gdb/python/py-gdb-readline.c

   1 /* Readline support for Python.
   2
   3    Copyright (C) 2012-2020 Free Software Foundation, Inc.
   4
   5    This file is part of GDB.
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  19
  20 #include "defs.h"
  21 #include "python-internal.h"
  22 #include "top.h"
  23 #include "cli/cli-utils.h"
  24
  25 /* Readline function suitable for PyOS_ReadlineFunctionPointer, which
  26    is used for Python's interactive parser and raw_input.  In both
  27    cases, sys_stdin and sys_stdout are always stdin and stdout
  28    respectively, as far as I can tell; they are ignored and
  29    command_line_input is used instead.  */
  30
  31 static char *
  32 gdbpy_readline_wrapper (FILE *sys_stdin, FILE *sys_stdout,
  33 #if PY_MAJOR_VERSION == 3 && PY_MINOR_VERSION >= 4
  34                         const char *prompt)
  35 #else
  36                         char *prompt)
  37 #endif
  38 {
  39   int n;
  40   const char *p = NULL;
  41   char *q;
  42
  43   try
  44     {
  45       p = command_line_input (prompt, "python");
  46     }
  47   /* Handle errors by raising Python exceptions.  */
  48   catch (const gdb_exception &except)
  49     {
  50       /* Detect user interrupt (Ctrl-C).  */
  51       if (except.reason == RETURN_QUIT)
  52         return NULL;
  53
  54       /* The thread state is nulled during gdbpy_readline_wrapper,
  55          with the original value saved in the following undocumented
  56          variable (see Python's Parser/myreadline.c and
  57          Modules/readline.c).  */
  58       PyEval_RestoreThread (_PyOS_ReadlineTState);
  59       gdbpy_convert_exception (except);
  60       PyEval_SaveThread ();
  61       return NULL;
  62     }
  63
  64   /* Detect EOF (Ctrl-D).  */
  65   if (p == NULL)
  66     {
  67       q = (char *) PyMem_RawMalloc (1);
  68       if (q != NULL)
  69         q[0] = '\0';
  70       return q;
  71     }
  72
  73   n = strlen (p);
  74
  75   /* Copy the line to Python and return.  */
  76   q = (char *) PyMem_RawMalloc (n + 2);
  77   if (q != NULL)
  78     {
  79       strcpy (q, p);
  80       q[n] = '\n';
  81       q[n + 1] = '\0';
  82     }
  83   return q;
  84 }
  85
  86 /* Initialize Python readline support.  */
  87
  88 void
  89 gdbpy_initialize_gdb_readline (void)
  90 {
  91   /* Python's readline module conflicts with GDB's use of readline
  92      since readline is not reentrant.  Ideally, a reentrant wrapper to
  93      GDB's readline should be implemented to replace Python's readline
  94      and prevent conflicts.  For now, this file implements a
  95      sys.meta_path finder that simply fails to import the readline
  96      module.  */
  97   if (PyRun_SimpleString ("\
  98 import sys\n\
  99 \n\
 100 class GdbRemoveReadlineFinder:\n\
 101   def find_module(self, fullname, path=None):\n\
 102     if fullname == 'readline' and path is None:\n\
 103       return self\n\
 104     return None\n\
 105 \n\
 106   def load_module(self, fullname):\n\
 107     raise ImportError('readline module disabled under GDB')\n\
 108 \n\
 109 sys.meta_path.append(GdbRemoveReadlineFinder())\n\
 110 ") == 0)
 111     PyOS_ReadlineFunctionPointer = gdbpy_readline_wrapper;
 112 }
 113