Remove _G_USING_THUNKS

["Joseph S. Myers" <joseph at codesourcery dot com>]

The macro _G_USING_THUNKS is defined in both versions of _G_config.h
that are used by current configurations, but not in
sysdeps/generic/_G_config.h.  It is used in libio to choose between
two structure layouts, as a relic of the old support for compatibility
with C++ vtables.

I don't think there's any need for libio to have two ways to configure
this implementation detail.  This patch makes it unconditionally use
the _G_USING_THUNKS version, as used with Linux and Hurd, removing the
other alternative and the macro.  (GNU/kFreeBSD, as in Debian, also
defines _G_USING_THUNKS in its version of _G_config.h, so would also
be unaffected by this change.)

Note: I do not know whether this implementation detail ends up forming
part of the public ABI of glibc or whether we are actually free to
change it in any way we please.

Tested on x86_64 that this does not change any of code generated for
glibc's shared libraries.

(diff -w version of the patch attached.)

2012-09-10  Joseph Myers  <joseph@codesourcery.com>

	* libioP.h [_G_USING_THUNKS]: Make code unconditional.
	[!_G_USING_THUNKS]: Remove conditional code.
	* sysdeps/gnu/_G_config.h (_G_USING_THUNKS): Remove.
	* sysdeps/mach/hurd/_G_config.h (_G_USING_THUNKS): Likewise.

diff --git a/libio/libioP.h b/libio/libioP.h
index c8dbac5..01e8bf8 100644
--- a/libio/libioP.h
+++ b/libio/libioP.h
@@ -109,34 +109,18 @@ extern "C" {
 # define _IO_vtable_offset(THIS) 0
 #endif
 #define _IO_WIDE_JUMPS_FUNC(THIS) _IO_WIDE_JUMPS(THIS)
-#ifdef _G_USING_THUNKS
-# define JUMP_FIELD(TYPE, NAME) TYPE NAME
-# define JUMP0(FUNC, THIS) (_IO_JUMPS_FUNC(THIS)->FUNC) (THIS)
-# define JUMP1(FUNC, THIS, X1) (_IO_JUMPS_FUNC(THIS)->FUNC) (THIS, X1)
-# define JUMP2(FUNC, THIS, X1, X2) (_IO_JUMPS_FUNC(THIS)->FUNC) (THIS, X1, X2)
-# define JUMP3(FUNC, THIS, X1,X2,X3) (_IO_JUMPS_FUNC(THIS)->FUNC) (THIS, X1,X2, X3)
-# define JUMP_INIT(NAME, VALUE) VALUE
-# define JUMP_INIT_DUMMY JUMP_INIT(dummy, 0), JUMP_INIT (dummy2, 0)
-
-# define WJUMP0(FUNC, THIS) (_IO_WIDE_JUMPS_FUNC(THIS)->FUNC) (THIS)
-# define WJUMP1(FUNC, THIS, X1) (_IO_WIDE_JUMPS_FUNC(THIS)->FUNC) (THIS, X1)
-# define WJUMP2(FUNC, THIS, X1, X2) (_IO_WIDE_JUMPS_FUNC(THIS)->FUNC) (THIS, X1, X2)
-# define WJUMP3(FUNC, THIS, X1,X2,X3) (_IO_WIDE_JUMPS_FUNC(THIS)->FUNC) (THIS, X1,X2, X3)
-#else
-/* These macros will change when we re-implement vtables to use "thunks"! */
-# define JUMP_FIELD(TYPE, NAME) struct { short delta1, delta2; TYPE pfn; } NAME
-# define JUMP0(FUNC, THIS) _IO_JUMPS_FUNC(THIS)->FUNC.pfn (THIS)
-# define JUMP1(FUNC, THIS, X1) _IO_JUMPS_FUNC(THIS)->FUNC.pfn (THIS, X1)
-# define JUMP2(FUNC, THIS, X1, X2) _IO_JUMPS_FUNC(THIS)->FUNC.pfn (THIS, X1, X2)
-# define JUMP3(FUNC, THIS, X1,X2,X3) _IO_JUMPS_FUNC(THIS)->FUNC.pfn (THIS, X1,X2,X3)
-# define JUMP_INIT(NAME, VALUE) {0, 0, VALUE}
-# define JUMP_INIT_DUMMY JUMP_INIT(dummy, 0)
-
-# define WJUMP0(FUNC, THIS) _IO_WIDE_JUMPS_FUNC(THIS)->FUNC.pfn (THIS)
-# define WJUMP1(FUNC, THIS, X1) _IO_WIDE_JUMPS_FUNC(THIS)->FUNC.pfn (THIS, X1)
-# define WJUMP2(FUNC, THIS, X1, X2) _IO_WIDE_JUMPS_FUNC(THIS)->FUNC.pfn (THIS, X1, X2)
-# define WJUMP3(FUNC, THIS, X1,X2,X3) _IO_WIDE_JUMPS_FUNC(THIS)->FUNC.pfn (THIS, X1,X2,X3)
-#endif
+#define JUMP_FIELD(TYPE, NAME) TYPE NAME
+#define JUMP0(FUNC, THIS) (_IO_JUMPS_FUNC(THIS)->FUNC) (THIS)
+#define JUMP1(FUNC, THIS, X1) (_IO_JUMPS_FUNC(THIS)->FUNC) (THIS, X1)
+#define JUMP2(FUNC, THIS, X1, X2) (_IO_JUMPS_FUNC(THIS)->FUNC) (THIS, X1, X2)
+#define JUMP3(FUNC, THIS, X1,X2,X3) (_IO_JUMPS_FUNC(THIS)->FUNC) (THIS, X1,X2, X3)
+#define JUMP_INIT(NAME, VALUE) VALUE
+#define JUMP_INIT_DUMMY JUMP_INIT(dummy, 0), JUMP_INIT (dummy2, 0)
+
+#define WJUMP0(FUNC, THIS) (_IO_WIDE_JUMPS_FUNC(THIS)->FUNC) (THIS)
+#define WJUMP1(FUNC, THIS, X1) (_IO_WIDE_JUMPS_FUNC(THIS)->FUNC) (THIS, X1)
+#define WJUMP2(FUNC, THIS, X1, X2) (_IO_WIDE_JUMPS_FUNC(THIS)->FUNC) (THIS, X1, X2)
+#define WJUMP3(FUNC, THIS, X1,X2,X3) (_IO_WIDE_JUMPS_FUNC(THIS)->FUNC) (THIS, X1,X2, X3)
 
 /* The 'finish' function does any final cleaning up of an _IO_FILE object.
    It does not delete (free) it, but does everything else to finalize it.
@@ -299,9 +283,7 @@ typedef void (*_IO_imbue_t) (_IO_FILE *, void *);
 struct _IO_jump_t
 {
     JUMP_FIELD(_G_size_t, __dummy);
-#ifdef _G_USING_THUNKS
     JUMP_FIELD(_G_size_t, __dummy2);
-#endif
     JUMP_FIELD(_IO_finish_t, __finish);
     JUMP_FIELD(_IO_overflow_t, __overflow);
     JUMP_FIELD(_IO_underflow_t, __underflow);
diff --git a/sysdeps/gnu/_G_config.h b/sysdeps/gnu/_G_config.h
index 478dbe1..a0dc659 100644
--- a/sysdeps/gnu/_G_config.h
+++ b/sysdeps/gnu/_G_config.h
@@ -83,7 +83,4 @@ typedef unsigned int _G_uint32_t __attribute__ ((__mode__ (__SI__)));
 
 #define _G_BUFSIZ 8192
 
-/* These are the vtbl details for ELF.  */
-#define _G_USING_THUNKS	1
-
 #endif	/* _G_config.h */
diff --git a/sysdeps/mach/hurd/_G_config.h b/sysdeps/mach/hurd/_G_config.h
index 2f683d4..ae10071 100644
--- a/sysdeps/mach/hurd/_G_config.h
+++ b/sysdeps/mach/hurd/_G_config.h
@@ -82,7 +82,4 @@ typedef unsigned int _G_uint32_t __attribute__ ((__mode__ (__SI__)));
 
 #define _G_BUFSIZ 8192
 
-/* These are the vtbl details for ELF.  */
-#define _G_USING_THUNKS	1
-
 #endif	/* _G_config.h */

-- 
Joseph S. Myers
joseph@codesourcery.com

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