mailing-list for TeXmacs Users

[Enrique Perez-Terron <address@hidden>]

I have had a look at the source code. Widgets are ref-counted, and
automatically deleted when the refcount comes down to zero.

Setting a breakpoint in the destructor for edit_interface_rep, I found
the refcount was zero. However, when if calls is_attached(this) a new
reference is created, and when this reference is deleted as it goes out
of scope, the reference count goes to zero again. This initiates a
second call to the destructor for the same object.

The reference is created because is_attached() is declared to take a
'widget' object, ie a reference-counting pointer. The 'this' pointer is
just a pointer, but the compiler constructs a temporary 'widget' object.

I tried to add a boolean "is_dying" to the base class holding the
reference counter, and an additional condition before deleting, so it
only deletes if the refcount becomes zero and is_dying is false. 

Then texmacs does not crash.
--- texmacs-1.0.6.14/src/Kernel/Abstractions/basic.hpp  2008-03-19
18:16:36.000000000 +0100
+++ texmacs-new/src/Kernel/Abstractions/basic.hpp       2008-10-03
04:41:13.000000000 +0200
@@ -105,14 +105,16 @@
 extern int concrete_count;
 struct concrete_struct {
   int ref_count;
-  inline concrete_struct (): ref_count (1) { DEBUG(concrete_count++); }
+  bool deleting;
+  inline concrete_struct (): ref_count (1), deleting(false)
{ DEBUG(concrete_count++); }
   virtual inline ~concrete_struct () { DEBUG(concrete_count--); }
 };
 
 extern int abstract_count;
 struct abstract_struct {
   int ref_count;
-  inline abstract_struct (): ref_count (0) { DEBUG(abstract_count++); }
+  bool deleting;
+  inline abstract_struct (): ref_count (0), deleting(false)
{ DEBUG(abstract_count++); }
   virtual inline ~abstract_struct () { DEBUG(abstract_count--); }
 };
 
@@ -131,9 +133,10 @@

******************************************************************************/
 
 #define INC_COUNT(R)      { (R)->ref_count++; }
-#define DEC_COUNT(R)      { if(0==--((R)->ref_count)) delete (R); }
+#define DEC_COUNT(R)      { if(!(R)->deleting && 0==--((R)->ref_count))
\
+      {(R)->deleting = true; delete (R);} }
 #define INC_COUNT_NULL(R) { if ((R)!=NULL) (R)->ref_count++; }
-#define DEC_COUNT_NULL(R) { if ((R)!=NULL && 0==--((R)->ref_count))
delete (R); }
+#define DEC_COUNT_NULL(R) { if ((R)!=NULL) DEC_COUNT(R); }
 
 // concrete
 #define CONCRETE(PTR)               \