graphics library - improve gx_cpath_copy

This function does not, currently, appear to be called from anywhere.
For the new PDF interpreter we'd like to use it to copy the clip path(s)
from the PostScript environment to the PDF environment, but there's a
problem.

The problem is that the structures defining the list of rectangles are
allocated using the same memory allocator as the source clip path, but
when we come to free them, the destructor uses the memory allocator of
the clip list. So if the destination clip path was using a different
allocator from the source clip path, we will use the wrong allocator to
try and free the memory.

Chris thinks this may be an attempt to cope with stack-based allocations
of the clip path where the allocator is NULL. So to cope with that
we use the existing code (allocator from the source clip path) if the
destination clip path's allocator is NULL (stack based) and we use the
destination clip path's allocator otherwise.

1 files changed, 5 insertions, 1 deletions

diff --git a/base/gxcpath.c b/base/gxcpath.c
index 082c3890b..c9fde9d49 100644
--- a/base/gxcpath.c
+++ b/base/gxcpath.c
@@ -1122,7 +1122,11 @@ gx_cpath_copy(const gx_clip_path * from, gx_clip_path * pcpath)
     pcpath->cached = NULL;
     l->single = from->rect_list->list.single;
     for (r = from->rect_list->list.head; r != NULL; r = r->next) {
-        s = gs_alloc_struct(from->rect_list->rc.memory, gx_clip_rect, &st_clip_rect, "gx_cpath_copy");
+        if (pcpath->rect_list->rc.memory == NULL)
+            s = gs_alloc_struct(from->rect_list->rc.memory, gx_clip_rect, &st_clip_rect, "gx_cpath_copy");
+        else
+            s = gs_alloc_struct(pcpath->rect_list->rc.memory, gx_clip_rect, &st_clip_rect, "gx_cpath_copy");
+
         if (s == NULL)
             return_error(gs_error_VMerror);
         *s = *r;