Avoid "gcc -Wunused-parameter" warnings on the generated hash function.

Reported by Vinícius dos Santos Oliveira <vini.ipsmaker@gmail.com> in
<https://savannah.gnu.org/bugs/index.php?64393>.

* src/output.cc (Output::output_hash_function): If str is not used, emit
a cast from str to void. If len is not used, emit a cast from len to
void.
* tests/permut2.exp: Update.
* tests/permut3.exp: Likewise.
* tests/permutc2.exp: Likewise.

ChangeLog

@@ -1,3 +1,15 @@
+2023-07-08  Bruno Haible  <bruno@clisp.org>
+
+	Avoid "gcc -Wunused-parameter" warnings on the generated hash function.
+	Reported by Vinícius dos Santos Oliveira <vini.ipsmaker@gmail.com> in
+	<https://savannah.gnu.org/bugs/index.php?64393>.
+	* src/output.cc (Output::output_hash_function): If str is not used, emit
+	a cast from str to void. If len is not used, emit a cast from len to
+	void.
+	* tests/permut2.exp: Update.
+	* tests/permut3.exp: Likewise.
+	* tests/permutc2.exp: Likewise.
+
 2023-07-01  Bruno Haible  <bruno@clisp.org>
 
 	doc: Tweaks.

src/output.cc

@@ -1,5 +1,5 @@
 /* Output routines.
-   Copyright (C) 1989-1998, 2000, 2002-2004, 2006-2007, 2009, 2011-2012, 2016, 2018, 2021 Free Software Foundation, Inc.
+   Copyright (C) 1989-1998, 2000, 2002-2004, 2006-2007, 2009, 2011-2012, 2016, 2018, 2021, 2023 Free Software Foundation, Inc.
    Written by Douglas C. Schmidt <schmidt@ics.uci.edu>
    and Bruno Haible <bruno@clisp.org>.
 
@@ -815,12 +815,15 @@ Output::output_hash_function () const
             "#endif\n"
             "#endif\n");
 
-  if (/* The function does not use the 'str' argument?  */
+  /* Does the function use the 'str' argument?  */
-      _key_positions.get_size() == 0
+  bool uses_str = (_key_positions.get_size() > 0);
-      || /* The function uses 'str', but not the 'len' argument?  */
+  /* Does the function use the 'len' argument?  */
-         (!_hash_includes_len
+  bool uses_len =
-          && _key_positions[0] < _min_key_len
+     (_hash_includes_len
-          && _key_positions[_key_positions.get_size() - 1] != Positions::LASTCHAR))
+      || (_key_positions.get_size() > 0
+          && (_key_positions[0] >= _min_key_len
+              || _key_positions[_key_positions.get_size() - 1] == Positions::LASTCHAR)));
+  if (!uses_str || !uses_len)
     /* Pacify lint.  */
     printf ("/*ARGSUSED*/\n");
 
@@ -830,6 +833,9 @@ Output::output_hash_function () const
   if (option[CPLUSPLUS])
     printf ("%s::", option.get_class_name ());
   printf ("%s ", option.get_hash_name ());
+  /* We better not use [[__maybe_unused__]] or __attribute__ ((__unused__))
+     because support for these syntaxes in the compilers is constantly
+     changing.  */
   printf (option[KRC] ?
                  "(str, len)\n"
             "     %schar *str;\n"
@@ -879,6 +885,15 @@ Output::output_hash_function () const
               "    };\n");
     }
 
+  if (!uses_str)
+    /* The function does not use the 'str' argument.
+       Silence "gcc -Wunused-parameter".  */
+    printf ("  (void) str;\n");
+  if (!uses_len)
+    /* The function does not use the 'len' argument.
+       Silence "gcc -Wunused-parameter".  */
+    printf ("  (void) len;\n");
+
   if (_key_positions.get_size() == 0)
     {
       /* Trivial case: No key positions at all.  */

tests/permut2.exp

@@ -77,6 +77,7 @@ hash (register const char *str, register size_t len)
       4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
       4, 4, 4, 4, 4, 4, 4
     };
+  (void) len;
   return asso_values[(unsigned char)str[1]+1] + asso_values[(unsigned char)str[0]];
 }
 

tests/permut3.exp

@@ -77,6 +77,7 @@ hash (register const char *str, register size_t len)
       4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
       4, 4, 4, 4, 4, 4, 4
     };
+  (void) len;
   return asso_values[(unsigned char)str[1]+1] + asso_values[(unsigned char)str[0]];
 }
 

tests/permutc2.exp

@@ -122,6 +122,7 @@ hash (register const char *str, register size_t len)
       8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
       8, 8, 8, 8, 8, 8, 8, 8, 8
     };
+  (void) len;
   return asso_values[(unsigned char)str[1]+3] + asso_values[(unsigned char)str[0]];
 }