Dummy implementation of the roff(7) \V (interpolate environment variable)

escape sequence.  This is needed to get \V into the correct parsing
class, ESCAPE_EXPAND.

It is intentional that mandoc(1) output is *not* influenced by environment
variables, so interpolate the name of the variable with some decorating
punctuation rather than interpolating its value.

1 files changed, 8 insertions, 3 deletions

diff --git a/roff.c b/roff.c
index c76be9b8..e89ca000 100644
--- a/roff.c
+++ b/roff.c
@@ -1529,6 +1529,12 @@ roff_expand(struct roff *r, struct buf *buf, int ln, int pos, char ec)
 			ubuf[1] = '\0';
 			res = ubuf;
 			break;
+		case 'V':
+			mandoc_msg(MANDOCERR_UNSUPP, ln, iesc,
+			    "%.*s", iend - iesc, buf->buf + iesc);
+			roff_expand_patch(buf, iendarg, "}", iend);
+			roff_expand_patch(buf, iesc, "${", iarg);
+			continue;
 		case 'n':
 			if (iendarg > iarg)
 				(void)snprintf(ubuf, sizeof(ubuf), "%d",
@@ -1567,9 +1573,8 @@ roff_expand_patch(struct buf *buf, int start, const char *repl, int end)
 {
 	char	*nbuf;
 
-	buf->buf[start] = '\0';
-	buf->sz = mandoc_asprintf(&nbuf, "%s%s%s", buf->buf, repl,
-	    buf->buf + end) + 1;
+	buf->sz = mandoc_asprintf(&nbuf, "%.*s%s%s", start, buf->buf,
+	    repl, buf->buf + end) + 1;
 	free(buf->buf);
 	buf->buf = nbuf;
 }