !( p->flags & BDF_ENCODING_ ) )
-        goto Missing_Encoding;
-
       error = _bdf_list_split( &p->list, (char *)" +", line, linelen );
       if ( error )
         goto Exit;
@@ -1642,9 +1642,6 @@
     /* Expect the DWIDTH (scalable width) field next. */
     if ( _bdf_strncmp( line, "DWIDTH", 6 ) == 0 )
     {
-      if ( !( p->flags & BDF_ENCODING_ ) )
-        goto Missing_Encoding;
-
       error = _bdf_list_split( &p->list, (char *)" +", line, linelen );
       if ( error )
         goto Exit;
@@ -1670,9 +1667,6 @@
     /* Expect the BBX field next. */
     if ( _bdf_strncmp( line, "BBX", 3 ) == 0 )
     {
-      if ( !( p->flags & BDF_ENCODING_ ) )
-        goto Missing_Encoding;
-
       error = _bdf_list_split( &p->list, (char *)" +", line, linelen );
       if ( error )
         goto Exit;