[glib] Return NULL from g_mapped_file_get_contents()

[Ryan Lortie <ryanl src gnome org>]

commit b0a0ac51cb7e628f90b8293c098a6a1a26425301
Author: Ryan Lortie <desrt desrt ca>
Date:   Wed Jan 27 21:30:26 2010 -0500

    Return NULL from g_mapped_file_get_contents()
    
    In the case of an empty file, return NULL instead of "".  This means
    that the return result of g_mapped_file_get_contents() will always be
    page-aligned.

 README.in          |    5 +++++
 glib/gmappedfile.c |    6 ++++--
 2 files changed, 9 insertions(+), 2 deletions(-)
---
diff --git a/README.in b/README.in
index 52707f7..94a3c2a 100644
--- a/README.in
+++ b/README.in
@@ -39,6 +39,11 @@ Notes about GLib 2.24
   while an object is being initialized. If this behavior is needed, setting a
   custom constructor that just chains up will re-enable this functionality.
 
+* GMappedFile on an empty file now returns NULL for the contents instead of
+  returning an empty string. The documentation specifically states that code
+  may not rely on nul-termination here so any breakage caused by this change
+  is a bug in application code.
+
 Notes about GLib 2.22
 =====================
 
diff --git a/glib/gmappedfile.c b/glib/gmappedfile.c
index 77865b8..347f964 100644
--- a/glib/gmappedfile.c
+++ b/glib/gmappedfile.c
@@ -148,7 +148,7 @@ g_mapped_file_new (const gchar  *filename,
   if (st.st_size == 0)
     {
       file->length = 0;
-      file->contents = "";
+      file->contents = NULL;
       close (fd);
       return file;
     }
@@ -242,7 +242,9 @@ g_mapped_file_get_length (GMappedFile *file)
  * Note that the contents may not be zero-terminated,
  * even if the #GMappedFile is backed by a text file.
  *
- * Returns: the contents of @file.
+ * If the file is empty then %NULL is returned.
+ *
+ * Returns: the contents of @file, or %NULL.
  *
  * Since: 2.8
  */