[sysprof] writer: use dup()d fd when creating reader

[Christian Hergert <chergert src gnome org>]

commit 1b8cfed5c880d1fdc9c0d71412d918b14aebabb5
Author: Christian Hergert <christian hergert me>
Date:   Thu Apr 14 19:25:26 2016 -0700

    writer: use dup()d fd when creating reader
    
    Readers can share the file-offset in the file-descriptor table, but should
    really have their own fd that they can close().

 lib/sp-capture-writer.c |   11 ++++++++++-
 1 files changed, 10 insertions(+), 1 deletions(-)
---
diff --git a/lib/sp-capture-writer.c b/lib/sp-capture-writer.c
index 794fa38..b416c57 100644
--- a/lib/sp-capture-writer.c
+++ b/lib/sp-capture-writer.c
@@ -933,10 +933,19 @@ SpCaptureReader *
 sp_capture_writer_create_reader (SpCaptureWriter  *self,
                                  GError          **error)
 {
+  int copy;
+
   g_return_val_if_fail (self != NULL, NULL);
   g_return_val_if_fail (self->fd != -1, NULL);
 
-  return sp_capture_reader_new_from_fd (self->fd, error);
+  /*
+   * We don't care about the write position, since the reader
+   * uses positioned reads.
+   */
+  if (-1 == (copy = dup (self->fd)))
+    return NULL;
+
+  return sp_capture_reader_new_from_fd (copy, error);
 }
 
 /**