[Libguestfs] [PATCH nbdkit] Fix --dump-plugin on perl, python and ruby plugins.

[Richard W.M. Jones]

Previously doing:

  nbdkit python --dump-plugin

would segfault since the script was not loaded.  It was possible to
work around this using:

  nbdkit python test.py --dump-plugin

assuming that you had a Python script to use.

Change the code so that the original command (without the script name)
doesn't segfault.
---
 plugins/perl/perl.c     | 2 +-
 plugins/python/python.c | 2 +-
 plugins/ruby/ruby.c     | 4 +---
 3 files changed, 3 insertions(+), 5 deletions(-)

diff --git a/plugins/perl/perl.c b/plugins/perl/perl.c
index 80e5695..8d35b85 100644
--- a/plugins/perl/perl.c
+++ b/plugins/perl/perl.c
@@ -169,7 +169,7 @@ perl_dump_plugin (void)
 {
   dSP;
 
-  if (callback_defined ("dump_plugin")) {
+  if (script && callback_defined ("dump_plugin")) {
     ENTER;
     SAVETMPS;
     PUSHMARK (SP);
diff --git a/plugins/python/python.c b/plugins/python/python.c
index b105e53..83a32ea 100644
--- a/plugins/python/python.c
+++ b/plugins/python/python.c
@@ -155,7 +155,7 @@ py_dump_plugin (void)
   PyObject *fn;
   PyObject *r;
 
-  if (callback_defined ("dump_plugin", &fn)) {
+  if (script && callback_defined ("dump_plugin", &fn)) {
     PyErr_Clear ();
 
     r = PyObject_CallObject (fn, NULL);
diff --git a/plugins/ruby/ruby.c b/plugins/ruby/ruby.c
index 6b0285f..aa57f65 100644
--- a/plugins/ruby/ruby.c
+++ b/plugins/ruby/ruby.c
@@ -168,10 +168,8 @@ plugin_rb_unload (void)
 static void
 plugin_rb_dump_plugin (void)
 {
-  if (!script) {
-    nbdkit_error ("the first parameter must be script=/path/to/ruby/script.rb");
+  if (!script)
     return;
-  }
 
   assert (code != NULL);
 
-- 
2.13.2