Avoid "implicit fallthrough" warnings in the generated code.

11 files changed, 298 insertions, 3 deletions

diff --git a/ChangeLog b/ChangeLog
index 21218d7..0f84fee 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+2018-07-25  Bruno Haible  <bruno@clisp.org>
+
+	Avoid "implicit fallthrough" warnings in the generated code.
+	Reported by Phil Willoughby at
+	<https://lists.gnu.org/archive/html/bug-gperf/2018-07/msg00002.html>.
+	* src/output.cc (Output::output_hash_function): Emit a more elaborate
+	fallthrough marker.
+	* tests/*.exp: Update.
+
 2018-04-24  Bruno Haible  <bruno@clisp.org>
 
 	Support input files with CR/LF line terminators.
diff --git a/NEWS b/NEWS
index 14deb90..8412142 100644
--- a/NEWS
+++ b/NEWS
@@ -3,6 +3,8 @@ New in 3.2:
   Unix line terminators (LF).
   Note: This is an incompatible change. If you want to use a keyword that
   ends in a CR byte, such as xyz<CR>, write it as "xyz\r".
+* The generated code avoids "implicit fallthrough" warnings in 'switch'
+  statements.
 
 New in 3.1:
 * The generated C code is now in ANSI-C by default. If you want to support
diff --git a/src/output.cc b/src/output.cc
index d8a8ba9..2e95a31 100644
--- a/src/output.cc
+++ b/src/output.cc
@@ -1,5 +1,5 @@
 /* Output routines.
-   Copyright (C) 1989-1998, 2000, 2002-2004, 2006-2007, 2009, 2011-2012, 2016 Free Software Foundation, Inc.
+   Copyright (C) 1989-1998, 2000, 2002-2004, 2006-2007, 2009, 2011-2012, 2016, 2018 Free Software Foundation, Inc.
    Written by Douglas C. Schmidt <schmidt@ics.uci.edu>
    and Bruno Haible <bruno@clisp.org>.
 
@@ -932,6 +932,15 @@ Output::output_hash_function () const
       else
         {
           /* We've got to use the correct, but brute force, technique.  */
+          /* Pseudo-statement or comment that avoids a compiler warning or
+             lint warning.  */
+          const char * const fallthrough_marker =
+            "#if defined __cplusplus && __cplusplus >= 201703L\n"
+            "      [[fallthrough]];\n"
+            "#elif defined __GNUC__ && __GNUC__ >= 7\n"
+            "      __attribute__ ((__fallthrough__));\n"
+            "#endif\n"
+            "      /*FALLTHROUGH*/\n";
           /* It doesn't really matter whether hval is an 'int' or
              'unsigned int', but 'unsigned int' gives fewer warnings.  */
           printf ("  %sunsigned int hval = %s;\n\n"
@@ -951,7 +960,7 @@ Output::output_hash_function () const
               do
                 {
                   if (i > key_pos)
-                    printf ("      /*FALLTHROUGH*/\n"); /* Pacify lint.  */
+                    printf ("%s", fallthrough_marker);
                   for ( ; i > key_pos; i--)
                     printf ("      case %d:\n", i);
 
@@ -964,7 +973,7 @@ Output::output_hash_function () const
               while (key_pos != PositionIterator::EOS && key_pos != Positions::LASTCHAR);
 
               if (i >= _min_key_len)
-                printf ("      /*FALLTHROUGH*/\n"); /* Pacify lint.  */
+                printf ("%s", fallthrough_marker);
               for ( ; i >= _min_key_len; i--)
                 printf ("      case %d:\n", i);
             }
diff --git a/tests/c-parse.exp b/tests/c-parse.exp
index 3b46a35..d88878c 100644
--- a/tests/c-parse.exp
+++ b/tests/c-parse.exp
@@ -86,6 +86,11 @@ hash (str, len)
     {
       default:
         hval += asso_values[(unsigned char)str[2]];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 2:
       case 1:
diff --git a/tests/charsets.exp b/tests/charsets.exp
index 2be2ddf..4af888f 100644
--- a/tests/charsets.exp
+++ b/tests/charsets.exp
@@ -93,6 +93,11 @@ hash (register const char *str, register size_t len)
     {
       default:
         hval += asso_values[(unsigned char)str[21]];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 21:
       case 20:
@@ -106,33 +111,83 @@ hash (register const char *str, register size_t len)
       case 12:
       case 11:
         hval += asso_values[(unsigned char)str[10]+1];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 10:
         hval += asso_values[(unsigned char)str[9]];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 9:
         hval += asso_values[(unsigned char)str[8]+1];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 8:
         hval += asso_values[(unsigned char)str[7]+3];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 7:
         hval += asso_values[(unsigned char)str[6]];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 6:
         hval += asso_values[(unsigned char)str[5]];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 5:
         hval += asso_values[(unsigned char)str[4]];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 4:
         hval += asso_values[(unsigned char)str[3]];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 3:
         hval += asso_values[(unsigned char)str[2]];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 2:
         hval += asso_values[(unsigned char)str[1]+1];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 1:
         hval += asso_values[(unsigned char)str[0]];
diff --git a/tests/chill.exp b/tests/chill.exp
index faf4bd7..3fc858a 100644
--- a/tests/chill.exp
+++ b/tests/chill.exp
@@ -84,90 +84,235 @@ hash (str, len)
     {
       default:
         hval += asso_values[(unsigned char)str[29]];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 29:
         hval += asso_values[(unsigned char)str[28]];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 28:
         hval += asso_values[(unsigned char)str[27]];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 27:
         hval += asso_values[(unsigned char)str[26]];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 26:
         hval += asso_values[(unsigned char)str[25]];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 25:
         hval += asso_values[(unsigned char)str[24]];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 24:
         hval += asso_values[(unsigned char)str[23]];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 23:
         hval += asso_values[(unsigned char)str[22]];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 22:
         hval += asso_values[(unsigned char)str[21]];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 21:
         hval += asso_values[(unsigned char)str[20]];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 20:
         hval += asso_values[(unsigned char)str[19]];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 19:
         hval += asso_values[(unsigned char)str[18]];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 18:
         hval += asso_values[(unsigned char)str[17]];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 17:
         hval += asso_values[(unsigned char)str[16]];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 16:
         hval += asso_values[(unsigned char)str[15]];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 15:
         hval += asso_values[(unsigned char)str[14]];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 14:
         hval += asso_values[(unsigned char)str[13]];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 13:
         hval += asso_values[(unsigned char)str[12]];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 12:
         hval += asso_values[(unsigned char)str[11]];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 11:
         hval += asso_values[(unsigned char)str[10]];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 10:
         hval += asso_values[(unsigned char)str[9]];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 9:
         hval += asso_values[(unsigned char)str[8]];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 8:
         hval += asso_values[(unsigned char)str[7]];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 7:
         hval += asso_values[(unsigned char)str[6]];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 6:
         hval += asso_values[(unsigned char)str[5]];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 5:
         hval += asso_values[(unsigned char)str[4]];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 4:
         hval += asso_values[(unsigned char)str[3]];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 3:
         hval += asso_values[(unsigned char)str[2]];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 2:
         hval += asso_values[(unsigned char)str[1]+1];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 1:
         hval += asso_values[(unsigned char)str[0]];
diff --git a/tests/cplusplus.exp b/tests/cplusplus.exp
index 148ad96..20c4471 100644
--- a/tests/cplusplus.exp
+++ b/tests/cplusplus.exp
@@ -86,11 +86,21 @@ hash (str, len)
     {
       default:
         hval += asso_values[(unsigned char)str[6]];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 6:
       case 5:
       case 4:
         hval += asso_values[(unsigned char)str[3]];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 3:
       case 2:
diff --git a/tests/java.exp b/tests/java.exp
index 44fa7ff..7176106 100644
--- a/tests/java.exp
+++ b/tests/java.exp
@@ -110,6 +110,11 @@ hash (str, len)
     {
       default:
         hval += asso_values[(unsigned char)str[2]];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 2:
       case 1:
diff --git a/tests/languages.exp b/tests/languages.exp
index 2de2500..36d36d7 100644
--- a/tests/languages.exp
+++ b/tests/languages.exp
@@ -97,13 +97,28 @@ hash (register const char *str, register size_t len)
     {
       default:
         hval += asso_values[(unsigned char)str[4]+1];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 4:
       case 3:
         hval += asso_values[(unsigned char)str[2]];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 2:
         hval += asso_values[(unsigned char)str[1]+9];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 1:
         hval += asso_values[(unsigned char)str[0]];
diff --git a/tests/modula2.exp b/tests/modula2.exp
index 02001b7..658223b 100644
--- a/tests/modula2.exp
+++ b/tests/modula2.exp
@@ -81,24 +81,59 @@ hash (register const char *str, register size_t len)
     {
       default:
         hval += asso_values[(unsigned char)str[7]];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 7:
         hval += asso_values[(unsigned char)str[6]];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 6:
         hval += asso_values[(unsigned char)str[5]];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 5:
         hval += asso_values[(unsigned char)str[4]];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 4:
         hval += asso_values[(unsigned char)str[3]];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 3:
         hval += asso_values[(unsigned char)str[2]];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 2:
         hval += asso_values[(unsigned char)str[1]];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 1:
         hval += asso_values[(unsigned char)str[0]];
diff --git a/tests/objc.exp b/tests/objc.exp
index 2c3374b..379e668 100644
--- a/tests/objc.exp
+++ b/tests/objc.exp
@@ -84,6 +84,11 @@ hash (register const char *str, register size_t len)
     {
       default:
         hval += asso_values[(unsigned char)str[2]];
+#if defined __cplusplus && __cplusplus >= 201703L
+      [[fallthrough]];
+#elif defined __GNUC__ && __GNUC__ >= 7
+      __attribute__ ((__fallthrough__));
+#endif
       /*FALLTHROUGH*/
       case 2:
       case 1: