[gegl] buffer: allow disabling tile allocator through GEGL_TILE_ALLOC env var

[Ell <ell src gnome org>]

commit bd4caacaa1fef5c6d8ec8efa0ea0e5150ff8b3b3
Author: Ell <ell_se yahoo com>
Date:   Sun Apr 26 11:18:35 2020 +0300

    buffer: allow disabling tile allocator through GEGL_TILE_ALLOC env var
    
    In gegl-tile-alloc, allow disabling the tile allocator, and using
    plaing gegl_malloc() for tiles instead, by setting the
    GEGL_TILE_ALLOC environment variable to 0.  This is useful for
    troubleshooting.

 gegl/buffer/gegl-tile-alloc.c | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)
---
diff --git a/gegl/buffer/gegl-tile-alloc.c b/gegl/buffer/gegl-tile-alloc.c
index 5745bec9c..c7cf44ec3 100644
--- a/gegl/buffer/gegl-tile-alloc.c
+++ b/gegl/buffer/gegl-tile-alloc.c
@@ -19,6 +19,7 @@
 #include "config.h"
 
 #include <math.h>
+#include <stdlib.h>
 #include <string.h>
 
 #ifdef HAVE_MALLOC_TRIM
@@ -256,6 +257,22 @@ gegl_tile_alloc_fallback (gsize size)
   return gegl_tile_buffer_to_data (buffer);
 }
 
+static gboolean
+gegl_tile_alloc_enabled (void)
+{
+  static gint enabled = -1;
+
+  if (enabled < 0)
+    {
+      if (g_getenv ("GEGL_TILE_ALLOC"))
+        enabled = atoi (g_getenv ("GEGL_TILE_ALLOC")) ? TRUE : FALSE;
+      else
+        enabled = TRUE;
+    }
+
+  return enabled;
+}
+
 
 /*  public functions  */
 
@@ -270,7 +287,7 @@ gegl_tile_alloc (gsize size)
   gint                       i;
   gint                       j;
 
-  if (size > GEGL_TILE_MAX_SIZE)
+  if (size > GEGL_TILE_MAX_SIZE || ! gegl_tile_alloc_enabled ())
     return gegl_tile_alloc_fallback (size);
 
   size = MAX (size, GEGL_TILE_MIN_SIZE);