[glib] MacOS: create_cstr_from_cfstring uses safe conversion - use CFStringGetCString

[Philip Withnall <pwithnall src gnome org>]

commit 2bd423c54c4793784059f983b6269a51e073cda9
Author: Friedrich Beckmann <friedrich beckmann gmx de>
Date:   Sun Oct 15 13:16:44 2017 +0200

    MacOS: create_cstr_from_cfstring uses safe conversion - use CFStringGetCString
    
    During testing with gdk-pixbuf I noticed failures during content type
    to mime conversion. The root reason was the unsafe conversion used
    in create_cstr_from_cfstring. The problem was addressed in commit
    c60226e0a1cae40a96 but that was reverted. I noticed the commit only
    when I had fixed the problem. In addition I added a test to check
    the content type to mime conversion on MacOS. This problem is
    discussed in Bug #788936.
    
    See: https://bugzilla.gnome.org/show_bug.cgi?id=788936

 gio/gosxappinfo.c       |   25 ++++++++++++++++---------
 gio/gosxcontenttype.c   |   20 +++++++++++++-------
 gio/tests/contenttype.c |   28 ++++++++++++++++++++++++++++
 3 files changed, 57 insertions(+), 16 deletions(-)
---
diff --git a/gio/gosxappinfo.c b/gio/gosxappinfo.c
index b24b6ff..50c1ec3 100644
--- a/gio/gosxappinfo.c
+++ b/gio/gosxappinfo.c
@@ -171,19 +171,26 @@ create_cfstring_from_cstr (const gchar *cstr)
   return CFStringCreateWithCString (NULL, cstr, kCFStringEncodingUTF8);
 }
 
+#ifdef G_ENABLE_DEBUG
 static gchar *
 create_cstr_from_cfstring (CFStringRef str)
 {
-  const gchar *cstr;
+  g_return_val_if_fail (str != NULL, NULL);
 
-  if (str == NULL)
-    return NULL;
-
-  cstr = CFStringGetCStringPtr (str, kCFStringEncodingUTF8);
-  CFRelease (str);
-
-  return g_strdup (cstr);
+  CFIndex length = CFStringGetLength (str);
+  CFIndex maxlen = CFStringGetMaximumSizeForEncoding (length, kCFStringEncodingUTF8);
+  gchar *buffer = g_malloc (maxlen + 1);
+  Boolean success = CFStringGetCString (str, (char *) buffer, maxlen,
+                                        kCFStringEncodingUTF8);
+  if (success)
+    return buffer;
+  else
+    {
+      g_free (buffer);
+      return NULL;
+    }
 }
+#endif
 
 static char *
 url_escape_hostname (const char *url)
diff --git a/gio/gosxcontenttype.c b/gio/gosxcontenttype.c
index 89245d1..604a1ed 100644
--- a/gio/gosxcontenttype.c
+++ b/gio/gosxcontenttype.c
@@ -58,15 +58,21 @@ create_cfstring_from_cstr (const gchar *cstr)
 static gchar *
 create_cstr_from_cfstring (CFStringRef str)
 {
-  const gchar *cstr;
+  g_return_val_if_fail (str != NULL, NULL);
 
-  if (str == NULL)
-    return NULL;
-
-  cstr = CFStringGetCStringPtr (str, kCFStringEncodingUTF8);
+  CFIndex length = CFStringGetLength (str);
+  CFIndex maxlen = CFStringGetMaximumSizeForEncoding (length, kCFStringEncodingUTF8);
+  gchar *buffer = g_malloc (maxlen + 1);
+  Boolean success = CFStringGetCString (str, (char *) buffer, maxlen,
+                                        kCFStringEncodingUTF8);
   CFRelease (str);
-
-  return g_strdup (cstr);
+  if (success)
+    return buffer;
+  else
+    {
+      g_free (buffer);
+      return NULL;
+    }
 }
 
 /*< internal >
diff --git a/gio/tests/contenttype.c b/gio/tests/contenttype.c
index 3589b12..a0da5f6 100644
--- a/gio/tests/contenttype.c
+++ b/gio/tests/contenttype.c
@@ -361,6 +361,33 @@ test_guess_svg_from_data (void)
   g_free (res);
 }
 
+static void
+test_mime_from_content (void)
+{
+#ifdef __APPLE__
+  gchar *mime_type;
+  mime_type = g_content_type_get_mime_type ("com.microsoft.bmp");
+  g_assert_cmpstr (mime_type, ==, "image/bmp");
+  g_free (mime_type);
+  mime_type = g_content_type_get_mime_type ("com.compuserve.gif");
+  g_assert_cmpstr (mime_type, ==, "image/gif");
+  g_free (mime_type);
+  mime_type = g_content_type_get_mime_type ("public.png");
+  g_assert_cmpstr (mime_type, ==, "image/png");
+  g_free (mime_type);
+  mime_type = g_content_type_get_mime_type ("public.text");
+  g_assert_cmpstr (mime_type, ==, "text/*");
+  g_free (mime_type);
+  mime_type = g_content_type_get_mime_type ("public.svg-image");
+  g_assert_cmpstr (mime_type, ==, "image/svg+xml");
+  g_free (mime_type);
+#elif defined(G_OS_WIN32)
+  g_test_skip ("mime from content type test not implemented on WIN32");
+#else
+  g_test_skip ("mime from content type test not implemented on UNIX");
+#endif
+}
+
 int
 main (int argc, char *argv[])
 {
@@ -370,6 +397,7 @@ main (int argc, char *argv[])
 
   g_test_add_func ("/contenttype/guess", test_guess);
   g_test_add_func ("/contenttype/guess_svg_from_data", test_guess_svg_from_data);
+  g_test_add_func ("/contenttype/mime_from_content", test_mime_from_content);
   g_test_add_func ("/contenttype/unknown", test_unknown);
   g_test_add_func ("/contenttype/subtype", test_subtype);
   g_test_add_func ("/contenttype/list", test_list);