In case an ID attribute is written in pieces, only protect the first

piece with a prepended 'x', not each piece, such that quoted and
unquoted .Sh, .Ss, and .Sx arguments are compatible with each other.
Fixing a bug reported by Nicolas Joly <njoly at NetBSD dot org>,
avoiding a regression in my first patch as pointed out by njoly as well.
"feel free to do so" kristaps@

1 files changed, 13 insertions, 9 deletions

diff --git a/html.c b/html.c
index 98ce7735..d82cec3c 100644
--- a/html.c
+++ b/html.c
@@ -771,20 +771,24 @@ html_idcat(char *dst, const char *src, int sz)
 {
 	int		 ssz;
 
-	assert(sz);
+	assert(sz > 2);
 
 	/* Cf. <http://www.w3.org/TR/html4/types.html#h-6.2>. */
 
-	for ( ; *dst != '\0' && sz; dst++, sz--)
-		/* Jump to end. */ ;
-
-	assert(sz > 2);
-
 	/* We can't start with a number (bah). */
 
-	*dst++ = 'x';
-	*dst = '\0';
-	sz--;
+	if ('#' == *dst) {
+		dst++;
+		sz--;
+	}
+	if ('\0' == *dst) {
+		*dst++ = 'x';
+		*dst = '\0';
+		sz--;
+	}
+
+	for ( ; *dst != '\0' && sz; dst++, sz--)
+		/* Jump to end. */ ;
 
 	for ( ; *src != '\0' && sz > 1; src++) {
 		ssz = snprintf(dst, (size_t)sz, "%.2x", *src);