[libglnx] fdio: implement glnx_basename from scratch

[Ray Strode <halfline src gnome org>]

commit 03b48a39347041112a36d379d8d3c969372255c6
Author: Ray Strode <rstrode redhat com>
Date:   Fri Nov 10 09:23:15 2017 -0500

    fdio: implement glnx_basename from scratch
    
    At the top of glnx-fdio.h there's this comment:
    
    /* When we include libgen.h because we need
     * dirname() we immediately undefine
     * basename() since libgen.h defines it as
     * a macro to the XDG version which is really
     * broken. */
    
    and then it does #undef basename to try to
    gain access to non-default basename implementation.
    
    The problem is that this trick doesn't work on
    some systems:
    
    ./libglnx/glnx-fdio.h: In function 'glnx_basename':
    ./libglnx/glnx-fdio.h:46:11: error: 'basename'
    undeclared (first use in this function)
       return (basename) (path);
    
    Anyway, basename() is like 3 lines of code to
    implement, so this commit just does that instead
    of relying on glibc for it.

 glnx-fdio.h |   15 ++++++++-------
 1 files changed, 8 insertions(+), 7 deletions(-)
---
diff --git a/glnx-fdio.h b/glnx-fdio.h
index dc93b68..8af54ff 100644
--- a/glnx-fdio.h
+++ b/glnx-fdio.h
@@ -29,12 +29,6 @@
 #include <string.h>
 #include <stdio.h>
 #include <sys/xattr.h>
-/* From systemd/src/shared/util.h */
-/* When we include libgen.h because we need dirname() we immediately
- * undefine basename() since libgen.h defines it as a macro to the XDG
- * version which is really broken. */
-#include <libgen.h>
-#undef basename
 
 #include <glnx-macros.h>
 #include <glnx-errors.h>
@@ -47,7 +41,14 @@ G_BEGIN_DECLS
 static inline
 const char *glnx_basename (const char *path)
 {
-  return (basename) (path);
+  gchar *base;
+
+  base = strrchr (path, G_DIR_SEPARATOR);
+
+  if (base)
+    return base + 1;
+
+  return path;
 }
 
 /* Utilities for standard FILE* */