[patch] basename vs. __gnu_basename fix

[Corinna Vinschen <vinschen at redhat dot com>]

Hi,

I'd like to propose the following patch.  While running some autoconf
script under a test version of Cygwin, the following problem turned up:

In file included from conftest.c:429:0:
/usr/include/libgen.h:18:14: error: conflicting types for 'basename'
 extern char *basename (char *path);
              ^
In file included from /usr/include/stdio.h:29:0,
                 from conftest.c:396:
/usr/include/string.h:172:7: note: previous declaration of 'basename' was here
 char *_EXFUN(basename,(const char *))
       ^

It turns out that the current method to define basename in libgen.h
(POSIX) as well as in string.h (GNU) is prone to an ordering problem.  I
checked that this problem doesn't exist with glibc, and that the glibc
method prefers the POSIX version over the GNU version if libgen.h is
included, independently of the order of inclusion.

However, this is a bit simpler in glibc because the symbol "basename"
is the GNU version and "__xpg_basename" is the POSIX version and
__xpg_basename is preferred by simply having 

  #define basename __xpg_basename

in libgen.h.

The below patch emulates the way glibc does it.  I tested it locally
on a Cygwin installation, but I wouldn't be too unhappy for some
scrutinizing look.


Thanks,
Corinna


	* libc/include/libgen.h: Drop defining _BASENAME_DEFINED.  Always
	define macro basename.  Add comment to explain why.
	* libc/include/string.h: Check for basename instead of
	_BASENAME_DEFINED.  Drop __GNUC__ branch and always use basename
	macro instead.  Change comment to explain why.


diff --git a/newlib/libc/include/libgen.h b/newlib/libc/include/libgen.h
index 8360a22..292d585 100644
--- a/newlib/libc/include/libgen.h
+++ b/newlib/libc/include/libgen.h
@@ -12,8 +12,14 @@
 extern "C" {
 #endif
 
+/* There are two common basename variants.  If you #include <libgen.h> you get
+   the POSIX version; otherwise, if you define _GNU_SOURCE, you get the GNU
+   version via <string.h>.  POSIX requires that #undef basename will still let
+   you invoke the underlying function.  However, this also implies that the
+   POSIX version is used in this case.  That's made sure here. */
+#undef basename
+#define basename basename
 char      *_EXFUN(basename,     (char *));
-#define _BASENAME_DEFINED
 char      *_EXFUN(dirname,     (char *));
 
 #ifdef __cplusplus
diff --git a/newlib/libc/include/string.h b/newlib/libc/include/string.h
index 9e11e5c..cee9bd9 100644
--- a/newlib/libc/include/string.h
+++ b/newlib/libc/include/string.h
@@ -163,18 +163,14 @@ int	_EXFUN(strtosigno, (const char *__name));
 			 (char *) memcpy (__out, __in, __len-1);}))
 #endif /* _GNU_SOURCE && __GNUC__ */
 
-/* There are two common basename variants.  If you #include <libgen.h>
-   first, you get the POSIX version; otherwise you get the GNU version.
-   POSIX requires that #undef basename will still let you
-   invoke the underlying function, but that requires gcc support.  */
-#if __GNU_VISIBLE && !defined(_BASENAME_DEFINED)
-# ifdef __GNUC__
-char	*_EXFUN(basename,(const char *))
-             __asm__ (__ASMNAME ("__gnu_basename")) __nonnull(1);
-# else
+/* There are two common basename variants.  If you #include <libgen.h> you get
+   the POSIX version; otherwise, if you define _GNU_SOURCE, you get the GNU
+   version via <string.h>.  POSIX requires that #undef basename will still let
+   you invoke the underlying function.  However, this also implies that the
+   POSIX version is used in this case.  That's made sure here. */
+#if __GNU_VISIBLE && !defined(basename)
 char	*_EXFUN(__gnu_basename,(const char *));
 # define basename __gnu_basename
-# endif
 #endif
 
 #include <sys/string.h>


-- 
Corinna Vinschen
Cygwin Maintainer
Red Hat

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