libpriv: Introduce an rpmostree_mkdtemp()

- Can also give you a file descriptor
 - Takes a constant string as input, returning a mutated string as a
   separate variable which means that one can check whether the variable
   is `NULL` to know whether or not one needs to `rm -rf` it on error
   paths.

src/app/rpmostree-compose-builtin-tree.c

@@ -648,7 +648,11 @@ rpmostree_compose_builtin_tree (int             argc,
     }
   else
     {
-      gs_free char *tmpd = g_mkdtemp (g_strdup ("/var/tmp/rpm-ostree.XXXXXX"));
+      gs_free char *tmpd = NULL;
+
+      if (!rpmostree_mkdtemp ("/var/tmp/rpm-ostree.XXXXXX", &tmpd, NULL, error))
+        goto out;
+
       self->workdir = g_file_new_for_path (tmpd);
       workdir_is_tmp = TRUE;
 

src/libpriv/rpmostree-rpm-util.c

@@ -710,24 +710,16 @@ rpmostree_checkout_only_rpmdb_tempdir (OstreeRepo       *repo,
 {
   gboolean ret = FALSE;
   g_autofree char *commit = NULL;
-  g_autofree char *tempdir = g_strdup ("/tmp/rpmostree-dbquery-XXXXXXXX");
-  gboolean created_tmpdir = FALSE;
+  g_autofree char *tempdir = NULL;
   OstreeRepoCheckoutOptions checkout_options = { 0, };
   glnx_fd_close int tempdir_dfd = -1;
 
   g_return_val_if_fail (out_tempdir != NULL, FALSE);
 
-  if (!ostree_repo_resolve_rev (repo, ref, FALSE, &commit, error))
+  if (!rpmostree_mkdtemp ("/tmp/rpmostree-dbquery-XXXXXX", &tempdir, &tempdir_dfd, error))
     goto out;
 
-  if (mkdtemp (tempdir) == NULL)
-    {
-      glnx_set_error_from_errno (error);
-      goto out;
-    }
-  created_tmpdir = TRUE;
-
-  if (!glnx_opendirat (AT_FDCWD, tempdir, FALSE, &tempdir_dfd, error))
+  if (!ostree_repo_resolve_rev (repo, ref, FALSE, &commit, error))
     goto out;
 
   /* Create intermediate dirs */ 
@@ -753,8 +745,7 @@ rpmostree_checkout_only_rpmdb_tempdir (OstreeRepo       *repo,
       goto out;
     }
 
-  *out_tempdir = tempdir;
-  tempdir = NULL;
+  *out_tempdir = g_steal_pointer (&tempdir);
   if (out_tempdir_dfd)
     {
       *out_tempdir_dfd = tempdir_dfd;
@@ -762,7 +753,7 @@ rpmostree_checkout_only_rpmdb_tempdir (OstreeRepo       *repo,
     }
   ret = TRUE;
  out:
-  if (created_tmpdir && tempdir)
+  if (tempdir)
     (void) glnx_shutil_rm_rf_at (AT_FDCWD, tempdir, NULL, NULL);
   return ret;
 }

src/libpriv/rpmostree-util.c

@@ -28,6 +28,7 @@
 
 #include "rpmostree-util.h"
 #include "libgsystem.h"
+#include "libglnx.h"
 
 void
 _rpmostree_set_error_from_errno (GError    **error,
@@ -65,6 +66,45 @@ _rpmostree_perror_fatal (const char *message)
   exit (1);
 }
 
+gboolean
+rpmostree_mkdtemp (const char   *template,
+                   char        **out_tmpdir,
+                   int          *out_tmpdir_dfd,  /* allow-none */
+                   GError      **error)
+{
+  gboolean ret = FALSE;
+  g_autofree char *tmpdir = g_strdup (template);
+  gboolean created_tmpdir = FALSE;
+  glnx_fd_close int ret_tmpdir_dfd = -1;
+
+  if (mkdtemp (tmpdir) == NULL)
+    {
+      glnx_set_error_from_errno (error);
+      goto out;
+    }
+  created_tmpdir = TRUE;
+
+  if (out_tmpdir_dfd)
+    {
+      if (!glnx_opendirat (AT_FDCWD, tmpdir, FALSE, &ret_tmpdir_dfd, error))
+        goto out;
+    }
+
+  ret = TRUE;
+  *out_tmpdir = g_steal_pointer (&tmpdir);
+  if (out_tmpdir_dfd)
+    {
+      *out_tmpdir_dfd = ret_tmpdir_dfd;
+      ret_tmpdir_dfd = -1;
+    }
+ out:
+  if (created_tmpdir && tmpdir)
+    {
+     (void) glnx_shutil_rm_rf_at (AT_FDCWD, tmpdir, NULL, NULL);
+    }
+  return ret;
+}
+
 gboolean
 _rpmostree_util_enumerate_directory_allow_noent (GFile               *dirpath,
 						 const char          *queryargs,

src/libpriv/rpmostree-util.h

@@ -37,6 +37,11 @@ _rpmostree_set_prefix_error_from_errno (GError     **error,
 
 void _rpmostree_perror_fatal (const char *message) __attribute__ ((noreturn));
 
+gboolean rpmostree_mkdtemp (const char   *template,
+                             char       **out_tmpdir,
+                             int         *out_tmpdir_dfd,  /* allow-none */
+                             GError     **error);
+
 gboolean
 _rpmostree_util_enumerate_directory_allow_noent (GFile               *dirpath,
 						 const char          *queryargs,