GUACAMOLE-1181: Merge rely on automatic freeing of wStream only for FreeRDP 2.0.0-rc3 through 2.0.0-rc4.

configure.ac

@@ -623,7 +623,35 @@ then
 
 fi
 
-# Variation in memory internal allocation/free behavior
+# It is difficult or impossible to test for variations in FreeRDP behavior in
+# between releases, as the change in behavior may not (yet) be associated with
+# a corresponding change in version number and may not have any detectable
+# effect on the FreeRDP API
+if test "x${have_freerdp2}" = "xyes"
+then
+
+    AC_MSG_CHECKING([whether FreeRDP appears to be a development version])
+    AC_EGREP_CPP([\"[0-9]+\\.[0-9]+\\.[0-9]+(-rc[0-9]+)?\"], [
+
+        #include <freerdp/version.h>
+        FREERDP_VERSION_FULL
+
+    ],
+    [AC_MSG_RESULT([no])],
+    [AC_MSG_RESULT([yes])]
+    [AC_MSG_WARN([
+  --------------------------------------------
+   You are building against a development version of FreeRDP. Non-release
+   versions of FreeRDP may have differences in behavior that are impossible to
+   check for at build time. This may result in memory leaks or other strange
+   behavior.
+
+   *** PLEASE USE A RELEASED VERSION OF FREERDP IF POSSIBLE ***
+  --------------------------------------------])])
+
+fi
+
+# Variation in memory internal allocation/free behavior for bitmaps
 if test "x${have_freerdp2}" = "xyes"
 then
 
@@ -647,6 +675,29 @@ then
 
 fi
 
+# Variation in memory internal allocation/free behavior for channel streams
+if test "x${have_freerdp2}" = "xyes"
+then
+
+    # FreeRDP 2.0.0-rc3 through 2.0.0-rc4 automatically free the wStream
+    # provided to pVirtualChannelWriteEx(). This changed in commit 1b78b59, and
+    # implementations must manually free the wStream after it is no longer
+    # needed (after the write is complete or cancelled).
+    AC_MSG_CHECKING([whether pVirtualChannelWriteEx() frees the wStream upon completion])
+    AC_EGREP_CPP([\"2\\.0\\.0-(rc|dev)[3-4]\"], [
+
+        #include <freerdp/version.h>
+        FREERDP_VERSION_FULL
+
+    ],
+    [AC_MSG_RESULT([yes])]
+    [AC_DEFINE([FREERDP_SVC_CORE_FREES_WSTREAM],,
+               [Whether pVirtualChannelWriteEx() frees the wStream upon completion])],
+    [AC_MSG_RESULT([no])])
+
+fi
+
+
 # Glyph callback variants
 if test "x${have_freerdp2}" = "xyes"
 then

src/protocols/rdp/channels/common-svc.c

@@ -89,10 +89,9 @@ void guac_rdp_common_svc_write(guac_rdp_common_svc* svc,
         return;
     }
 
-    /* NOTE: Data sent via pVirtualChannelWriteEx MUST always be dynamically
-     * allocated, as it will be automatically freed using free(). If provided,
-     * the last parameter (user data) MUST be a pointer to a wStream, as it
-     * will automatically be freed by FreeRDP using Stream_Free() */
+    /* NOTE: The wStream sent via pVirtualChannelWriteEx will automatically be
+     * freed later with a call to Stream_Free() when handling the
+     * corresponding write cancel/completion event. */
     svc->_entry_points.pVirtualChannelWriteEx(svc->_init_handle,
             svc->_open_handle, Stream_Buffer(output_stream),
             Stream_GetPosition(output_stream), output_stream);

src/protocols/rdp/plugins/guac-common-svc/guac-common-svc.c

@@ -28,10 +28,8 @@
 #include <stdlib.h>
 
 /**
- * Event handler for events which deal with data transmitted over an open SVC.
- * This specific implementation of the event handler currently handles only the
- * CHANNEL_EVENT_DATA_RECEIVED event, delegating actual handling of that event
- * to guac_rdp_common_svc_process_receive().
+ * Event handler for events which deal with data transmitted over an open SVC,
+ * including receipt of inbound data and completion of outbound writes.
  *
  * The FreeRDP requirements for this function follow those of the
  * VirtualChannelOpenEventEx callback defined within Microsoft's RDP API:
@@ -83,6 +81,15 @@ static VOID guac_rdp_common_svc_handle_open_event(LPVOID user_param,
         DWORD open_handle, UINT event, LPVOID data, UINT32 data_length,
         UINT32 total_length, UINT32 data_flags) {
 
+#ifndef FREERDP_SVC_CORE_FREES_WSTREAM
+    /* Free stream data after send is complete */
+    if ((event == CHANNEL_EVENT_WRITE_CANCELLED
+            || event == CHANNEL_EVENT_WRITE_COMPLETE) && data != NULL) {
+        Stream_Free((wStream*) data, TRUE);
+        return;
+    }
+#endif
+
     /* Ignore all events except for received data */
     if (event != CHANNEL_EVENT_DATA_RECEIVED)
         return;