no-lines: avoid leaving an empty line instead of the syncline

Currently, with --no-lines, instead of "#line file line\n", we emit
"\n".  Let's emit nothing.

* data/skeletons/bison.m4 (b4_syncline): Emit at end-of-line when enabled.
* data/skeletons/bison.m4, data/skeletons/c.m4, data/skeletons/glr.cc,
* data/skeletons/lalr1.cc, src/output.c: Use dnl after b4_syncline to
avoid spurious empty lines.

* tests/synclines.at (Sync Lines): Make sure that --no-lines is like
grep -v #line.
* tests/calc.at: Make sure that a rich grammar file behaves properly
with %no-lines.

data/skeletons/bison.m4

@@ -448,9 +448,9 @@ m4_define([b4_symbol_action],
                    [],
                    [(*yylocationp)])dnl
     _b4_symbol_case([$1])[]dnl
-b4_syncline([b4_symbol([$1], [$2_line])], [b4_symbol([$1], [$2_file])])
+b4_syncline([b4_symbol([$1], [$2_line])], [b4_symbol([$1], [$2_file])])dnl
       b4_symbol([$1], [$2])
-b4_syncline([@oline@], [@ofile@])
+b4_syncline([@oline@], [@ofile@])dnl
         break;
 
 b4_dollar_popdef[]dnl
@@ -579,13 +579,15 @@ m4_define([b4_basename],
 [m4_bpatsubst([$1], [^.*/\([^/]+\)/*$], [\1])])
 
 
-# b4_syncline(LINE, FILE)
-# -----------------------
+# b4_syncline(LINE, FILE)dnl
+# --------------------------
+# Should always be following by a dnl.
+#
 # Emit "#line LINE FILE /* __LINE__ __FILE__ */".
 m4_define([b4_syncline],
 [b4_flag_if([synclines],
 [b4_sync_start([$1], [$2])[]dnl
-b4_sync_end([__line__], [b4_basename(m4_quote(__file__))])[]dnl
+b4_sync_end([__line__], [b4_basename(m4_quote(__file__))])
 ])])
 
 # b4_sync_start(LINE, FILE)
@@ -757,8 +759,10 @@ m4_define([b4_percent_define_get_kind],
           [m4_indir([b4_percent_define_kind(]$1[)])],
           [b4_fatal([[$0: undefined %%define variable '%s']], [$1])])])
 
-# b4_percent_define_get_syncline(VARIABLE)
-# ----------------------------------------
+# b4_percent_define_get_syncline(VARIABLE)dnl
+# -------------------------------------------
+# Should always be following by a dnl.
+#
 # Mimic muscle_percent_define_get_syncline in ../src/muscle-tab.h exactly.
 # That is, if the %define variable VARIABLE is undefined, complain fatally
 # since that's a Bison or skeleton error.  Otherwise, return its definition
@@ -974,8 +978,7 @@ m4_ifval([$1], [m4_define([b4_percent_code_bison_qualifiers(]$1[)])])dnl
 m4_ifdef(b4_macro_name,
 [b4_comment([m4_if([$#], [0], [[Unqualified %code]],
                    [["%code ]$1["]])[ blocks.]])
-b4_user_code([m4_indir(b4_macro_name)])
-])dnl
+b4_user_code([m4_indir(b4_macro_name)])])dnl
 m4_popdef([b4_macro_name])])
 
 # b4_percent_code_ifdef(QUALIFIER, IF-TRUE, [IF-FALSE])

data/skeletons/c++.m4

@@ -147,13 +147,13 @@ m4_if(m4_bregexp(b4_namespace_ref, [::[	 ]*$]), [-1], [],
                 [[namespace reference has a trailing "::"]])])
 
 m4_define([b4_namespace_open],
-[b4_user_code([b4_percent_define_get_syncline([[api.namespace]])
+[b4_user_code([b4_percent_define_get_syncline([[api.namespace]])dnl
 [namespace ]m4_bpatsubst(m4_dquote(m4_bpatsubst(m4_dquote(b4_namespace_ref),
                                                 [^\(.\)[	 ]*::], [\1])),
                          [::], [ { namespace ])[ {]])])
 
 m4_define([b4_namespace_close],
-[b4_user_code([b4_percent_define_get_syncline([[api.namespace]])
+[b4_user_code([b4_percent_define_get_syncline([[api.namespace]])dnl
 m4_bpatsubst(m4_dquote(m4_bpatsubst(m4_dquote(b4_namespace_ref[ ]),
                                     [^\(.\)[	 ]*\(::\)?\([^][:]\|:[^:]\)*],
                                     [\1])),
@@ -194,7 +194,7 @@ m4_define([b4_value_type_declare],
 [union\|union-directive],
 [[    union semantic_type
     {
-    ]b4_user_union_members[
+]b4_user_union_members[
     };]])])dnl
 ])
 

data/skeletons/c.m4

@@ -474,7 +474,7 @@ m4_define([b4_sync_start], [[#]line $1 $2])
 m4_define([b4_case],
 [  case $1:
 $2
-b4_syncline([@oline@], [@ofile@])
+b4_syncline([@oline@], [@ofile@])dnl
     break;])
 
 
@@ -484,7 +484,7 @@ m4_define([b4_predicate_case],
 [  case $1:
     if (! (
 $2)) YYERROR;
-b4_syncline([@oline@], [@ofile@])
+b4_syncline([@oline@], [@ofile@])dnl
     break;])
 
 
@@ -713,13 +713,13 @@ typedef ]b4_percent_define_get([[api.value.type]])[ ]b4_api_PREFIX[STYPE;
 [m4_bmatch(b4_percent_define_get([[api.value.type]]),
 [union\|union-directive],
 [[#if ! defined ]b4_api_PREFIX[STYPE && ! defined ]b4_api_PREFIX[STYPE_IS_DECLARED
-]b4_percent_define_get_syncline([[api.value.union.name]])[
-union ]b4_percent_define_get([[api.value.union.name]])[
+]b4_percent_define_get_syncline([[api.value.union.name]])dnl
+[union ]b4_percent_define_get([[api.value.union.name]])[
 {
 ]b4_user_union_members[
 };
-]b4_percent_define_get_syncline([[api.value.union.name]])[
-typedef union ]b4_percent_define_get([[api.value.union.name]])[ ]b4_api_PREFIX[STYPE;
+]b4_percent_define_get_syncline([[api.value.union.name]])dnl
+[typedef union ]b4_percent_define_get([[api.value.union.name]])[ ]b4_api_PREFIX[STYPE;
 # define ]b4_api_PREFIX[STYPE_IS_TRIVIAL 1
 # define ]b4_api_PREFIX[STYPE_IS_DECLARED 1
 #endif

data/skeletons/glr.c

@@ -202,8 +202,8 @@ b4_copyright([Skeleton interface for Bison GLR parsers in C],
 ]b4_cpp_guard_open([b4_spec_header_file])[
 ]b4_shared_declarations[
 ]b4_cpp_guard_close([b4_spec_header_file])[
-]b4_output_end
-])])
+]b4_output_end[
+]])])
 
 
 # ------------------------- #

data/skeletons/glr.cc

@@ -100,8 +100,8 @@ m4_defn([b4_initial_action])]))])[
 
 # Hijack the post prologue to declare yyerror.
 ]m4_append([b4_post_prologue],
-[b4_syncline([@oline@], [@ofile@])[
-]b4_function_declare([yyerror],
+[b4_syncline([@oline@], [@ofile@])dnl
+b4_function_declare([yyerror],
     [static void],b4_locations_if([
     [[const ]b4_namespace_ref::b4_parser_class[::location_type *yylocationp],
                         [yylocationp]],])
@@ -128,8 +128,8 @@ m4_if(b4_prefix, [yy], [],
 # Hijack the epilogue to define implementations (yyerror, parser member
 # functions etc.).
 m4_append([b4_epilogue],
-[b4_syncline([@oline@], [@ofile@])[
-
+[b4_syncline([@oline@], [@ofile@])dnl
+[
 /*------------------.
 | Report an error.  |
 `------------------*/
@@ -234,7 +234,7 @@ m4_pushdef([b4_parse_param], m4_defn([b4_parse_param_orig]))dnl
 
 #endif
 ]m4_popdef([b4_parse_param])dnl
-b4_namespace_close
+b4_namespace_close[]dnl
 ])
 
 

data/skeletons/lalr1.cc

@@ -111,9 +111,9 @@ b4_dollar_pushdef([yysym.value],
                   [],
                   [yysym.location])dnl
       _b4_symbol_case([$1])[]dnl
-b4_syncline([b4_symbol([$1], [$2_line])], [b4_symbol([$1], [$2_file])])
+b4_syncline([b4_symbol([$1], [$2_line])], [b4_symbol([$1], [$2_file])])dnl
         b4_symbol([$1], [$2])
-b4_syncline([@oline@], [@ofile@])
+b4_syncline([@oline@], [@ofile@])dnl
         break;
 
 m4_popdef([b4_symbol_value])[]dnl
@@ -412,9 +412,9 @@ b4_copyright([Skeleton interface for Bison LALR(1) parsers in C++])
 ]b4_disclaimer[
 ]b4_cpp_guard_open([b4_spec_header_file])[
 ]b4_shared_declarations(hh)[
-]b4_cpp_guard_close([b4_spec_header_file])
-b4_output_end
-])
+]b4_cpp_guard_close([b4_spec_header_file])[
+]b4_output_end[
+]])
 
 
 b4_output_begin([b4_parser_file_name])[

data/skeletons/yacc.c

@@ -1699,7 +1699,7 @@ yyreduce:
   }]], [[
   switch (yyn)
     {
-      ]b4_user_actions[
+]b4_user_actions[
       default: break;
     }]])[
   /* User semantic actions sometimes alter yychar, and that requires