[PATCH] support for obtaining file basename

[Robert Millan <rmh at aybabtu dot com>]

Please consider this patch.  It adds support for obtaining file basename via
__FILE_BASENAME__.

This would be used by GNU GRUB.  I'll provide some explanation on why this is
very necessary for us:

  - Bootloader code is very critical; a bug can render system unbootable. 
Additionally, it needs to support a wide range of hardware and firmware. 
Because of this, we put extensive debugging support into GRUB.  Debug
statements currently rely on __FILE__.

  - We want to support $srcdir != $objdir build setups, and continue supporting
them.

  - Some parts of bootstrap code tend to be very size constrained.  Every byte
counts, and each debug statement is taking unnecessary space because accessing
a file in $srcdir requires either an absolute path or at least a number of
'../' components (in Debian, that would be two of them).

Because of this, I would find it very useful if GCC provided __FILE_BASENAME__,
or at least an equivalent facility.


Also filed as: http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42579

-- 
Robert Millan

  "Be the change you want to see in the world" -- Gandhi

2010-01-02  Robert Millan  <rmh.grub@aybabtu.com>

	Support for obtaining file basename via __FILE_BASENAME__.

	* include/cpplib.h (cpp_builtin_type): Add `BT_FILE_BASENAME'.
	* init.c (builtin_array): Add entry for `__FILE_BASENAME__'.
	* macro.c (_cpp_builtin_macro_text): Recognize and act upon
	`BT_FILE_BASENAME'.

diff -urp libcpp.old/include/cpplib.h libcpp/include/cpplib.h
--- libcpp.old/include/cpplib.h	2010-01-02 10:53:42.000000000 +0100
+++ libcpp/include/cpplib.h	2010-01-01 21:05:56.000000000 +0100
@@ -595,6 +595,7 @@ enum cpp_builtin_type
   BT_SPECLINE = 0,		/* `__LINE__' */
   BT_DATE,			/* `__DATE__' */
   BT_FILE,			/* `__FILE__' */
+  BT_FILE_BASENAME,		/* `__FILE_BASENAME__' */
   BT_BASE_FILE,			/* `__BASE_FILE__' */
   BT_INCLUDE_LEVEL,		/* `__INCLUDE_LEVEL__' */
   BT_TIME,			/* `__TIME__' */
diff -urp libcpp.old/init.c libcpp/init.c
--- libcpp.old/init.c	2010-01-02 10:53:42.000000000 +0100
+++ libcpp/init.c	2010-01-01 21:05:56.000000000 +0100
@@ -344,6 +344,7 @@ static const struct builtin_macro builti
   B("__TIME__",		 BT_TIME,          false),
   B("__DATE__",		 BT_DATE,          false),
   B("__FILE__",		 BT_FILE,          false),
+  B("__FILE_BASENAME__", BT_FILE_BASENAME, false),
   B("__BASE_FILE__",	 BT_BASE_FILE,     false),
   B("__LINE__",		 BT_SPECLINE,      true),
   B("__INCLUDE_LEVEL__", BT_INCLUDE_LEVEL, true),
diff -urp libcpp.old/macro.c libcpp/macro.c
--- libcpp.old/macro.c	2010-01-02 10:53:42.000000000 +0100
+++ libcpp/macro.c	2010-01-01 21:05:56.000000000 +0100
@@ -1,7 +1,7 @@
 /* Part of CPP library.  (Macro and #define handling.)
    Copyright (C) 1986, 1987, 1989, 1992, 1993, 1994, 1995, 1996, 1998,
    1999, 2000, 2001, 2002, 2003, 2004, 2005,
-   2006, 2007, 2008, 2009 Free Software Foundation, Inc.
+   2006, 2007, 2008, 2009, 2010 Free Software Foundation, Inc.
    Written by Per Bothner, 1994.
    Based on CCCP program by Paul Rubin, June 1986
    Adapted to ANSI C, Richard Stallman, Jan 1987
@@ -166,6 +166,7 @@ _cpp_builtin_macro_text (cpp_reader *pfi
       }
       break;
     case BT_FILE:
+    case BT_FILE_BASENAME:
     case BT_BASE_FILE:
       {
 	unsigned int len;
@@ -178,6 +179,10 @@ _cpp_builtin_macro_text (cpp_reader *pfi
 	    map = INCLUDED_FROM (pfile->line_table, map);
 
 	name = map->to_file;
+
+	if (node->value.builtin == BT_FILE_BASENAME)
+	  name = basename (name);
+
 	len = strlen (name);
 	buf = _cpp_unaligned_alloc (pfile, len * 2 + 3);
 	result = buf;