revise set_blob types

jcupitt · jcupitt · commit 6ed388bccf19 · 2020-04-10T12:58:50.000+01:00
We were seeing exceptions with older libvipses because ffi throws an
exception on type error in ABI mode.

Instead, move the type fudging to C, so we just get a compile-time
warning in API mode.
diff --git a/CHANGELOG.rst b/CHANGELOG.rst
@@ -5,6 +5,7 @@
 * update enums.py [tony612]
 * add gen-enums.py [jcupitt]
 * improve custom source/target types [jcupitt]
+* revise types for set_blob [jcupitt]
 
 ## Version 2.1.11 (7 Nov 2019) 
 
diff --git a/pyvips/gvalue.py b/pyvips/gvalue.py
@@ -221,6 +221,9 @@ def set(self, value):
                 vips_lib.vips_value_set_blob_free(self.gvalue,
                                                   memory, len(value))
             else:
+                # we declare the type of the free func in set_blob incorrectly
+                # so that we can pass g_free at runtime without triggering an
+                # exception
                 if pyvips.API_mode:
                     vips_lib.vips_value_set_blob(self.gvalue,
                                                  ffi.NULL, memory, len(value))
diff --git a/pyvips/vdecls.py b/pyvips/vdecls.py
@@ -107,9 +107,9 @@ def cdefs(features):
         void vips_value_set_array_int (GValue* value,
             const int* array, int n );
         void vips_value_set_array_image (GValue *value, int n);
-        typedef int (*VipsCallbackFn)(void* a, void* b);
+        typedef void (*FreeFn)(void* a);
         void vips_value_set_blob (GValue* value,
-            VipsCallbackFn free_fn, void* data, size_t length);
+            FreeFn free_fn, void* data, size_t length);
 
         bool g_value_get_boolean (const GValue* value);
         int g_value_get_int (GValue* value);
