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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.)
This commit is contained in:
Florian Weimer 2019-02-18 11:49:54 +01:00
parent 6c29942cbf
commit a5406364ac
11 changed files with 65 additions and 51 deletions
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21
ChangeLog
View File

@ -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):

7
libio/iofclose.c
View File

@ -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)
{
fp->_flags = 0;
free(fp);
}
_IO_deallocate_file (fp);
return status;
}

3
libio/iofwide.c
View File

@ -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)
&& (fp == _IO_stdin || fp == _IO_stdout || fp == _IO_stderr))
if (__glibc_unlikely (&_IO_stdin_used == NULL) && _IO_legacy_file (fp))
/* This is for a stream in the glibc 2.0 format. */
return -1;
#endif

2
libio/iolibio.h
View File

@ -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))

3
libio/libio.h
View File

@ -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;

30
libio/libioP.h
View File

@ -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 { \

5
libio/oldfileops.c
View File

@ -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)
|| (fp != (struct _IO_FILE_plus *) _IO_stdin
&& fp != (struct _IO_FILE_plus *) _IO_stdout
&& fp != (struct _IO_FILE_plus *) _IO_stderr))
if (&_IO_stdin_used != NULL || !_IO_legacy_file ((FILE *) fp))
/* The object is dynamically allocated and large enough. Initialize
the _mode element as well. */
((struct _IO_FILE_complete *) fp)->_mode = -1;

7
libio/oldiofclose.c
View File

@ -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)
{
fp->_flags = 0;
free(fp);
}
_IO_deallocate_file (fp);
return status;
}

18
libio/oldstdfiles.c
View File

@ -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));
}

9
libio/stdfiles.c
View File

@ -25,11 +25,10 @@
in files containing the exception. */
/* 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 definitions of _IO_2_1_stdin_, _IO_2_1_stdout_,
and _IO_2_1_stderr_, the default values of stdin, stdout, stderr.
See oldstdfiles.c for glibc 2.0 legacy definitions without wide
character support. */
#include "libioP.h"

11
libio/stdio.c
View File

@ -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);