do not assign clones to objects on the pari stack

cypari2/gen.pyx

@@ -1531,6 +1531,11 @@ cdef class Gen(Gen_base):
 
             self.cache((i,j), x)
             xt = x.ref_target()
+
+            if not is_universal_constant(x.g):
+                # Make sure that self is on the heap, before we assign a clone to it.
+                self.fixGEN()
+
             set_gcoeff(self.g, i+1, j+1, xt)
             return
 
@@ -1555,6 +1560,10 @@ cdef class Gen(Gen_base):
 
         self.cache(i, x)
         xt = x.ref_target()
+        if not is_universal_constant(x.g):
+            # Make sure that self is on the heap, before we assign a clone to it.
+            self.fixGEN()
+
         if typ(self.g) == t_LIST:
             listput(self.g, xt, i+1)
         else:

cypari2/pari_instance.pyx

@@ -1298,6 +1298,10 @@ cdef class Pari(Pari_auto):
             if len(entries) != m * n:
                 raise IndexError("len of entries (=%s) must be %s*%s=%s"%(len(entries),m,n,m*n))
             k = 0
+
+            # Make sure that A is on the heap, before we assign clones to it.
+            A.fixGEN()
+
             for i in range(m):
                 for j in range(n):
                     sig_check()
@@ -1318,7 +1322,7 @@ cdef class Pari(Pari_auto):
 
         If the second argument `p` is specified, it must be a prime.
         Then only the local information at `p` is computed and returned.
-        
+
         Examples:
 
         >>> import cypari2