libio: Eliminate _IO_stdin, _IO_stdout, _IO_stderr

These variables are only used to determine if a stdio stream is
a pre-allocated stream, but it is possible to do so by comparing
a FILE * to all pre-allocated stream objects.  As a result, it is
not necessary to keep those pointers in separate variables.

Behavior with symbol interposition is unchanged because _IO_stdin_,
_IO_stdout_, _IO_stderr_ are exported, and refer to objects outside of
libc if symbol interposition or copy relocations are involved.  (The
removed variables _IO_stdin, _IO_stdout, _IO_stderr were not exported,
of course.)

1 files changed, 7 insertions, 11 deletions

diff --git a/libio/oldstdfiles.c b/libio/oldstdfiles.c
index 524e260b7e..2b861cd754 100644
--- a/libio/oldstdfiles.c
+++ b/libio/oldstdfiles.c
@@ -27,11 +27,8 @@
 #include <shlib-compat.h>
 #if SHLIB_COMPAT (libc, GLIBC_2_0, GLIBC_2_1)
 
-/* This file provides definitions of _IO_stdin, _IO_stdout, and _IO_stderr
-   for C code.  Compare stdstreams.cc.
-   (The difference is that here the vtable field is set to 0,
-   so the objects defined are not valid C++ objects.  On the other
-   hand, we don't need a C++ compiler to build this file.) */
+/* This file provides legacy definitions of _IO_stdin_, _IO_stdout_,
+   and _IO_stderr_.  See stdfiles.c for the current definitions.  */
 
 #define _IO_USE_OLD_IO_FILE
 #include "libioP.h"
@@ -78,13 +75,12 @@ _IO_check_libio (void)
   if (&_IO_stdin_used == NULL)
     {
       /* We are using the old one. */
-      _IO_stdin = stdin = (FILE *) &_IO_stdin_;
-      _IO_stdout = stdout = (FILE *) &_IO_stdout_;
-      _IO_stderr = stderr = (FILE *) &_IO_stderr_;
+      stdin = (FILE *) &_IO_stdin_;
+      stdout = (FILE *) &_IO_stdout_;
+      stderr = (FILE *) &_IO_stderr_;
       _IO_list_all = &_IO_stderr_;
-      _IO_stdin->_vtable_offset = _IO_stdout->_vtable_offset =
-	_IO_stderr->_vtable_offset = stdin->_vtable_offset =
-	stdout->_vtable_offset = stderr->_vtable_offset =
+      stdin->_vtable_offset = stdout->_vtable_offset
+	= stderr->_vtable_offset =
 	((int) sizeof (struct _IO_FILE)
 	 - (int) sizeof (struct _IO_FILE_complete));
     }