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.)

ChangeLog

@@ -1,3 +1,24 @@
+2019-02-18  Florian Weimer  <fweimer@redhat.com>
+
+	* libio/libio.h (_IO_stdin, _IO_stdout, _IO_stderr): Remove
+	declaration.
+	* libio/stdio.c (AL, AL2, _IO_stdin, _IO_stdout, _IO_stderr):
+	Remove definitions.
+	* libio/stdfiles.c: Update comment.
+	* libio/oldstdfiles.c (_IO_check_libio): Update comment.  Do not
+	set _IO_stdin, _IO_stdout, _IO_stderr.
+	* libio/libioP.h (_IO_fake_stdiobuf): Remove unused declaration.
+	[SHLIB_COMPAT (libc, GLIBC_2_0, GLIBC_2_1)] (_IO_legacy_file): New
+	inline function.
+	(_IO_deallocate_file): New inline function.
+	* libio/iolibio.h (_IO_vprintf): Remove definition.
+	* libio/iofclose.c (_IO_new_fclose): Use _IO_deallocate_file.
+	* libio/oldiofclose.c (_IO_old_fclose): Likewise.
+	* libio/iofwide.c (_IO_fwide): Use __glibc_unlikely and
+	_IO_legacy_file.
+	* libio/oldfileops.c (_IO_old_file_init_internal): Remove
+	__builtin_expect.  Use _IO_legacy_file.
+
 2019-02-18  Stefan Liebler  <stli@linux.ibm.com>
 
 	* sysdeps/unix/sysv/linux/tst-clone3.c (do_test):

libio/iofclose.c

@@ -71,12 +71,7 @@ _IO_new_fclose (FILE *fp)
       if (_IO_have_backup (fp))
 	_IO_free_backup_area (fp);
     }
-  if (fp != _IO_stdin && fp != _IO_stdout && fp != _IO_stderr)
+  _IO_deallocate_file (fp);
-    {
-      fp->_flags = 0;
-      free(fp);
-    }
-
   return status;
 }
 

libio/iofwide.c

@@ -87,8 +87,7 @@ _IO_fwide (FILE *fp, int mode)
   mode = mode < 0 ? -1 : (mode == 0 ? 0 : 1);
 
 #if SHLIB_COMPAT (libc, GLIBC_2_0, GLIBC_2_1)
-  if (__builtin_expect (&_IO_stdin_used == NULL, 0)
+  if (__glibc_unlikely (&_IO_stdin_used == NULL) && _IO_legacy_file (fp))
-      && (fp == _IO_stdin || fp == _IO_stdout || fp == _IO_stderr))
     /* This is for a stream in the glibc 2.0 format.  */
     return -1;
 #endif

libio/iolibio.h

@@ -58,8 +58,6 @@ extern int _IO_vsscanf (const char *, const char *, __gnuc_va_list) __THROW;
    == _IO_pos_BAD ? EOF : 0)
 #define _IO_rewind(FILE) \
   (void) _IO_seekoff_unlocked (FILE, 0, 0, _IOS_INPUT|_IOS_OUTPUT)
-#define _IO_vprintf(FORMAT, ARGS) \
-  _IO_vfprintf (_IO_stdout, FORMAT, ARGS)
 #define _IO_freopen(FILENAME, MODE, FP) \
   (_IO_file_close_it (FP), \
    _IO_file_fopen (FP, FILENAME, MODE, 1))

libio/libio.h

@@ -185,9 +185,6 @@ struct _IO_FILE_plus;
 extern struct _IO_FILE_plus _IO_2_1_stdin_;
 extern struct _IO_FILE_plus _IO_2_1_stdout_;
 extern struct _IO_FILE_plus _IO_2_1_stderr_;
-extern FILE *_IO_stdin attribute_hidden;
-extern FILE *_IO_stdout attribute_hidden;
-extern FILE *_IO_stderr attribute_hidden;
 
 struct _IO_cookie_file;
 

libio/libioP.h

@@ -817,7 +817,35 @@ extern int _IO_vscanf (const char *, va_list) __THROW;
 # endif
 #endif
 
-extern struct _IO_fake_stdiobuf _IO_stdin_buf, _IO_stdout_buf, _IO_stderr_buf;
+#if SHLIB_COMPAT (libc, GLIBC_2_0, GLIBC_2_1)
+/* See oldstdfiles.c.  These are the old stream variables.  */
+extern struct _IO_FILE_plus _IO_stdin_;
+extern struct _IO_FILE_plus _IO_stdout_;
+extern struct _IO_FILE_plus _IO_stderr_;
+
+static inline bool
+_IO_legacy_file (FILE *fp)
+{
+  return fp == (FILE *) &_IO_stdin_ || fp == (FILE *) &_IO_stdout_
+    || fp == (FILE *) &_IO_stderr_;
+}
+#endif
+
+/* Deallocate a stream if it is heap-allocated.  Preallocated
+   stdin/stdout/stderr streams are not deallocated. */
+static inline void
+_IO_deallocate_file (FILE *fp)
+{
+  /* The current stream variables.  */
+  if (fp == (FILE *) &_IO_2_1_stdin_ || fp == (FILE *) &_IO_2_1_stdout_
+      || fp == (FILE *) &_IO_2_1_stderr_)
+    return;
+#if SHLIB_COMPAT (libc, GLIBC_2_0, GLIBC_2_1)
+  if (_IO_legacy_file (fp))
+    return;
+#endif
+  free (fp);
+}
 
 #ifdef IO_DEBUG
 # define CHECK_FILE(FILE, RET) do {			\

libio/oldfileops.c

@@ -109,10 +109,7 @@ _IO_old_file_init_internal (struct _IO_FILE_plus *fp)
 			     - (int) sizeof (struct _IO_FILE_complete));
   fp->file._fileno = -1;
 
-  if (__builtin_expect (&_IO_stdin_used != NULL, 1)
+  if (&_IO_stdin_used != NULL || !_IO_legacy_file ((FILE *) fp))
-      || (fp != (struct _IO_FILE_plus *) _IO_stdin
-	  && fp != (struct _IO_FILE_plus *) _IO_stdout
-	  && fp != (struct _IO_FILE_plus *) _IO_stderr))
     /* The object is dynamically allocated and large enough.  Initialize
        the _mode element as well.  */
     ((struct _IO_FILE_complete *) fp)->_mode = -1;

libio/oldiofclose.c

@@ -58,12 +58,7 @@ _IO_old_fclose (FILE *fp)
   _IO_FINISH (fp);
   if (_IO_have_backup (fp))
     _IO_free_backup_area (fp);
-  if (fp != _IO_stdin && fp != _IO_stdout && fp != _IO_stderr)
+  _IO_deallocate_file (fp);
-    {
-      fp->_flags = 0;
-      free(fp);
-    }
-
   return status;
 }
 

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
+/* This file provides legacy definitions of _IO_stdin_, _IO_stdout_,
-   for C code.  Compare stdstreams.cc.
+   and _IO_stderr_.  See stdfiles.c for the current definitions.  */
-   (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.) */
 
 #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_;
+      stdin = (FILE *) &_IO_stdin_;
-      _IO_stdout = stdout = (FILE *) &_IO_stdout_;
+      stdout = (FILE *) &_IO_stdout_;
-      _IO_stderr = stderr = (FILE *) &_IO_stderr_;
+      stderr = (FILE *) &_IO_stderr_;
       _IO_list_all = &_IO_stderr_;
-      _IO_stdin->_vtable_offset = _IO_stdout->_vtable_offset =
+      stdin->_vtable_offset = stdout->_vtable_offset
-	_IO_stderr->_vtable_offset = stdin->_vtable_offset =
+	= stderr->_vtable_offset =
-	stdout->_vtable_offset = stderr->_vtable_offset =
 	((int) sizeof (struct _IO_FILE)
 	 - (int) sizeof (struct _IO_FILE_complete));
     }

libio/stdfiles.c

@@ -25,11 +25,10 @@
    in files containing the exception.  */
 
 
-/* This file provides definitions of _IO_stdin, _IO_stdout, and _IO_stderr
+/* This file provides definitions of _IO_2_1_stdin_, _IO_2_1_stdout_,
-   for C code.  Compare stdstreams.cc.
+   and _IO_2_1_stderr_, the default values of stdin, stdout, stderr.
-   (The difference is that here the vtable field is set to 0,
+   See oldstdfiles.c for glibc 2.0 legacy definitions without wide
-   so the objects defined are not valid C++ objects.  On the other
+   character support.  */
-   hand, we don't need a C++ compiler to build this file.) */
 
 #include "libioP.h"
 

libio/stdio.c

@@ -33,14 +33,3 @@
 FILE *stdin = (FILE *) &_IO_2_1_stdin_;
 FILE *stdout = (FILE *) &_IO_2_1_stdout_;
 FILE *stderr = (FILE *) &_IO_2_1_stderr_;
-
-#undef _IO_stdin
-#undef _IO_stdout
-#undef _IO_stderr
-#define AL(name) AL2 (name, _IO_##name)
-#define AL2(name, al) \
-  extern __typeof (name) al __attribute__ ((alias (#name),                    \
-                                            visibility ("hidden")))
-AL(stdin);
-AL(stdout);
-AL(stderr);