libio: use stdout in puts and putchar, etc [BZ #24051].

GLIBC explicitly allows one to assign a new FILE pointer to stdout and
other standard streams.  printf and wprintf were honouring assignment to
stdout and using the new value, but puts, putchar, and wide char variants
did not.

The stdout part is fixed here.  The stdin part will be fixed in a followup.

9 files changed, 106 insertions, 25 deletions

diff --git a/libio/Makefile b/libio/Makefile
index 5bee83e..dbeba88 100644
--- a/libio/Makefile
+++ b/libio/Makefile
@@ -65,7 +65,7 @@ tests = tst_swprintf tst_wprintf tst_swscanf tst_wscanf tst_getwc tst_putwc   \
 	tst-setvbuf1 tst-popen1 tst-fgetwc bug-wsetpos tst-fseek \
 	tst-fwrite-error tst-ftell-partial-wide tst-ftell-active-handler \
 	tst-ftell-append tst-fputws tst-bz22415 tst-fgetc-after-eof \
-	tst-sprintf-ub tst-sprintf-chk-ub
+	tst-sprintf-ub tst-sprintf-chk-ub tst-bz24051
 
 tests-internal = tst-vtables tst-vtables-interposed tst-readline
 
diff --git a/libio/fileops.c b/libio/fileops.c
index 43e3382..d2070a8 100644
--- a/libio/fileops.c
+++ b/libio/fileops.c
@@ -501,13 +501,13 @@ _IO_new_file_underflow (FILE *fp)
 	 traditional Unix systems did this for stdout.  stderr better
 	 not be line buffered.  So we do just that here
 	 explicitly.  --drepper */
-      _IO_acquire_lock (_IO_stdout);
+      _IO_acquire_lock (stdout);
 
-      if ((_IO_stdout->_flags & (_IO_LINKED | _IO_NO_WRITES | _IO_LINE_BUF))
+      if ((stdout->_flags & (_IO_LINKED | _IO_NO_WRITES | _IO_LINE_BUF))
 	  == (_IO_LINKED | _IO_LINE_BUF))
-	_IO_OVERFLOW (_IO_stdout, EOF);
+	_IO_OVERFLOW (stdout, EOF);
 
-      _IO_release_lock (_IO_stdout);
+      _IO_release_lock (stdout);
     }
 
   _IO_switch_to_get_mode (fp);
diff --git a/libio/ioputs.c b/libio/ioputs.c
index 04ae323..319e551 100644
--- a/libio/ioputs.c
+++ b/libio/ioputs.c
@@ -33,15 +33,15 @@ _IO_puts (const char *str)
 {
   int result = EOF;
   size_t len = strlen (str);
-  _IO_acquire_lock (_IO_stdout);
+  _IO_acquire_lock (stdout);
 
-  if ((_IO_vtable_offset (_IO_stdout) != 0
-       || _IO_fwide (_IO_stdout, -1) == -1)
-      && _IO_sputn (_IO_stdout, str, len) == len
-      && _IO_putc_unlocked ('\n', _IO_stdout) != EOF)
+  if ((_IO_vtable_offset (stdout) != 0
+       || _IO_fwide (stdout, -1) == -1)
+      && _IO_sputn (stdout, str, len) == len
+      && _IO_putc_unlocked ('\n', stdout) != EOF)
     result = MIN (INT_MAX, len + 1);
 
-  _IO_release_lock (_IO_stdout);
+  _IO_release_lock (stdout);
   return result;
 }
 
diff --git a/libio/putchar.c b/libio/putchar.c
index 665f466..a3f4200 100644
--- a/libio/putchar.c
+++ b/libio/putchar.c
@@ -24,9 +24,9 @@ int
 putchar (int c)
 {
   int result;
-  _IO_acquire_lock (_IO_stdout);
-  result = _IO_putc_unlocked (c, _IO_stdout);
-  _IO_release_lock (_IO_stdout);
+  _IO_acquire_lock (stdout);
+  result = _IO_putc_unlocked (c, stdout);
+  _IO_release_lock (stdout);
   return result;
 }
 
diff --git a/libio/putchar_u.c b/libio/putchar_u.c
index 37d03ad..1eebf0f 100644
--- a/libio/putchar_u.c
+++ b/libio/putchar_u.c
@@ -23,6 +23,6 @@
 int
 putchar_unlocked (int c)
 {
-  CHECK_FILE (_IO_stdout, EOF);
-  return _IO_putc_unlocked (c, _IO_stdout);
+  CHECK_FILE (stdout, EOF);
+  return _IO_putc_unlocked (c, stdout);
 }
diff --git a/libio/putwchar.c b/libio/putwchar.c
index 8d6b6a4..1f5c417 100644
--- a/libio/putwchar.c
+++ b/libio/putwchar.c
@@ -22,8 +22,8 @@ wint_t
 putwchar (wchar_t wc)
 {
   wint_t result;
-  _IO_acquire_lock (_IO_stdout);
-  result = _IO_putwc_unlocked (wc, _IO_stdout);
-  _IO_release_lock (_IO_stdout);
+  _IO_acquire_lock (stdout);
+  result = _IO_putwc_unlocked (wc, stdout);
+  _IO_release_lock (stdout);
   return result;
 }
diff --git a/libio/putwchar_u.c b/libio/putwchar_u.c
index cfb46fc..d943220 100644
--- a/libio/putwchar_u.c
+++ b/libio/putwchar_u.c
@@ -21,6 +21,6 @@
 wint_t
 putwchar_unlocked (wchar_t wc)
 {
-  CHECK_FILE (_IO_stdout, WEOF);
-  return _IO_putwc_unlocked (wc, _IO_stdout);
+  CHECK_FILE (stdout, WEOF);
+  return _IO_putwc_unlocked (wc, stdout);
 }
diff --git a/libio/tst-bz24051.c b/libio/tst-bz24051.c
new file mode 100644
index 0000000..cf0dc80
--- /dev/null
+++ b/libio/tst-bz24051.c
@@ -0,0 +1,81 @@
+/* Test that assigning to stdout redirects puts, putchar, etc (BZ#24051)
+   Copyright (C) 2019 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+
+/* Prevent putchar -> _IO_putc inline expansion.  */
+#define __NO_INLINE__
+#pragma GCC optimize("O0")
+
+#include <stdio.h>
+#include <string.h>
+#include <wchar.h>
+
+#include <array_length.h>
+#include <support/check.h>
+#include <support/temp_file.h>
+#include <support/test-driver.h>
+
+#undef putchar
+#undef putwchar
+
+static int
+do_test_narrow (void)
+{
+  char buf[100];
+  int fd = create_temp_file ("tst-bz24051", NULL);
+  stdout = fdopen (fd, "w+");
+  TEST_VERIFY_EXIT (stdout != NULL);
+
+  printf ("ab%s", "cd");
+  putchar ('e');
+  putchar_unlocked ('f');
+  puts ("ghi");
+
+  rewind (stdout);
+  TEST_VERIFY_EXIT (fgets (buf, sizeof (buf), stdout) != NULL);
+  TEST_VERIFY (strcmp (buf, "abcdefghi\n") == 0);
+
+  return 0;
+}
+
+static int
+do_test_wide (void)
+{
+  wchar_t buf[100];
+  int fd = create_temp_file ("tst-bz24051w", NULL);
+  stdout = fdopen (fd, "w+");
+  TEST_VERIFY_EXIT (stdout != NULL);
+
+  wprintf (L"ab%ls", L"cd");
+  putwchar (L'e');
+  putwchar_unlocked (L'f');
+
+  rewind (stdout);
+  TEST_VERIFY_EXIT (fgetws (buf, array_length (buf), stdout) != NULL);
+  TEST_VERIFY (wcscmp (buf, L"abcdef") == 0);
+
+  return 0;
+}
+
+static int
+do_test (void)
+{
+  return do_test_narrow () + do_test_wide ();
+}
+
+#include <support/test-driver.c>
diff --git a/libio/wfileops.c b/libio/wfileops.c
index 78f2048..0367643 100644
--- a/libio/wfileops.c
+++ b/libio/wfileops.c
@@ -208,13 +208,13 @@ _IO_wfile_underflow (FILE *fp)
 	 traditional Unix systems did this for stdout.  stderr better
 	 not be line buffered.  So we do just that here
 	 explicitly.  --drepper */
-      _IO_acquire_lock (_IO_stdout);
+      _IO_acquire_lock (stdout);
 
-      if ((_IO_stdout->_flags & (_IO_LINKED | _IO_NO_WRITES | _IO_LINE_BUF))
+      if ((stdout->_flags & (_IO_LINKED | _IO_NO_WRITES | _IO_LINE_BUF))
 	  == (_IO_LINKED | _IO_LINE_BUF))
-	_IO_OVERFLOW (_IO_stdout, EOF);
+	_IO_OVERFLOW (stdout, EOF);
 
-      _IO_release_lock (_IO_stdout);
+      _IO_release_lock (stdout);
     }
 
   _IO_switch_to_get_mode (fp);