[libglnx] dirfd: Have dfd iter _take_fd() take a pointer and do a steal

[Colin Walters <walters src gnome org>]

commit f5ba01cf65309164adb06067b39cf28c071e1ccb
Author: Colin Walters <walters verbum org>
Date:   Wed May 31 14:48:53 2017 -0400

    dirfd: Have dfd iter _take_fd() take a pointer and do a steal
    
    This avoids callers having to use `glnx_steal_fd()` on their own; in general, I
    think we should implement move semantics like this at the callee level.
    
    Another reason to do this is there's a subtle problem with doing:
    
    ```
    somefunction (steal_value (&v), ..., error);
    ```
    
    in that if `somefunction` throws, it may not have taken ownership of the value.
    At least `glnx_dirfd_iterator_init_take_fd()` didn't.

 glnx-dirfd.c  |   10 +++++-----
 glnx-dirfd.h  |    2 +-
 glnx-shutil.c |    3 +--
 3 files changed, 7 insertions(+), 8 deletions(-)
---
diff --git a/glnx-dirfd.c b/glnx-dirfd.c
index 388f2a3..bb73b01 100644
--- a/glnx-dirfd.c
+++ b/glnx-dirfd.c
@@ -103,7 +103,7 @@ glnx_dirfd_iterator_init_at (int                     dfd,
   if (!glnx_opendirat (dfd, path, follow, &fd, error))
     return FALSE;
 
-  if (!glnx_dirfd_iterator_init_take_fd (glnx_steal_fd (&fd), out_dfd_iter, error))
+  if (!glnx_dirfd_iterator_init_take_fd (&fd, out_dfd_iter, error))
     return FALSE;
 
   return TRUE;
@@ -111,7 +111,7 @@ glnx_dirfd_iterator_init_at (int                     dfd,
 
 /**
  * glnx_dirfd_iterator_init_take_fd:
- * @dfd: File descriptor - ownership is taken
+ * @dfd: File descriptor - ownership is taken, and the value is set to -1
  * @dfd_iter: A directory iterator
  * @error: Error
  *
@@ -119,16 +119,16 @@ glnx_dirfd_iterator_init_at (int                     dfd,
  * iteration.
  */
 gboolean
-glnx_dirfd_iterator_init_take_fd (int                dfd,
+glnx_dirfd_iterator_init_take_fd (int               *dfd,
                                   GLnxDirFdIterator *dfd_iter,
                                   GError           **error)
 {
   GLnxRealDirfdIterator *real_dfd_iter = (GLnxRealDirfdIterator*) dfd_iter;
-  DIR *d = fdopendir (dfd);
+  DIR *d = fdopendir (*dfd);
   if (!d)
     return glnx_throw_errno_prefix (error, "fdopendir");
 
-  real_dfd_iter->fd = dfd;
+  real_dfd_iter->fd = glnx_steal_fd (dfd);
   real_dfd_iter->d = d;
   real_dfd_iter->initialized = TRUE;
 
diff --git a/glnx-dirfd.h b/glnx-dirfd.h
index 0cb79e6..581b303 100644
--- a/glnx-dirfd.h
+++ b/glnx-dirfd.h
@@ -55,7 +55,7 @@ typedef struct GLnxDirFdIterator GLnxDirFdIterator;
 gboolean glnx_dirfd_iterator_init_at (int dfd, const char *path,
                                     gboolean follow,
                                     GLnxDirFdIterator *dfd_iter, GError **error);
-gboolean glnx_dirfd_iterator_init_take_fd (int dfd, GLnxDirFdIterator *dfd_iter, GError **error);
+gboolean glnx_dirfd_iterator_init_take_fd (int *dfd, GLnxDirFdIterator *dfd_iter, GError **error);
 gboolean glnx_dirfd_iterator_next_dent (GLnxDirFdIterator  *dfd_iter,
                                         struct dirent     **out_dent,
                                         GCancellable       *cancellable,
diff --git a/glnx-shutil.c b/glnx-shutil.c
index 6a1cdd4..2e02eea 100644
--- a/glnx-shutil.c
+++ b/glnx-shutil.c
@@ -110,9 +110,8 @@ glnx_shutil_rm_rf_at (int                   dfd,
     }
   else
     {
-      if (!glnx_dirfd_iterator_init_take_fd (target_dfd, &dfd_iter, error))
+      if (!glnx_dirfd_iterator_init_take_fd (&target_dfd, &dfd_iter, error))
         return FALSE;
-      target_dfd = -1;
 
       if (!glnx_shutil_rm_rf_children (&dfd_iter, cancellable, error))
         return FALSE;