Add extra assert() statements trying to catch a Mem object in an inconsistent

state.

FossilOrigin-Name: 4aeb3ae435c78070232fef21a147fde4e1c5cd31

src/vdbeInt.h

@@ -232,6 +232,24 @@ struct Mem {
 #define memIsValid(M)  ((M)->flags & MEM_Undefined)==0
 #endif
 
+/*
+** A sanity check on a Mem object and especially the Mem.z field.
+** This check says that no more than one of the following may be true:
+**   (1) Mem.z comes from Mem.zMalloc
+**   (2) Mem.z has a destructor Mem.xDel
+**   (3) Mem.z is an ephemeral string
+**   (4) Mem.z is a static string
+**
+** Use only inside of an assert() as follows:  assert( memSanify(pMem) );
+*/
+#ifdef SQLITE_DEBUG
+#define memSanity1(p)                                  \
+   ((((p)->zMalloc && (p)->zMalloc==(p)->z) ? 1 : 0) + \
+    ((((p)->flags&MEM_Dyn)&&(p)->xDel) ? 1 : 0) +      \
+    (((p)->flags&MEM_Ephem) ? 1 : 0) +                 \
+    (((p)->flags&MEM_Static) ? 1 : 0) <= 1 )
+#endif
+
 /*
 ** Each auxilliary data pointer stored by a user defined function 
 ** implementation calling sqlite3_set_auxdata() is stored in an instance