fix #H5780 - file pointer freed twice

win/share/tileset.c seems only to be used by the MSDOS port, but it
compiles cleanly on OSX after these changes.

A file pointer was passed to fclose() twice, second time potentially
causing problems.  There were cases of potentially null pointers
being passed to free() too.  That should be safe these days, but it's
something we've tried to hard to avoid and would probably trigger
complaints from our own MONITOR_HEAP code if that ever got applied
here.

win/share/tileset.c

@@ -1,4 +1,4 @@
-/* NetHack 3.6    tileset.c    $NHDT-Date: 1457207053 2016/03/05 19:44:13 $ $NHDT-Branch: chasonr $:$NHDT-Revision: 1.0 $ */
+/* NetHack 3.6    tileset.c    $NHDT-Date: 1501463811 2017/07/31 01:16:51 $ $NHDT-Branch: NetHack-3.6.0 $:$NHDT-Revision: 1.0 $ */
 /* Copyright (c) Ray Chason, 2016. */
 /* NetHack may be freely redistributed.  See license for details. */
 
@@ -25,7 +25,7 @@ boolean true_color;
         0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A
     };
     struct TileSetImage image;
-    FILE *fp = NULL;            /* custodial */
+    FILE *fp;
     char header[16];
     boolean ok;
 
@@ -40,10 +40,11 @@ boolean true_color;
 
     /* Identify the image type */
     fp = fopen(filename, "rb");
-    if (fp == NULL) goto error;
+    if (!fp)
+        goto error;
     memset(header, 0, sizeof(header));
     fread(header, 1, sizeof(header), fp);
-    fclose(fp);
+    fclose(fp), fp = (FILE *) 0;
 
     /* Call the loader appropriate for the image */
     if (memcmp(header, "BM", 2) == 0) {
@@ -56,11 +57,13 @@ boolean true_color;
     } else {
         ok = FALSE;
     }
-    if (!ok) goto error;
+    if (!ok)
+        goto error;
 
     /* Reject if the interface cannot handle direct color and the image does
        not use a palette */
-    if (!true_color && image.indexes == NULL) goto error;
+    if (!true_color && image.indexes == NULL)
+        goto error;
 
     /* Save the palette if present */
     have_palette = image.indexes != NULL;
@@ -87,12 +90,12 @@ boolean true_color;
     /* Split the image into tiles */
     split_tiles(&image);
 
-    fclose(fp);
     free_image(&image);
     return TRUE;
 
 error:
-    if (fp) fclose(fp);
+    if (fp)
+        fclose(fp);
     free_image(&image);
     return FALSE;
 }
@@ -108,6 +111,7 @@ static void
 get_tile_map(image_desc)
 const char *image_desc;
 {
+    return;
 }
 
 void
@@ -115,43 +119,40 @@ free_tiles()
 {
     unsigned i;
 
-    if (tiles != NULL) {
+    if (tiles) {
         for (i = 0; i < num_tiles; ++i) {
-            free(tiles[i].pixels);
+            free((genericptr_t) tiles[i].pixels);
-            free(tiles[i].indexes);
+            free((genericptr_t) tiles[i].indexes);
         }
+        free((genericptr_t) tiles), tiles = NULL;
     }
-    free(tiles);
-    tiles = NULL;
     num_tiles = 0;
 
-    free(blank_tile.pixels);
+    if (blank_tile.pixels)
-    blank_tile.pixels = NULL;
+        free((genericptr_t) blank_tile.pixels), blank_tile.pixels = NULL;
-    free(blank_tile.indexes);
+    if (blank_tile.indexes)
-    blank_tile.indexes = NULL;
+        free((genericptr_t) blank_tile.indexes), blank_tile.indexes = NULL;
 }
 
 static void
 free_image(image)
 struct TileSetImage *image;
 {
-    free(image->pixels);
+    if (image->pixels)
-    image->pixels = NULL;
+        free((genericptr_t) image->pixels), image->pixels = NULL;
-    free(image->indexes);
+    if (image->indexes)
-    image->indexes = NULL;
+        free((genericptr_t) image->indexes), image->indexes = NULL;
-    free(image->image_desc);
+    if (image->image_desc)
-    image->image_desc = NULL;
+        free((genericptr_t) image->image_desc), image->image_desc = NULL;
 }
 
 const struct TileImage *
 get_tile(tile_index)
 unsigned tile_index;
 {
-    if (tile_index >= num_tiles) {
+    if (tile_index >= num_tiles)
         return &blank_tile;
-    } else {
+    return &tiles[tile_index];
-        return &tiles[tile_index];
-    }
 }
 
 static void
@@ -176,10 +177,11 @@ const struct TileSetImage *image;
     for (y1 = 0; y1 < tile_rows; ++y1) {
         for (x1 = 0; x1 < tile_cols; ++x1) {
             struct TileImage *tile = &tiles[y1 * tile_cols + x1];
+
             tile->width = iflags.wc_tile_width;
             tile->height = iflags.wc_tile_height;
             tile->pixels = (struct Pixel *)
-                    alloc(tile_size * sizeof(struct Pixel));
+                    alloc(tile_size * sizeof (struct Pixel));
             if (image->indexes != NULL) {
                 tile->indexes = (unsigned char *) alloc(tile_size);
             }
@@ -187,6 +189,7 @@ const struct TileSetImage *image;
                 for (x2 = 0; x2 < iflags.wc_tile_width; ++x2) {
                     unsigned x = x1 * iflags.wc_tile_width + x2;
                     unsigned y = y1 * iflags.wc_tile_height + y2;
+
                     i = y * image->width + x;
                     j = y2 * tile->width + x2;
                     tile->pixels[j] = image->pixels[i];
@@ -202,7 +205,7 @@ const struct TileSetImage *image;
     blank_tile.width = iflags.wc_tile_width;
     blank_tile.height = iflags.wc_tile_height;
     blank_tile.pixels = (struct Pixel *)
-            alloc(tile_size * sizeof(struct Pixel));
+            alloc(tile_size * sizeof (struct Pixel));
     for (i = 0; i < tile_size; ++i) {
         blank_tile.pixels[i].r = 0;
         blank_tile.pixels[i].g = 0;