Re: #line directives are incorrectly inserted in the middle of a line in semantic predicate tests.

[Akim Demaille]

Hi!

> Le 28 mai 2018 à 07:23, Rici Lake <address@hidden> a écrit :
> 
> Version: 3.04 (also fails on 3.01 and 3.02)
> Platform: Linux but I think it would be the same on any platform
> 
> To reproduce, it is possible to use the semantic predicate test snippet
> already in the bison test suite:
> 
> %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:;
> %%
> 
> produces (at line 789):
> 
>       case 2:
>   if (! (#line 6 "sempred.y" /* glr.c:816  */
>   new_syntax)) YYERROR;
> #line 793 "sempred.tab.c" /* glr.c:816  */
>   break;
> 
> which of course produces a compiler error.
> 
> As a quick workaround, I fixed the problem by altering line 462 of
> data/c.m4 to read
> 
> if (! (
>           $2)) YYERROR;

FTR, option —no-lines is another possible workaround.

I’ll apply the following changes to maint in a couple of days,
to leave some time for reviews.

Thanks for the report!

commit d0447d949b38e653029b1ffb484b361e8ee705f2
Author: Akim Demaille <address@hidden>
Date:   Tue May 29 09:00:59 2018 +0200

    bison: be git grep friendly
    
    * src/output.c (user_actions_output): Make calls to b4_case and
    b4_predicate_case explicit.

diff --git a/src/output.c b/src/output.c
index 7c98bb97..d1b90377 100644
--- a/src/output.c
+++ b/src/output.c
@@ -357,8 +357,8 @@ user_actions_output (FILE *out)
   for (r = 0; r < nrules; ++r)
     if (rules[r].action)
       {
-        fprintf (out, "b4_%scase(%d, [b4_syncline(%d, ",
-                 rules[r].is_predicate ? "predicate_" : "",
+        fprintf (out, "%s(%d, [b4_syncline(%d, ",
+                 rules[r].is_predicate ? "b4_predicate_case" : "b4_case",
                  r + 1, rules[r].action_location.start.line);
         string_output (out, rules[r].action_location.start.file);
         fprintf (out, ")\n[    %s]])\n\n", rules[r].action);


commit 5952fe5abfd2dfa69862791b67086cbd41f185d1
Author: Akim Demaille <address@hidden>
Date:   Tue May 29 09:02:21 2018 +0200

    glr: fix improperly placed synclines
    
    Predicates with GLR are issued with synclines in the middle of C code:
    
              case 2:
          if (! (#line 6 "sempred.y" /* glr.c:816  */
          new_syntax)) YYERROR;
        #line 793 "sempred.tab.c" /* glr.c:816  */
          break;
    
    Reported by Rici Lake.
    http://lists.gnu.org/archive/html/bug-bison/2018-05/msg00033.html
    
    * data/c.m4 (b4_predicate_case): Be sure to start on column 0.
    It would be nicer if b4_syncline could ensure this by itself
    (that would avoid ugly code when synclines are disabled), but that's
    way more work.
    * tests/glr-regression.at (Predicates): Be a real end-to-end test.
    This would have caught this error years ago...

diff --git a/data/c.m4 b/data/c.m4
index f2006b34..8607f55f 100644
--- a/data/c.m4
+++ b/data/c.m4
@@ -459,7 +459,8 @@ b4_syncline(address@hidden@], address@hidden@])
 # ------------------------------------
 m4_define([b4_predicate_case],
 [  case $1:
-    if (! ($2)) YYERROR;
+    if (! (
+$2)) YYERROR;
 b4_syncline(address@hidden@], address@hidden@])
     break;])
 
diff --git a/tests/glr-regression.at b/tests/glr-regression.at
index 2758b8f6..6ca6813d 100644
--- a/tests/glr-regression.at
+++ b/tests/glr-regression.at
@@ -1755,27 +1755,60 @@ AT_CLEANUP
 ## Predicates.                                                       ##
 ##                                                                   ##
 ## http://lists.gnu.org/archive/html/bug-bison/2013-10/msg00004.html ##
+## http://lists.gnu.org/archive/html/bug-bison/2018-05/msg00033.html ##
 ## ----------------------------------------------------------------- ##
 
 AT_SETUP([Predicates])
 
-# FIXME: We need genuine test cases with uses of %?.
-
 AT_DATA_GRAMMAR([input.y],
 [[%glr-parser
+%error-verbose
 %expect-rr 1
+%code requires
+{
+  #include <assert.h>
+  #include <stdbool.h>
+  bool new_syntax = false;
+  const char *input = YY_NULLPTR;
+  ]AT_YYERROR_DECLARE[
+  ]AT_YYLEX_DECLARE[
+}
 %%
-// Exercise "%?{...}" and "%? {...}".
 widget:
-  %? {new_syntax} "widget" id new_args  { $$ = f($3, $4); }
-| %?{!new_syntax} "widget" id old_args  { $$ = f($3, $4); }
+  %? {new_syntax} 'w' id new_args  { printf("new"); }
+| %?{!new_syntax} 'w' id old_args  { printf("old"); }
 ;
-id:;
-new_args:;
-old_args:;
+id: 'i';
+new_args: 'n';
+old_args: 'o';
 %%
+]AT_YYERROR_DEFINE[
+
+int
+yylex (void)
+{
+  return *input++;
+}
+
+int
+main (int argc, const char* argv[])
+{
+  assert (argc == 2); (void) argc;
+  // First char decides whether new, or old syntax.
+  // Then the input.
+  new_syntax = argv[1][0] == 'N';
+  input = argv[1] + 1;
+  return yyparse ();
+}
 ]])
 
-AT_BISON_CHECK([[input.y]])
+AT_BISON_CHECK([[-o input.c input.y]])
+AT_COMPILE([input])
+AT_PARSER_CHECK([[./input Nwin]], [0], [new])
+AT_PARSER_CHECK([[./input Owin]], [1], [], [[syntax error, unexpected 'n', 
expecting 'o'
+]])
+AT_PARSER_CHECK([[./input Owio]], [0], [old])
+AT_PARSER_CHECK([[./input Nwio]], [1], [], [[syntax error, unexpected 'o', 
expecting 'n'
+]])
 
 AT_CLEANUP