gdb/testsuite/lib/read1.c

   1 /* This is part of GDB, the GNU debugger.
   2
   3    Copyright 2011-2020 Free Software Foundation, Inc.
   4
   5    This program is free software; you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation; either version 3 of the License, or
   8    (at your option) any later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  17 */
  18
  19 #define _GNU_SOURCE 1
  20 #include <dlfcn.h>
  21 #include <unistd.h>
  22 #include <fcntl.h>
  23 #include <stdlib.h>
  24
  25 /* Wrap 'read', forcing it to return only one byte at a time, if
  26    reading from the terminal.  */
  27
  28 ssize_t
  29 read (int fd, void *buf, size_t count)
  30 {
  31   static ssize_t (*read2) (int fd, void *buf, size_t count) = NULL;
  32   if (read2 == NULL)
  33     {
  34       /* Use setenv (v, "", 1) rather than unsetenv (v) to work around
  35          https://core.tcl-lang.org/tcl/tktview?name=67fd4f973a "incorrect
  36          results of 'info exists' when unset env var in one interp and check
  37          for existence from another interp".  */
  38       setenv ("LD_PRELOAD", "", 1);
  39       read2 = dlsym (RTLD_NEXT, "read");
  40     }
  41   if (count > 1 && isatty (fd) >= 1)
  42     count = 1;
  43   return read2 (fd, buf, count);
  44 }