Re: Bison 3.0: semantic predicates are mis-scanned as invalid directives

[Akim Demaille]

[resent to be public]

Le 16 oct. 2013 à 15:39, Rici Lake <address@hidden> a écrit :

> Hi, Akim.
> 
> I really think my fix is better. Rearranging the patterns will still allow 
> the error pattern to win if it is longer, such as:
> 
>   %?{safe_mode}
> 
> I don't believe there is a requirement that { be followed by a space, even if 
> most of us would do that.

You do have a point, thanks for catching this!  However, really,
I do not want

 exp?: exp{ "+" exp{

to become valid: "?" and "{" are _not_ letters.

Well, I think I tried too hard to have nice messages for unexpected
"%" combinations, such as "%'" or whatever, but it's simpler and
safer to leave the code do its jobs as it did before.

The catch-all case will handle such errors.

$ cat /tmp/foo.yy
%!
%%
exp:
$ LC_ALL=C ./_build/48s/tests/bison /tmp/foo.yy
/tmp/foo.yy:1.1: error: invalid character: '%'
%!
^
/tmp/foo.yy:1.2: error: invalid character: '!'
%!
 ^

Here's the second version of patch (until you come with another bug
report :).

commit 071863b3d88c232c10348b7c38378c47d363857c
Author: Akim Demaille <address@hidden>
Date:   Wed Oct 16 15:19:44 2013 +0200

   glr: allow spaces between "%?" and "{" in predicates

   Reported by Rici Lake.
   http://lists.gnu.org/archive/html/bug-bison/2013-10/msg00004.html
   http://stackoverflow.com/questions/19330171/

   * src/scan-gram.l: Do not try to be too smart when diagnosing invalid
   directives.
   * tests/glr-regression.at (Predicates): New test.

diff --git a/NEWS b/NEWS
index 7a2d4b5..e01198d 100644
--- a/NEWS
+++ b/NEWS
@@ -15,6 +15,11 @@ GNU Bison NEWS
  leaves "foo" diagnostics as warnings.  Similarly, with "-Werror=foo
  -Wno-error", "foo" diagnostics are now errors.

+*** GLR Predicates
+
+  As demonstrated in the documentation, one can now leave spaces between
+  "%?" and its "{".
+
* Noteworthy changes in release 3.0 (2013-07-25) [stable]

** WARNING: Future backward-incompatibilities!
diff --git a/THANKS b/THANKS
index 2d4a6a9..0ffa8b6 100644
--- a/THANKS
+++ b/THANKS
@@ -110,6 +110,7 @@ R Blake                   address@hidden
Raja R Harinath           address@hidden
Ralf Wildenhues           address@hidden
Richard Stallman          address@hidden
+Rici Lake                 address@hidden
Rob Vermaas               address@hidden
Robert Anisko             address@hidden
Rob Conde                 address@hidden
diff --git a/src/scan-gram.l b/src/scan-gram.l
index 665e80d..555e695 100644
--- a/src/scan-gram.l
+++ b/src/scan-gram.l
@@ -266,7 +266,7 @@ eqopt    ([[:space:]]*=)?
  "%pure"[-_]"parser"               DEPRECATED("%pure-parser");
  "%token"[-_]"table"               DEPRECATED("%token-table");

-  "%"{id}|"%"{notletter}([[:graph:]])+ {
+  "%"{id} {
    complain (loc, complaint, _("invalid directive: %s"), quote (yytext));
  }

diff --git a/tests/glr-regression.at b/tests/glr-regression.at
index 711ab7e..064b37b 100644
--- a/tests/glr-regression.at
+++ b/tests/glr-regression.at
@@ -1749,3 +1749,33 @@ Cleanup: popping token 'a' ()
])

AT_CLEANUP
+
+
+## ----------------------------------------------------------------- ##
+## Predicates.                                                       ##
+##                                                                   ##
+## http://lists.gnu.org/archive/html/bug-bison/2013-10/msg00004.html ##
+## ----------------------------------------------------------------- ##
+
+AT_SETUP([Predicates])
+
+# FIXME: We need genuine test cases with uses of %?.
+
+AT_DATA_GRAMMAR([input.y],
+[[%glr-parser
+%expect-rr 1
+%%
+// Exercise "%?{...}" and "%? {...}".
+widget:
+  %? {new_syntax} "widget" id new_args  { $$ = f($3, $4); }
+| %?{!new_syntax} "widget" id old_args  { $$ = f($3, $4); }
+;
+id:;
+new_args:;
+old_args:;
+%%
+]])
+
+AT_BISON_CHECK([[input.y]])
+
+AT_CLEANUP