VM: try and recover with a kernel error from the callback heap running out

basis/debugger/debugger.factor

@@ -148,6 +148,9 @@ HOOK: signal-error. os ( obj -- )
 : interrupt-error. ( error -- )
     "Interrupt" print drop ;
 
+: callback-space-overflow. ( error -- )
+    "Callback space overflow" print drop ;
+
 PREDICATE: vm-error < array
     dup length 2 < [ drop f ] [
         {
@@ -178,6 +181,7 @@ PREDICATE: vm-error < array
         [ memory-error.            ]
         [ fp-trap-error.           ]
         [ interrupt-error.         ]
+        [ callback-space-overflow. ]
     } ; inline
 
 M: vm-error summary drop "VM error" ;

core/kernel/kernel.factor

@@ -352,6 +352,8 @@ CONSTANT: OBJ-WAITING-CALLBACKS 73
 
 CONSTANT: OBJ-SIGNAL-PIPE 74
 
+CONSTANT: OBJ-INSTALL-PREFIX 75
+
 ! Context object count and identifiers must be kept in sync with:
 !   vm/contexts.hpp
 
@@ -363,9 +365,10 @@ CONSTANT: CONTEXT-OBJ-CONTEXT 2
 CONSTANT: CONTEXT-OBJ-IN-CALLBACK-P 3
 
 ! Runtime errors must be kept in sync with:
+!   basis/debugger/debugger.factor
 !   vm/errors.hpp
 
-CONSTANT: kernel-error-count 20
+CONSTANT: kernel-error-count 21
 
 CONSTANT: ERROR-EXPIRED 0
 CONSTANT: ERROR-IO      1
@@ -387,5 +390,6 @@ CONSTANT: ERROR-CALLSTACK-OVERFLOW 16
 CONSTANT: ERROR-MEMORY 17
 CONSTANT: ERROR-FP-TRAP 18
 CONSTANT: ERROR-INTERRUPT 19
+CONSTANT: ERROR-CALLBACK-SPACE-OVERFLOW 20
 
 PRIVATE>

vm/callbacks.cpp

@@ -61,8 +61,12 @@ code_block* callback_heap::add(cell owner, cell return_rewind) {
   cell size = array_capacity(insns.untagged());
 
   cell bump = align(size + sizeof(code_block), data_alignment);
-  if (here + bump > seg->end)
-    fatal_error("Out of callback space", 0);
+
+  if (here + bump > seg->end) {
+    parent->general_error(ERROR_CALLBACK_SPACE_OVERFLOW,
+                          false_object,
+                          false_object);
+  }
 
   free_heap_block* free_block = (free_heap_block*)here;
   free_block->make_free(bump);

vm/errors.hpp

@@ -24,6 +24,7 @@ enum vm_error_type {
   ERROR_MEMORY,
   ERROR_FP_TRAP,
   ERROR_INTERRUPT,
+  ERROR_CALLBACK_SPACE_OVERFLOW
 };
 
 void fatal_error(const char* msg, cell tagged);