>From 8d5324941f8f88f2559f93dfbfc169383c167d0a Mon Sep 17 00:00:00 2001
From: Paul Eggert <address@hidden>
Date: Tue, 19 Sep 2017 10:00:35 -0700
Subject: [PATCH 3/7] maint: port to GCC 7.2

* configure.ac (WERROR_CFLAGS): Avoid -Wduplicated-branches.
* tailor.h (FALLTHROUGH): New macro, taken from Emacs.
* gzip.c (main): Use it.
---
 configure.ac | 1 +
 gzip.c       | 2 +-
 tailor.h     | 8 ++++++++
 3 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/configure.ac b/configure.ac
index 05aa681..ca4066c 100644
--- a/configure.ac
+++ b/configure.ac
@@ -106,6 +106,7 @@ if test "$gl_gcc_warnings" = yes; then
   nw="$nw -Wtraditional"            # Warns on #elif which we use often
   nw="$nw -Wcast-qual"              # Too many warnings for now
   nw="$nw -Wconversion"             # Too many warnings for now
+  nw="$nw -Wduplicated-branches"    # Too many false alarms
   nw="$nw -Wsystem-headers"         # Don't let system headers trigger warnings
   nw="$nw -Wsign-conversion"        # Too many warnings for now
   nw="$nw -Wtraditional-conversion" # Too many warnings for now
diff --git a/gzip.c b/gzip.c
index 3d2aeaf..32a229c 100644
--- a/gzip.c
+++ b/gzip.c
@@ -599,7 +599,7 @@ int main (int argc, char **argv)
         case '4' + ENV_OPTION:  case '5' + ENV_OPTION:  case '6' + ENV_OPTION:
         case '7' + ENV_OPTION:  case '8' + ENV_OPTION:  case '9' + ENV_OPTION:
             optc -= ENV_OPTION;
-            /* Fall through.  */
+            FALLTHROUGH;
         case '1':  case '2':  case '3':  case '4':
         case '5':  case '6':  case '7':  case '8':  case '9':
             level = optc - '0';
diff --git a/tailor.h b/tailor.h
index 8510599..aec3029 100644
--- a/tailor.h
+++ b/tailor.h
@@ -202,3 +202,11 @@
 #ifndef SET_BINARY_MODE
 #  define SET_BINARY_MODE(fd)
 #endif
+
+#ifndef FALLTHROUGH
+# if __GNUC__ < 7
+#  define FALLTHROUGH ((void) 0)
+# else
+#  define FALLTHROUGH __attribute__ ((__fallthrough__))
+# endif
+#endif
-- 
2.13.5