[PATCH v2] Avoid warnings from gcc -Wunused y.tab.c

[Jonathan Nieder]

Hi Joel,

Here is an updated patch incorporating all your suggestions except for
the last one.

Joel E. Denny wrote:

> How does the b4_locations_if part of this change help?  If it isn't really 
> necessary, then let's drop it.  As far as I can tell, the addition of 
> `defined YYLTYPE_IS_TRIVIAL &&' is sufficient.

I tried to make it a little clearer what the conditional is for in
this version.  If you still think the conditional should be dropped,
let me know and I’ll send a version without it.

Ciao,
-- %< --
>From 81895390b3b97540e4ade42031449700d10d62bd Mon Sep 17 00:00:00 2001
From: Jonathan Nieder <address@hidden>
Date: Sat, 12 Dec 2009 15:43:18 -0600
Subject: [PATCH] Avoid warnings from gcc -Wunused y.tab.c

Building bison-produced parsers can result in a few warnings:

        y.tab.c:383:6: warning: "YYENABLE_NLS" is not defined
        y.tab.c:1271:6: warning: "YYLTYPE_IS_TRIVIAL" is not defined

These warnings are not revealing any actual problem (it is
perfectly reasonable to use #if FOO even if FOO is not defined).
Suppress them by checking if preprocessor symbols are defined
before using their values.

While at it, do not use the YYLTYPE_IS_TRIVIAL symbol in the
generated parser source if location tracking is not enabled.
(Most uses were protected by b4_locations_if already.)
---
 ChangeLog     |   15 +++++++++++++++
 data/glr.c    |    4 ++--
 data/lalr1.cc |    2 +-
 data/yacc.c   |   14 ++++++++++----
 4 files changed, 28 insertions(+), 7 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 2c5d33e..1f7fd6b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,18 @@
+2009-12-15  Jonathan Nieder  <address@hidden>
+
+       Check defined FOO && FOO instead of FOO when testing
+       user-defined preprocessor symbols.
+       This avoids warnings from gcc -Wunused y.tab.c.
+       * data/glr.c: Test if YYENABLE_NLS is defined before using it.
+       * data/lalr1.cc: Likewise.
+       * data/yacc.c: Likewise.
+       * data/glr.c: Test if YYLTYPE_IS_TRIVIAL is defined before
+       using it.
+       * data/yacc.c: If location tracking is enabled, test if
+       YYLTYPE_IS_TRIVIAL is defined before using it.  Otherwise, do
+       not use it: define YY_LOCATION_PRINT as a no-op unconditionally
+       and add a comment explaining why.
+
 2009-12-15  Joel E. Denny  <address@hidden>
 
        autoconf: update to latest for fix of M4 detection.
diff --git a/data/glr.c b/data/glr.c
index 6f1f7ee..e73b251 100644
--- a/data/glr.c
+++ b/data/glr.c
@@ -256,7 +256,7 @@ b4_percent_code_get[]dnl
 #include <string.h>
 
 #ifndef YY_
-# if YYENABLE_NLS
+# if defined YYENABLE_NLS && YYENABLE_NLS
 #  if ENABLE_NLS
 #   include <libintl.h> /* INFRINGES ON USER NAME SPACE */
 #   define YY_(msgid) dgettext ("bison-runtime", msgid)
@@ -2264,7 +2264,7 @@ yyrecoverSyntaxError (yyGLRStack* 
yystackp]b4_user_formals[)
   yychar = YYEMPTY;
   yylval = yyval_default;
 ]b4_locations_if([
-#if YYLTYPE_IS_TRIVIAL
+#if defined YYLTYPE_IS_TRIVIAL && YYLTYPE_IS_TRIVIAL
   yylloc.first_line   = yylloc.last_line   = ]b4_location_initial_line[;
   yylloc.first_column = yylloc.last_column = ]b4_location_initial_column[;
 #endif
diff --git a/data/lalr1.cc b/data/lalr1.cc
index 1a2777e..9e0d522 100644
--- a/data/lalr1.cc
+++ b/data/lalr1.cc
@@ -398,7 +398,7 @@ m4_if(b4_prefix, [yy], [],
 b4_percent_code_get[]dnl
 
 [#ifndef YY_
-# if YYENABLE_NLS
+# if defined YYENABLE_NLS && YYENABLE_NLS
 #  if ENABLE_NLS
 #   include <libintl.h> /* FIXME: INFRINGES ON USER NAME SPACE */
 #   define YY_(msgid) dgettext ("bison-runtime", msgid)
diff --git a/data/yacc.c b/data/yacc.c
index ea2ae14..04c6a90 100644
--- a/data/yacc.c
+++ b/data/yacc.c
@@ -374,7 +374,7 @@ typedef short int yytype_int16;
 #define YYSIZE_MAXIMUM ((YYSIZE_T) -1)
 
 #ifndef YY_
-# if YYENABLE_NLS
+# if defined YYENABLE_NLS && YYENABLE_NLS
 #  if ENABLE_NLS
 #   include <libintl.h> /* INFRINGES ON USER NAME SPACE */
 #   define YY_(msgid) dgettext ("bison-runtime", msgid)
@@ -662,13 +662,13 @@ while (YYID (0))
     while (YYID (0))
 #endif
 
-
+]b4_locations_if([[
 /* YY_LOCATION_PRINT -- Print the location on the stream.
    This macro was not mandated originally: define only if we know
    we won't break user code: when these are the locations we know.  */
 
 #ifndef YY_LOCATION_PRINT
-# if YYLTYPE_IS_TRIVIAL
+# if defined YYLTYPE_IS_TRIVIAL && YYLTYPE_IS_TRIVIAL
 #  define YY_LOCATION_PRINT(File, Loc)                 \
      fprintf (File, "%d.%d-%d.%d",                     \
              (Loc).first_line, (Loc).first_column,     \
@@ -677,7 +677,13 @@ while (YYID (0))
 #  define YY_LOCATION_PRINT(File, Loc) ((void) 0)
 # endif
 #endif
+]], [[
+/* This macro is provided for backwards compatibility. */
 
+#ifndef YY_LOCATION_PRINT
+# define YY_LOCATION_PRINT(File, Loc) ((void) 0)
+#endif
+]])[
 
 /* YYLEX -- calling `yylex' with the right arguments.  */
 
@@ -1192,7 +1198,7 @@ b4_c_function_def([[yyparse]], [[int]], b4_parse_param)[
   yyvsp = yyvs;]b4_locations_if([[
   yylsp = yyls;
 
-#if YYLTYPE_IS_TRIVIAL
+#if defined YYLTYPE_IS_TRIVIAL && YYLTYPE_IS_TRIVIAL
   /* Initialize the default location before parsing starts.  */
   yylloc.first_line   = yylloc.last_line   = ]b4_location_initial_line[;
   yylloc.first_column = yylloc.last_column = ]b4_location_initial_column[;
-- 
1.6.5.4