maint.mk: new syntax-check rule: prohibit empty lines at end of file

* top/maint.mk (sc_prohibit_empty_lines_at_EOF): New rule.

diff --git a/ChangeLog b/ChangeLog
index e66d23e..c128892 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,8 @@
 2010-04-10  Jim Meyering  <meyering@redhat.com>
 
+       maint.mk: new syntax-check rule: prohibit empty lines at end of file
+       * top/maint.mk (sc_prohibit_empty_lines_at_EOF): New rule.
+
        maint.mk: correct a diagnostic
        * top/maint.mk (sc_prohibit_HAVE_MBRTOWC): Fix obsolete use of $re
        in diagnostic; now use $prohibit.

diff --git a/top/maint.mk b/top/maint.mk
index df8e150..6bfb4c1 100644 (file)
--- a/top/maint.mk
+++ b/top/maint.mk
@@ -659,6 +659,29 @@ sc_prohibit_cvs_keyword:
        halt='do not use CVS keyword expansion'                         \
          $(_sc_search_regexp)
 
+# The following tail+perl pipeline would be more concise, and would
+# produce slightly better output (including counts) if written as
+#   perl -ln -0777 -e '/\n(\n+)$/ and print "$ARGV: ".length $1' ...
+# but that would be far less efficient, reading the entire contents
+# of each file, rather than just the last few bytes of each.
+#
+# This is a perl script that operates on the output of
+# tail -n1 TWO_OR_MORE_FILES
+# Print the name of each file that ends in two or more newline bytes.
+# Exit nonzero if at least one such file is found, otherwise, exit 0.
+#
+# Use this if you want to remove trailing empty lines from selected files:
+#   perl -pi -0777 -e 's/\n\n+$/\n/' files...
+#
+detect_empty_lines_at_EOF_ =                                           \
+  /^==> ([^\n]+) <==\n\n/m and (print "$$1\n"), $$fail = 1;            \
+  END { exit defined $$fail }
+sc_prohibit_empty_lines_at_EOF:
+       @tail -n1 $$($(VC_LIST_EXCEPT)) /dev/null                       \
+           | perl -00 -ne '$(detect_empty_lines_at_EOF_)'              \
+         || { echo '$(ME): the above files end with empty line(s)'     \
+               1>&2; exit 1; } || :;                                   \
+
 # Make sure we don't use st_blocks.  Use ST_NBLOCKS instead.
 # This is a bit of a kludge, since it prevents use of the string
 # even in comments, but for now it does the job with no false positives.