[Libguestfs] [PATCH 3/3] python: Allow bindings to be compiled with different version of libguestfs (RHBZ#1262983).

[Richard W.M. Jones]

When compiling the libguestfs bindings as a pip module, it's helpful
if you can compile the bindings with a different version of libguestfs
(eg. installed 1.28, pip module 1.30).

That broke the previous assumption that we were always compiling
against precisely the same version of libguestfs (which made sense
because the python bindings are part of the libguestfs source tree).

Python distutils has no way to check a C library to find out if
functions are defined.  Therefore we have to rely on GUESTFS_HAVE_*
macros from <guestfs.h>.
---
 generator/python.ml | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/generator/python.ml b/generator/python.ml
index 637f22d..c1128f8 100644
--- a/generator/python.ml
+++ b/generator/python.ml
@@ -140,6 +140,7 @@ put_table (char * const * const argv)
 ";
 
   let emit_put_list_function typ =
+    pr "#ifdef GUESTFS_HAVE_STRUCT_%s\n" (String.uppercase typ);
     pr "static PyObject *\n";
     pr "put_%s_list (struct guestfs_%s_list *%ss)\n" typ typ typ;
     pr "{\n";
@@ -151,12 +152,14 @@ put_table (char * const * const argv)
     pr "    PyList_SetItem (list, i, put_%s (&%ss->val[i]));\n" typ typ;
     pr "  return list;\n";
     pr "};\n";
+    pr "#endif\n";
     pr "\n"
   in
 
   (* Structures, turned into Python dictionaries. *)
   List.iter (
     fun { s_name = typ; s_cols = cols } ->
+      pr "#ifdef GUESTFS_HAVE_STRUCT_%s\n" (String.uppercase typ);
       pr "static PyObject *\n";
       pr "put_%s (struct guestfs_%s *%s)\n" typ typ typ;
       pr "{\n";
@@ -228,6 +231,7 @@ put_table (char * const * const argv)
       ) cols;
       pr "  return dict;\n";
       pr "};\n";
+      pr "#endif\n";
       pr "\n";
 
   ) external_structs;
@@ -246,6 +250,7 @@ put_table (char * const * const argv)
     fun { name = name; style = (ret, args, optargs as style);
           blocking = blocking;
           c_function = c_function; c_optarg_prefix = c_optarg_prefix } ->
+      pr "#ifdef GUESTFS_HAVE_%s\n" (String.uppercase name);
       pr "static PyObject *\n";
       pr "py_guestfs_%s (PyObject *self, PyObject *args)\n" name;
       pr "{\n";
@@ -381,6 +386,7 @@ put_table (char * const * const argv)
           fun optarg ->
             let n = name_of_optargt optarg in
             let uc_n = String.uppercase n in
+            pr "#ifdef %s_%s_BITMASK\n" c_optarg_prefix uc_n;
             pr "  if (py_%s != Py_None) {\n" n;
             pr "    optargs_s.bitmask |= %s_%s_BITMASK;\n" c_optarg_prefix uc_n;
             (match optarg with
@@ -403,6 +409,7 @@ put_table (char * const * const argv)
               pr "    if (!optargs_s.%s) goto out;\n" n;
             );
             pr "  }\n";
+            pr "#endif\n"
         ) optargs;
         pr "\n"
       );
@@ -524,13 +531,16 @@ put_table (char * const * const argv)
         | OBool _ | OInt _ | OInt64 _ | OString _ -> ()
         | OStringList n ->
           let uc_n = String.uppercase n in
+          pr "#ifdef %s_%s_BITMASK\n" c_optarg_prefix uc_n;
           pr "  if (py_%s != Py_None && (optargs_s.bitmask & %s_%s_BITMASK) != 0)\n"
             n c_optarg_prefix uc_n;
-          pr "    free ((char **) optargs_s.%s);\n" n
+          pr "    free ((char **) optargs_s.%s);\n" n;
+          pr "#endif\n"
       ) optargs;
 
       pr "  return py_r;\n";
       pr "}\n";
+      pr "#endif\n";
       pr "\n"
   ) external_functions_sorted;
 
@@ -546,8 +556,10 @@ put_table (char * const * const argv)
   pr "    py_guestfs_event_to_string, METH_VARARGS, NULL },\n";
   List.iter (
     fun { name = name } ->
+      pr "#ifdef GUESTFS_HAVE_%s\n" (String.uppercase name);
       pr "  { (char *) \"%s\", py_guestfs_%s, METH_VARARGS, NULL },\n"
-        name name
+        name name;
+      pr "#endif\n"
   ) external_functions_sorted;
   pr "  { NULL, NULL, 0, NULL }\n";
   pr "};\n";
-- 
2.5.0