#4471: bison-3.4
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Reporter: bdubbs | Owner: lfs-book
Type: task | Status: new
Priority: normal | Milestone: 8.5
Component: Book | Version: SVN
Severity: normal | Resolution:
Keywords: |
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Comment (by bdubbs):
Noteworthy changes in release 3.4.1 (2019-05-22) [stable]
- Portability fixes.
Noteworthy changes in release 3.4 (2019-05-19) [stable]
* Deprecated features
The %pure-parser directive is deprecated in favor of '%define api.pure'
since Bison 2.3b (2008-05-27), but no warning was issued; there is one
now. Note that since Bison 2.7 you are strongly encouraged to use
'%define api.pure full' instead of '%define api.pure'.
* New features
* Colored diagnostics
As an experimental feature, diagnostics are now colored, controlled by
the
new options --color and --style.
To use them, install the libtextstyle library before configuring Bison.
It is available from
https://alpha.gnu.org/gnu/gettext/
for instance
https://alpha.gnu.org/gnu/gettext/libtextstyle-0.8.tar.gz
The option --color supports the following arguments:
- always, yes: Enable colors.
- never, no: Disable colors.
- auto, tty (default): Enable colors if the output device is a tty.
To customize the styles, create a CSS file similar to
/* bison-bw.css */
.warning { }
.error { font-weight: 800; text-decoration: underline; }
.note { }
then invoke bison with --style=bison-bw.css, or set the BISON_STYLE
environment variable to "bison-bw.css".
* Disabling output
When given -fsyntax-only, the diagnostics are reported, but no output is
generated.
The name of this option is somewhat misleading as bison does more than
just checking the syntax: every stage is run (including checking for
conflicts for instance), except the generation of the output files.
* Include the generated header (yacc.c)
Before, when --defines is used, bison generated a header, and pasted an
exact copy of it into the generated parser implementation file. If the
header name is not "y.tab.h", it is now #included instead of being
duplicated.
To use an '#include' even if the header name is "y.tab.h" (which is what
happens with --yacc, or when using the Autotools' ylwrap), define
api.header.include to the exact argument to pass to #include. For
instance:
%define api.header.include {"parse.h"}
or
%define api.header.include {<parser/parse.h>}
* api.location.type is now supported in C (yacc.c, glr.c)
The %define variable api.location.type defines the name of the type to
use
for locations. When defined, Bison no longer defines YYLTYPE.
This can be used in programs with several parsers to factor their
definition of locations: let one of them generate them, and the others
just use them.
* Changes
* Graphviz output
In conformance with the recommendations of the Graphviz team, if
%require
"3.4" (or better) is specified, the option --graph generates a *.gv file
by default, instead of *.dot.
* Diagnostics overhaul
Column numbers were wrong with multibyte characters, which would also
result in skewed diagnostics with carets. Beside, because we were
indenting the quoted source with a single space, lines with tab
characters
were incorrectly underlined.
To address these issues, and to be clearer, Bison now issues diagnostics
as GCC9 does. For instance it used to display (there's a tab before the
opening brace):
foo.y:3.37-38: error: $2 of ‘expr’ has no declared type
expr: expr '+' "number" { $$ = $1 + $2; }
^~
It now reports
foo.y:3.37-38: error: $2 of ‘expr’ has no declared type
3 | expr: expr '+' "number" { $$ = $1 + $2; }
| ^~
Other constructs now also have better locations, resulting in more
precise
diagnostics.
* Fix-it hints for %empty
Running Bison with -Wempty-rules and --update will remove incorrect
%empty
annotations, and add the missing ones.
* Generated reports
The format of the reports (parse.output) was improved for readability.
* Better support for --no-line.
When --no-line is used, the generated files are now cleaner: no lines
are
generated instead of empty lines. Together with using
api.header.include,
that should help people saving the generated files into version control
systems get smaller diffs.
* Documentation
A new example in C shows an simple infix calculator with a hand-written
scanner (examples/c/calc).
A new example in C shows a reentrant parser (capable of recursive calls)
built with Flex and Bison (examples/c/reccalc).
There is a new section about the history of Yaccs and Bison.
* Bug fixes
A few obscure bugs were fixed, including the second oldest (known) bug
in
Bison: it was there when Bison was entered in the RCS version control
system, in December 1987. See the NEWS of Bison 3.3 for the previous
oldest bug.
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