Issue 260413.1: Wrong form classes for DW_CFA_def_cfa_expression, _expression, and _val_expression
| Author: | Cary Coutant |
|---|---|
| Champion: | |
| Date submitted: | 2026-04-13 |
| Date revised: | 2026-04-22 |
| Date closed: | 2026-04-27 |
| Type: | Error |
| Status: | Accepted |
| DWARF version: | 6 |
After accepting Issue 230616.1, we made the following editorial changes (among others):
- Section 6.4.2.2, p. 178, bullet 6, line 27 [
DW_CFA_def_cfa_expression]: exprloc -> exprval. - Section 6.4.2.3, p. 180, bullet 9, line 13 [
DW_CFA_expression]:DW_FORM_block-> exprloc -> exprval. - Section 6.4.2.3, p. 180, bullet 10, line 21 [
DW_CFA_val_expression]:DW_FORM_block-> exprloc -> exprval.
Note that Section 6.4 is now 7.4. The page numbers are now closer to 200 and 202.
Also, as a result of 251030.1, the form classes were renamed valexpr and locexpr.
It seems to me that the first two, DW_CFA_def_cfa_expression and
DW_CFA_expression, should be locexpr, not valexpr. These are
expressions that return a location, not a value. That's the
difference between DW_CFA_expression and DW_CFA_val_expression:
the first gives a location, and second gives a value.
In Section 8.23, Table 8.29 has DW_CFA_def_cfa_expression and
DW_CFA_expression taking locexpr (correct, I think), but also
lists DW_CFA_val_expression as taking locexpr (wrong, should be
valexpr).
Proposal
In Section 7.4.2.2 CFA Definition Instructions, bullet 6,
DW_CFA_def_cfa_expression, change "valexpr" to "locexpr".
In Section 7.4.2.3 Register Rule Instructions, bullet 9,
DW_CFA_expression, change "valexpr" to "locexpr".
(Bullet 10, DW_CFA_val_expression is correct.)
In Section 8.23 Call Frame Information, Table 8.29,
in the row for DW_CFA_val_expression, change "locexpr" to "valexpr".
(The rows for DW_CFA_def_cfa_expression and DW_CFA_expression are correct.)
2026-04-27: Accepted.
