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.

10 files changed, 119 insertions, 25 deletions

diff --git a/ChangeLog b/ChangeLog
index 62d732e6e7..93201b76a2 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,16 @@
+2019-01-31  Paul Pluzhnikov  <ppluzhnikov@google.com>
+
+	[BZ #24051]
+	* libio/ioputs.c (_IO_puts): Use stdout instead of _IO_stdout.
+	* libio/fileops.c (_IO_new_file_underflow): Likewise
+	* libio/wfileops.c (_IO_wfile_underflow): Likewise
+	* libio/putchar.c (putchar): Likewise.
+	* libio/putchar_u.c (putchar_unlocked): Likewise.
+	* libio/putwchar.c (putchar): Likewise.
+	* libio/putwchar_u.c (putwchar_unlocked): Likewise.
+	* libio/tst-bz24051.c: New test.
+	* libio/Makefile (tests): Add tst-bz24051
+
 2019-01-31  Paul Eggert  <eggert@cs.ucla.edu>
 
 	regex: fix read overrun [BZ #24114]
diff --git a/libio/Makefile b/libio/Makefile
index 5bee83e55c..dbeba88fc0 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 43e33820e3..d2070a856e 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 04ae323c6d..319e551de5 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 665f46685a..a3f4200cdb 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 37d03ad364..1eebf0fc8f 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 8d6b6a4df0..1f5c4176f8 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 cfb46fc253..d943220031 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 0000000000..cf0dc8024e
--- /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 78f20486e5..0367643703 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);