HTTP: empty chunked POST ended up in two zero size chunks

When doing a chunked-encoded POST with -d (CURLOPT_POSTFIELDS) and the
size of the POST was zero length, it made libcurl first send a zero
chunk and then the terminating one. This could confuse a receiver and it
should rather just send the terminating chunk as it does with this fix.

Test case 1333 is added to verify.

Bug: http://curl.haxx.se/mail/archive-2012-04/0060.html
Reported by: Arnaud Compan

lib/http.c

@@ -1088,7 +1088,7 @@ CURLcode Curl_add_buffer_send(Curl_send_buffer *in,
     if(conn->data->set.verbose) {
       /* this data _may_ contain binary stuff */
       Curl_debug(conn->data, CURLINFO_HEADER_OUT, ptr, headlen, conn);
-      if((size_t)amount > headlen) {
+      if(bodylen) {
         /* there was body data sent beyond the initial header part, pass that
            on to the debug callback too */
         Curl_debug(conn->data, CURLINFO_DATA_OUT,
@@ -2480,11 +2480,13 @@ CURLcode Curl_http(struct connectdata *conn, bool *done)
           included_body = postsize;
         }
         else {
-          /* Append the POST data chunky-style */
-          result = Curl_add_bufferf(req_buffer, "%x\r\n", (int)postsize);
-          if(CURLE_OK == result)
-            result = Curl_add_buffer(req_buffer, data->set.postfields,
-                                     (size_t)postsize);
+          if(postsize) {
+            /* Append the POST data chunky-style */
+            result = Curl_add_bufferf(req_buffer, "%x\r\n", (int)postsize);
+            if(CURLE_OK == result)
+              result = Curl_add_buffer(req_buffer, data->set.postfields,
+                                       (size_t)postsize);
+          }
           if(CURLE_OK == result)
             result = Curl_add_buffer(req_buffer,
                                      "\x0d\x0a\x30\x0d\x0a\x0d\x0a", 7);

tests/data/Makefile.am

@@ -83,7 +83,7 @@ test1300 test1301 test1302 test1303 test1304 test1305	\
 test1306 test1307 test1308 test1309 test1310 test1311 test1312 test1313 \
 test1314 test1315 test1316 test1317 test1318 test1319 test1320 test1321 \
 test1322 test1323 test1324 test1325 test1326 test1327 test1328 test1329 \
-test1331 test1332 \
+test1331 test1332 test1333 \
 test1400 test1401 test1402 test1403 test1404 test1405 test1406 test1407 \
 test2000 test2001 test2002 test2003 test2004
 

tests/data/test1333

@@ -0,0 +1,55 @@
+<testcase>
+<info>
+<keywords>
+HTTP
+HTTP GET
+</keywords>
+</info>
+
+#
+# Server-side
+<reply>
+<data>
+HTTP/1.1 200 OK
+Date: Thu, 09 Nov 2010 14:49:00 GMT
+Accept-Ranges: bytes
+Content-Length: 6
+Connection: close
+
+-foo-
+</data>
+</reply>
+
+#
+# Client-side
+<client>
+<server>
+http
+</server>
+ <name>
+HTTP POST zero length, chunked-encoded
+ </name>
+ <command>
+-d "" --header "Transfer-Encoding: chunked" http://%HOSTIP:%HTTPPORT/1333
+</command>
+</client>
+
+#
+# Verify data after the test has been "shot"
+<verify>
+<strip>
+^User-Agent:.*
+</strip>
+<protocol>
+POST /1333 HTTP/1.1
+Host: %HOSTIP:%HTTPPORT
+Accept: */*
+Transfer-Encoding: chunked
+Content-Type: application/x-www-form-urlencoded
+
+
+0
+
+</protocol>
+</verify>
+</testcase>