Re: Bison 3.7.90 (beta): example/c/lexcalc

[Akim Demaille]

> Le 18 août 2021 à 16:28, Dagobert Michelsen <dam@opencsw.org> a écrit :
> 
> Hi Akim,
> 
> Am 17.08.2021 um 08:59 schrieb Akim Demaille <akim@lrde.epita.fr>:
>>> Le 13 août 2021 à 09:50, Dagobert Michelsen <dam@opencsw.org> a écrit :
>>> and there are also errors on Solaris 10 Sparc:
>>> YACC     examples/c/lexcalc/parse.c
>>> /home/dam/mgar/pkg/bison/trunk/work/solaris10-sparc/build-isa-sparcv8plus/bison-3.7.90/examples/c/lexcalc/parse.y:
>>>  error: 1 nonterminal useless in grammar [-Werror=other]
>>> /home/dam/mgar/pkg/bison/trunk/work/solaris10-sparc/build-isa-sparcv8plus/bison-3.7.90/examples/c/lexcalc/parse.y:
>>>  error: 1 rule useless in grammar [-Werror=other]
>>> /home/dam/mgar/pkg/bison/trunk/work/solaris10-sparc/build-isa-sparcv8plus/bison-3.7.90/examples/c/lexcalc/parse.y:79.25-27:
>>>  error: start symbol NUM does not derive any sentence  
>>> 79 | %start input expression NUM
>>>    |                         ^~~  
>>> gmake[3]: *** [Makefile:9538: examples/c/lexcalc/parse.c] Error 1
>> 
>> That makes no sense to me: bison is emitting an incorrect
>> diagnostic.  I absolutely do not understand how this is possible.
>> Except if we actually are not running the shipped bison, but another
>> one.
>> 
>> Could you please run `make check-examples V=1`?
> 
> Sure:
> 
> dam@unstable10s 
> [unstable10s]:/home/dam/mgar/pkg/bison/trunk/work/solaris10-sparc/build-isa-sparcv8plus/bison-3.7.90
>  > gmake check-examples V=1 
> /bin/bash ./build-aux/ylwrap examples/c/lexcalc/parse.y y.tab.c 
> examples/c/lexcalc/parse.c y.tab.h `echo examples/c/lexcalc/parse.c | sed -e 
> s/cc$/hh/ -e s/cpp$/hpp/ -e s/cxx$/hxx/ -e s/c++$/h++/ -e s/c$/h/` y.output 
> examples/c/lexcalc/parse.output -- ./tests/bison -o y.tab.c --defines -Werror 
> -Wall,dangling-alias --report=all --no-lines 
> /home/dam/mgar/pkg/bison/trunk/work/solaris10-sparc/build-isa-sparcv8plus/bison-3.7.90/examples/c/lexcalc/parse.y:
>  error: 1 nonterminal useless in grammar [-Werror=other]
> /home/dam/mgar/pkg/bison/trunk/work/solaris10-sparc/build-isa-sparcv8plus/bison-3.7.90/examples/c/lexcalc/parse.y:
>  error: 1 rule useless in grammar [-Werror=other]
> /home/dam/mgar/pkg/bison/trunk/work/solaris10-sparc/build-isa-sparcv8plus/bison-3.7.90/examples/c/lexcalc/parse.y:79.25-27:
>  error: start symbol NUM does not derive any sentence
>   79 | %start input expression NUM
>      |                         ^~~
> gmake: *** [Makefile:9538: examples/c/lexcalc/parse.c] Error 1

This still does not make sense to me.  But let's postpone this issue, since 
it's about an unfinished feature that I don't want to demonstrate in 3.8.  So I 
have installed the following "fix".  But in the future we will have to dig 
deeper.

Thanks a lot for the feedback!

commit a70e75b8a41755ab96ab211a0ea111ac68a4aadd
Author: Akim Demaille <akim.demaille@gmail.com>
Date:   Thu Aug 19 09:16:00 2021 +0200

    examples: don't demonstrate multistart, which is not part of 3.8
    
    Besides, for mysterious reasons, this fails on some environment.
    Reported by Dagobert Michelsen.
    <https://lists.gnu.org/archive/html/bug-bison/2021-08/msg00008.html>
    
    * examples/c/lexcalc/lexcalc.test, examples/c/lexcalc/parse.y,
    * examples/c/lexcalc/scan.l: Revert to a single-start example.

diff --git a/TODO b/TODO
index 2e6e7d5a..4ef16d8d 100644
--- a/TODO
+++ b/TODO
@@ -1,6 +1,3 @@
-* 3.8
-Don't showcase multi start.
-
 * Soon
 ** scan-code
 The default case is scanning char-per-char.
diff --git a/examples/c/lexcalc/lexcalc.test b/examples/c/lexcalc/lexcalc.test
index df8da33b..7559a21e 100644
--- a/examples/c/lexcalc/lexcalc.test
+++ b/examples/c/lexcalc/lexcalc.test
@@ -38,26 +38,9 @@ run -noerr 0 9 -p
 cat >input <<EOF
 (1+2) *
 EOF
-run 1 'err: 1.8-2.0: syntax error, unexpected end of line, expecting ( or 
number
-err: errors: 1'
+run 1 'err: 1.8-2.0: syntax error, unexpected end of line, expecting ( or 
number'
 
 cat >input <<EOF
 1 / (2 - 2)
 EOF
-run 1 'err: 1.1-11: error: division by zero
-err: errors: 1'
-
-
-# Multistart: parse "expression" instead of "input".
-cat >input <<EOF
-1+2*3
-EOF
-run 0 'expression: 7' -e
-
-cat >input <<EOF
-1
-2
-EOF
-run 1 'expression: failure
-err: 2.1: syntax error, unexpected number, expecting end of file
-err: errors: 1' -e
+run 1 'err: 1.1-11: error: division by zero'
diff --git a/examples/c/lexcalc/parse.y b/examples/c/lexcalc/parse.y
index aa72a410..ee559887 100644
--- a/examples/c/lexcalc/parse.y
+++ b/examples/c/lexcalc/parse.y
@@ -25,10 +25,10 @@
 {
   // Tell Flex the expected prototype of yylex.
 #define YY_DECL                                 \
-  yytoken_kind_t yylex (YYSTYPE* yylval, YYLTYPE *yylloc)
+  yytoken_kind_t yylex (YYSTYPE* yylval, YYLTYPE *yylloc, int *nerrs)
   YY_DECL;
 
-  void yyerror (const YYLTYPE *loc, const char *msg);
+  void yyerror (const YYLTYPE *loc, int *nerrs, const char *msg);
 }
 
 // Emitted on top of the implementation file.
@@ -62,6 +62,9 @@
 // Enable debug traces (see yydebug in main).
 %define parse.trace
 
+// Error count, exchanged between main, yyparse and yylex.
+%param {int *nerrs}
+
 %token
   PLUS   "+"
   MINUS  "-"
@@ -73,11 +76,9 @@
 ;
 
 %token <int> NUM "number"
-%type <int> exp expression line
+%type <int> exp
 %printer { fprintf (yyo, "%d", $$); } <int>
 
-%start input expression NUM
-
 // Precedence (from lowest to highest) and associativity.
 %left "+" "-"
 %left "*" "/"
@@ -90,12 +91,8 @@ input:
 ;
 
 line:
-  exp EOL   { $$ = $exp; printf ("%d\n", $$); }
-| error EOL { $$ = 0; yyerrok; }
-;
-
-expression:
-  exp EOL  { $$ = $exp; }
+  exp EOL   { printf ("%d\n", $exp); }
+| error EOL { yyerrok; }
 ;
 
 exp:
@@ -106,7 +103,7 @@ exp:
   {
     if ($3 == 0)
       {
-        yyerror (&@$, "error: division by zero");
+        yyerror (&@$, nerrs, "error: division by zero");
         YYERROR;
       }
     else
@@ -118,41 +115,24 @@ exp:
 %%
 // Epilogue (C code).
 
-void yyerror (const YYLTYPE *loc, const char *msg)
+void yyerror (const YYLTYPE *loc, int *nerrs, const char *msg)
 {
   YYLOCATION_PRINT (stderr, loc);
   fprintf (stderr, ": %s\n", msg);
+  ++*nerrs;
 }
 
 int main (int argc, const char *argv[])
 {
   // Possibly enable parser runtime debugging.
   yydebug = !!getenv ("YYDEBUG");
-  int parse_expression_p = 0;
-  int nerrs = 0;
-
   // Enable parse traces on option -p.
   for (int i = 1; i < argc; ++i)
-    if (strcmp (argv[i], "-e") == 0)
-      parse_expression_p = 1;
-    else if (strcmp (argv[i], "-p") == 0)
+    if (strcmp (argv[i], "-p") == 0)
       yydebug = 1;
 
-  if (parse_expression_p)
-    {
-      yyparse_expression_t res = yyparse_expression ();
-      nerrs = res.yynerrs;
-      if (res.yystatus == 0)
-        printf ("expression: %d\n", res.yyvalue);
-      else
-        printf ("expression: failure\n");
-    }
-  else
-    nerrs = yyparse_input ().yynerrs;
-
-  if (nerrs)
-    fprintf (stderr, "errors: %d\n", nerrs);
-
+  int nerrs = 0;
+  yyparse (&nerrs);
   // Exit on failure if there were errors.
   return !!nerrs;
 }
diff --git a/examples/c/lexcalc/scan.l b/examples/c/lexcalc/scan.l
index 51129a56..983fbdaf 100644
--- a/examples/c/lexcalc/scan.l
+++ b/examples/c/lexcalc/scan.l
@@ -61,7 +61,7 @@
   errno = 0;
   long n = strtol (yytext, NULL, 10);
   if (! (INT_MIN <= n && n <= INT_MAX && errno != ERANGE))
-    yyerror (yylloc, "integer is out of range");
+    yyerror (yylloc, nerrs, "integer is out of range");
   yylval->TOK_NUM = (int) n;
   return TOK_NUM;
 }
@@ -71,7 +71,7 @@
  /* Ignore white spaces. */
 [ \t]+   LOCATION_STEP (); continue;
 
-.        yyerror (yylloc, "syntax error, invalid character"); continue;
+.        yyerror (yylloc, nerrs, "syntax error, invalid character"); continue;
 
 <<EOF>>  return TOK_YYEOF;
 %%