syntax-check: mandate space after mid-line semicolon

Enforce the style cleanup in the previous patch.

* build-aux/bracket-spacing.pl: Enforce trailing spacing.
* cfg.mk (bracket-spacing-check): Tweak error wording.
* docs/hacking.html.in: Document the rule.
* HACKING: Regenerate.

Signed-off-by: Eric Blake <eblake@redhat.com>

HACKING

@@ -318,6 +318,29 @@ immediately prior to any closing bracket. E.g.
       int foo(int wizz);    // Good
 
 
+Semicolons
+==========
+Semicolons should never have a space beforehand. Inside the condition of a
+"for" loop, there should always be a space or line break after each semicolon,
+except for the special case of an infinite loop (although more infinite loops
+use "while"). While not enforced, loop counters generally use post-increment.
+
+      for (i = 0 ;i < limit ; ++i) { // Bad
+      for (i = 0; i < limit; i++) { // Good
+      for (;;) { // ok
+      while (1) { // Better
+
+Empty loop bodies are better represented with curly braces and a comment,
+although use of a semicolon is not currently rejected.
+
+      while ((rc = waitpid(pid, &st, 0) == -1) &&
+             errno == EINTR); // ok
+      while ((rc = waitpid(pid, &st, 0) == -1) &&
+             errno == EINTR) { // Better
+          /* nothing */
+      }
+
+
 Curly braces
 ============
 Omit the curly braces around an "if", "while", "for" etc. body only when that

build-aux/bracket-spacing.pl

@@ -1,6 +1,7 @@
 #!/usr/bin/perl
 #
 # bracket-spacing.pl: Report any usage of 'function (..args..)'
+# Also check for other syntax issues, such as correct use of ';'
 #
 # This library is free software; you can redistribute it and/or
 # modify it under the terms of the GNU Lesser General Public
@@ -31,6 +32,9 @@ foreach my $file (@ARGV) {
     while (defined (my $line = <FILE>)) {
         my $data = $line;
 
+        # Kill any quoted ; or "
+        $data =~ s,'[";]','X',g;
+
         # Kill any quoted strings
         $data =~ s,"([^\\\"]|\\.)*","XXX",g;
 
@@ -125,6 +129,14 @@ foreach my $file (@ARGV) {
             $ret = 1;
             last;
         }
+
+        # Require EOL, macro line continuation, or whitespace after ";".
+        # Allow "for (;;)" as an exception.
+        while ($data =~ /;[^	 \\\n;)]/) {
+            print "$file:$.: $line";
+            $ret = 1;
+            last;
+        }
     }
     close FILE;
 }

cfg.mk

@@ -845,7 +845,8 @@ syntax-check: $(top_srcdir)/HACKING bracket-spacing-check
 bracket-spacing-check:
 	$(AM_V_GEN)files=`$(VC_LIST) | grep '\.c$$'`; \
 	$(PERL) $(top_srcdir)/build-aux/bracket-spacing.pl $$files || \
-          (echo $(ME): incorrect whitespace around brackets, see HACKING for rules && exit 1)
+	  { echo "$(ME): incorrect whitespace, see HACKING for rules" 2>&; \
+	    exit 1; }
 
 # sc_po_check can fail if generated files are not built first
 sc_po_check: \

docs/hacking.html.in

@@ -377,6 +377,35 @@
       int foo(int wizz);    // Good
 </pre>
 
+    <h2><a name="semicolon">Semicolons</a></h2>
+
+    <p>
+      Semicolons should never have a space beforehand.  Inside the
+      condition of a <code>for</code> loop, there should always be a
+      space or line break after each semicolon, except for the special
+      case of an infinite loop (although more infinite loops
+      use <code>while</code>).  While not enforced, loop counters
+      generally use post-increment.
+    </p>
+    <pre>
+      for (i = 0 ;i &lt; limit ; ++i) { // Bad
+      for (i = 0; i &lt; limit; i++) { // Good
+      for (;;) { // ok
+      while (1) { // Better
+</pre>
+    <p>
+      Empty loop bodies are better represented with curly braces and a
+      comment, although use of a semicolon is not currently rejected.
+    </p>
+    <pre>
+      while ((rc = waitpid(pid, &amp;st, 0) == -1) &amp;&amp;
+             errno == EINTR); // ok
+      while ((rc = waitpid(pid, &amp;st, 0) == -1) &amp;&amp;
+             errno == EINTR) { // Better
+          /* nothing */
+      }
+</pre>
+
     <h2><a name="curly_braces">Curly braces</a></h2>
 
     <p>