Do not segv if NULL is passed for CTX in sendfd and receivefd.

* src/assuan-buffer.c (assuan_sendfd): Check that CTX is not NULL.
(assuan_receivefd): Ditto.
--

This change is to align the behaviour with that of assuan_send_data.

Suggested-by: Andre Heinecke.
Signed-off-by: Werner Koch <wk@gnupg.org>

1 files changed, 4 insertions, 2 deletions

diff --git a/doc/assuan.texi b/doc/assuan.texi
index 358357c..10b309c 100644
--- a/doc/assuan.texi
+++ b/doc/assuan.texi
@@ -1205,8 +1205,10 @@ The descriptor must be sent before the command is issued that makes
 use of the descriptor.
 
 Note that calling this function with a @var{ctx} of @code{NULL} and
-@var{fd} of @code{-1} can be used as a runtime test to check whether
-descriptor passing is available on the platform.  If it is, 0 is returned, otherwise an error with the error code @code{GPG_ERR_NOT_IMPLEMENTED}.
+@var{fd} of @code{ASSUAN_INVALID_FD} can be used as a runtime test to
+check whether descriptor passing is available on the platform:
+@code{0} is returned if descriptor passing is available, otherwise an
+error with the error code @code{GPG_ERR_NOT_IMPLEMENTED} is returned.
 @end deftypefun
 
 @anchor{function assuan_receivefd}