From: Ben Hutchings <ben@decadent.org.uk>
Date: Fri, 18 Sep 2015 21:59:17 +0200
Subject: gzip: Fix silent fallback to decompression
Bug-Debian: https://bugs.debian.org/355809
Forwarded: http://www.zytor.com/pipermail/klibc/2016-January/003892.html

If the gzip utilities are built without support for compression,
they will always attempt to carry out decompression even if the
command name and options don't imply that.  Instead they should
fail with an explicit error in this case.

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
--- a/usr/gzip/gzip.c
+++ b/usr/gzip/gzip.c
@@ -90,8 +90,11 @@ int level = 6;        /* compression lev
 #endif
 
 int to_stdout;        /* output to stdout (-c) */
-#ifndef decompress
+#ifdef decompress
+int decompress_wanted;
+#else
 int decompress;       /* decompress (-d) */
+#define decompress_wanted decompress
 #endif
 int force;            /* don't ask questions, compress links (-f) */
 int no_name = -1;     /* don't save or restore the original file name */
@@ -259,17 +262,13 @@ int main (argc, argv)
      * Systems which do not support links can still use -d or -dc.
      * Ignore an .exe extension for MSDOS, OS/2 and VMS.
      */
-#ifndef decompress
     if (  strncmp(progname, "un",  2) == 0     /* ungzip, uncompress */
        || strncmp(progname, "gun", 3) == 0) {  /* gunzip */
-	decompress = 1;
+	decompress_wanted = 1;
     }
-#endif
     if (strequ(progname+1, "cat")       /* zcat, pcat, gcat */
 	|| strequ(progname, "gzcat")) {    /* gzcat */
-#ifndef decompress
-	decompress = 1;
-#endif
+	decompress_wanted = 1;
 	to_stdout = 1;
     }
 #endif
@@ -282,9 +281,7 @@ int main (argc, argv)
 	case 'c':
 	    to_stdout = 1; break;
 	case 'd':
-#ifndef decompress
-	    decompress = 1;
-#endif
+	    decompress_wanted = 1;
 	    break;
 	case 'f':
 	    force++; break;
@@ -308,9 +305,7 @@ int main (argc, argv)
             break;
 	case 't':
 	    test = to_stdout = 1;
-#ifndef decompress
-	    decompress = 1;
-#endif
+	    decompress_wanted = 1;
 	    break;
 	case 'v':
 	    verbose++; quiet = 0; break;
@@ -329,6 +324,14 @@ int main (argc, argv)
 	}
     } /* loop on all arguments */
 
+#ifndef SUPPORT_ZIP
+    if (!decompress_wanted) {
+	fprintf(stderr, "%s: this version does not support compression\n",
+		progname);
+	do_exit(ERROR);
+    }
+#endif
+
     /* By default, save name and timestamp on compression but do not
      * restore them on decompression.
      */