Normative ERRNO code table

The integer value of ERRNO after a documented failure is normative per the Autodesk "Error Codes Reference (AutoLISP)" table. The table was first published in the AutoCAD 2015 ENU AutoLISP help (GUID 97327347-2A13-4CBC-BDBF-979C7F1CABD5) and has remained stable in later releases (Autodesk no longer publishes a standalone code-list page in the 2026 cloudhelp index, but the per-function pages still reference these codes by number).

Code	Meaning
0	No error / success
1	Invalid symbol-table name
2	Invalid entity or selection-set name
3	Exceeded maximum number of selection sets
4	Invalid selection set
5	Improper use of block definition
6	Improper use of xref
7	Object selection: pick failed
8	End of entity file
9	End of block definition file
10	Failed to find last entity
11	Illegal attempt to delete viewport object
12	Operation not allowed during PLINE
13	Invalid handle
14	Handles not enabled
15	Invalid arguments in coordinate transform request
16	Invalid space in coordinate transform request
17	Invalid use of deleted entity
18	Invalid table name
19	Invalid table function argument
20	Attempt to set a read-only variable
21	Zero value not allowed
22	Value out of range
23	Complex REGEN in progress
24	Attempt to change entity type
25	Bad layer name
26	Bad linetype name
27	Bad color name
28	Bad text style name
29	Bad shape name
30	Bad field for entity type
31	Attempt to modify deleted entity
32	Attempt to modify seqend subentity
33	Attempt to change handle
34	Attempt to modify viewport visibility
35	Entity on locked layer
36	Bad entity type
37	Bad polyline entity
38	Incomplete complex entity in block
39	Invalid block name field
40	Duplicate block flag fields
41	Duplicate block name fields
42	Bad normal vector
43	Missing block name
44	Missing block flags
45	Invalid anonymous block
46	Invalid block definition
47	Mandatory field missing
48	Unrecognized extended data (XDATA) type
49	Improper nesting of list in XDATA
50	Improper location of APPID field
51	Exceeded maximum XDATA size
52	Entity selection: null response
53	Duplicate APPID
54	Attempt to make or modify viewport entity
55	Attempt to make or modify an xref, xdef, or xdep
56	ssget filter: unexpected end of list
57	ssget filter: missing test operand
58	ssget filter: invalid opcode (-4) string
59	ssget filter: improper nesting or empty conditional clause
60	ssget filter: mismatched begin and end of conditional clause
61	ssget filter: wrong number of arguments in conditional
62	ssget filter: exceeded maximum nesting limit
63	ssget filter: invalid group code
64	ssget filter: invalid string test
65	ssget filter: invalid vector test
66	ssget filter: invalid real test
67	ssget filter: invalid integer test
68	Digitizer is not a tablet
69	Tablet is not calibrated
70	Invalid tablet arguments
71	ADS error: unable to allocate new result buffer
72	ADS error: null pointer detected
73	Cannot open executable file
74	Application is already loaded
75	Maximum number of applications already loaded
76	Unable to execute application
77	Incompatible version number
78	Unable to unload nested application
79	Application refused to unload
80	Application is not currently loaded
81	Not enough memory to load application
82	ADS error: invalid transformation matrix
83	ADS error: invalid symbol name
84	ADS error: invalid symbol value
85	AutoLISP/ADS operation prohibited while a dialog box

Per Autodesk's note attached to the ERRNO sysvar entry, "ERRNO is not always cleared to zero. Unless it is inspected immediately after an AutoLISP function has reported an error, the error that its value indicates may be misleading." ERRNO is reset to 0 on the success path of every builtin that documents itself as "sets ERRNO on failure"; an arbitrary other-builtin success leaves the previous value in place.

The host implementation in clautolisp/autolisp-builtins-core wires the matching set-autolisp-errno calls into the builtins that Autodesk documents in the ERRNO sysvar entry's coupling list (entget, entmake, entmod, entsel, findfile, load, nentsel, open, read-line, ssget, ssname, tablet, write-line, xdsize). Builtins outside that list – including the entdel / entupd / entlast / entnext family – do not touch ERRNO because Autodesk's documentation does not specify a behaviour for them.