I've been annoyed by the fact that parse.y has a shift/reduce conflict.
It stems from the grammar for a function declaration:
function_def: WORD '(' ')' newline_list function_body
| FUNCTION WORD '(' ')' newline_list function_body
| FUNCTION WORD newline_list function_body
;
You can see the problem by running "bison --report=state -y -d
./parse.y" and looking at y.output. The difficulty being that when the
parser is standing here:
FUNCTION WORD '('
^
it can't tell whether it is before the () of the second alternative, or
it is before a function_body which is a "subshell" (a list of commands
in (...)), a version of the third alternative. In the latter case, the
parser has to generate an empty newline_list before it can consume the
'('.
It turns out that the solution is simple: Separate the third
alternative into two, one of which has no newline_list (the case of the
original 3rd alternative where newline_list is empty), and one in which
the newline_list is not empty:
function_def: WORD '(' ')' newline_list function_body
| FUNCTION WORD '(' ')' newline_list function_body
| FUNCTION WORD function_body
| FUNCTION WORD '\n' newline_list function_body
;
In the state that caused the conflict before, the parser no longer has
to decide whether to generate a newline_list, it can shift the '(' and
look at the following token before deciding what the situation is
(whether it is now inside a function_body or still working its way
through the function header).
I've appended the patch to fix this. In the patch, I also remove a
couple of empty lines that don't conform to the overall conventions of
the file.
Dale
----------------------------------------------------------------------
diff --git a/parse.y b/parse.y
index 3ff87bc..75b6957 100644
--- a/parse.y
+++ b/parse.y
@@ -926,12 +926,12 @@ case_command: CASE WORD newline_list IN newline_list
ESAC
function_def: WORD '(' ')' newline_list function_body
{ $$ = make_function_def ($1, $5, function_dstart,
function_bstart); }
-
| FUNCTION WORD '(' ')' newline_list function_body
{ $$ = make_function_def ($2, $6, function_dstart,
function_bstart); }
-
- | FUNCTION WORD newline_list function_body
- { $$ = make_function_def ($2, $4, function_dstart,
function_bstart); }
+ | FUNCTION WORD function_body
+ { $$ = make_function_def ($2, $3, function_dstart,
function_bstart); }
+ | FUNCTION WORD '\n' newline_list function_body
+ { $$ = make_function_def ($2, $5, function_dstart,
function_bstart); }
;
function_body: shell_command
[END]
