gdb/python/py-prettyprint.c

   1 /* Python pretty-printing
   2
   3    Copyright (C) 2008-2017 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 "objfiles.h"
  22 #include "symtab.h"
  23 #include "language.h"
  24 #include "valprint.h"
  25 #include "extension-priv.h"
  26 #include "python.h"
  27 #include "python-internal.h"
  28 #include "py-ref.h"
  29
  30 /* Return type of print_string_repr.  */
  31
  32 enum string_repr_result
  33   {
  34     /* The string method returned None.  */
  35     string_repr_none,
  36     /* The string method had an error.  */
  37     string_repr_error,
  38     /* Everything ok.  */
  39     string_repr_ok
  40   };
  41
  42 /* Helper function for find_pretty_printer which iterates over a list,
  43    calls each function and inspects output.  This will return a
  44    printer object if one recognizes VALUE.  If no printer is found, it
  45    will return None.  On error, it will set the Python error and
  46    return NULL.  */
  47
  48 static PyObject *
  49 search_pp_list (PyObject *list, PyObject *value)
  50 {
  51   Py_ssize_t pp_list_size, list_index;
  52
  53   pp_list_size = PyList_Size (list);
  54   for (list_index = 0; list_index < pp_list_size; list_index++)
  55     {
  56       PyObject *function = PyList_GetItem (list, list_index);
  57       if (! function)
  58         return NULL;
  59
  60       /* Skip if disabled.  */
  61       if (PyObject_HasAttr (function, gdbpy_enabled_cst))
  62         {
  63           gdbpy_ref<> attr (PyObject_GetAttr (function, gdbpy_enabled_cst));
  64           int cmp;
  65
  66           if (attr == NULL)
  67             return NULL;
  68           cmp = PyObject_IsTrue (attr.get ());
  69           if (cmp == -1)
  70             return NULL;
  71
  72           if (!cmp)
  73             continue;
  74         }
  75
  76       gdbpy_ref<> printer (PyObject_CallFunctionObjArgs (function, value,
  77                                                          NULL));
  78       if (printer == NULL)
  79         return NULL;
  80       else if (printer != Py_None)
  81         return printer.release ();
  82     }
  83
  84   Py_RETURN_NONE;
  85 }
  86
  87 /* Subroutine of find_pretty_printer to simplify it.
  88    Look for a pretty-printer to print VALUE in all objfiles.
  89    The result is NULL if there's an error and the search should be terminated.
  90    The result is Py_None, suitably inc-ref'd, if no pretty-printer was found.
  91    Otherwise the result is the pretty-printer function, suitably inc-ref'd.  */
  92
  93 static PyObject *
  94 find_pretty_printer_from_objfiles (PyObject *value)
  95 {
  96   struct objfile *obj;
  97
  98   ALL_OBJFILES (obj)
  99   {
 100     PyObject *objf = objfile_to_objfile_object (obj);
 101     if (!objf)
 102       {
 103         /* Ignore the error and continue.  */
 104         PyErr_Clear ();
 105         continue;
 106       }
 107
 108     gdbpy_ref<> pp_list (objfpy_get_printers (objf, NULL));
 109     gdbpy_ref<> function (search_pp_list (pp_list.get (), value));
 110
 111     /* If there is an error in any objfile list, abort the search and exit.  */
 112     if (function == NULL)
 113       return NULL;
 114
 115     if (function != Py_None)
 116       return function.release ();
 117   }
 118
 119   Py_RETURN_NONE;
 120 }
 121
 122 /* Subroutine of find_pretty_printer to simplify it.
 123    Look for a pretty-printer to print VALUE in the current program space.
 124    The result is NULL if there's an error and the search should be terminated.
 125    The result is Py_None, suitably inc-ref'd, if no pretty-printer was found.
 126    Otherwise the result is the pretty-printer function, suitably inc-ref'd.  */
 127
 128 static PyObject *
 129 find_pretty_printer_from_progspace (PyObject *value)
 130 {
 131   PyObject *obj = pspace_to_pspace_object (current_program_space);
 132
 133   if (!obj)
 134     return NULL;
 135   gdbpy_ref<> pp_list (pspy_get_printers (obj, NULL));
 136   return search_pp_list (pp_list.get (), value);
 137 }
 138
 139 /* Subroutine of find_pretty_printer to simplify it.
 140    Look for a pretty-printer to print VALUE in the gdb module.
 141    The result is NULL if there's an error and the search should be terminated.
 142    The result is Py_None, suitably inc-ref'd, if no pretty-printer was found.
 143    Otherwise the result is the pretty-printer function, suitably inc-ref'd.  */
 144
 145 static PyObject *
 146 find_pretty_printer_from_gdb (PyObject *value)
 147 {
 148   /* Fetch the global pretty printer list.  */
 149   if (gdb_python_module == NULL
 150       || ! PyObject_HasAttrString (gdb_python_module, "pretty_printers"))
 151     Py_RETURN_NONE;
 152   gdbpy_ref<> pp_list (PyObject_GetAttrString (gdb_python_module,
 153                                                "pretty_printers"));
 154   if (pp_list == NULL || ! PyList_Check (pp_list.get ()))
 155     Py_RETURN_NONE;
 156
 157   return search_pp_list (pp_list.get (), value);
 158 }
 159
 160 /* Find the pretty-printing constructor function for VALUE.  If no
 161    pretty-printer exists, return None.  If one exists, return a new
 162    reference.  On error, set the Python error and return NULL.  */
 163
 164 static PyObject *
 165 find_pretty_printer (PyObject *value)
 166 {
 167   /* Look at the pretty-printer list for each objfile
 168      in the current program-space.  */
 169   gdbpy_ref<> function (find_pretty_printer_from_objfiles (value));
 170   if (function == NULL || function != Py_None)
 171     return function.release ();
 172
 173   /* Look at the pretty-printer list for the current program-space.  */
 174   function.reset (find_pretty_printer_from_progspace (value));
 175   if (function == NULL || function != Py_None)
 176     return function.release ();
 177
 178   /* Look at the pretty-printer list in the gdb module.  */
 179   return find_pretty_printer_from_gdb (value);
 180 }
 181
 182 /* Pretty-print a single value, via the printer object PRINTER.
 183    If the function returns a string, a PyObject containing the string
 184    is returned.  If the function returns Py_NONE that means the pretty
 185    printer returned the Python None as a value.  Otherwise, if the
 186    function returns a value,  *OUT_VALUE is set to the value, and NULL
 187    is returned.  On error, *OUT_VALUE is set to NULL, NULL is
 188    returned, with a python exception set.  */
 189
 190 static PyObject *
 191 pretty_print_one_value (PyObject *printer, struct value **out_value)
 192 {
 193   PyObject *result = NULL;
 194
 195   *out_value = NULL;
 196   TRY
 197     {
 198       result = PyObject_CallMethodObjArgs (printer, gdbpy_to_string_cst, NULL);
 199       if (result)
 200         {
 201           if (! gdbpy_is_string (result) && ! gdbpy_is_lazy_string (result)
 202               && result != Py_None)
 203             {
 204               *out_value = convert_value_from_python (result);
 205               if (PyErr_Occurred ())
 206                 *out_value = NULL;
 207               Py_DECREF (result);
 208               result = NULL;
 209             }
 210         }
 211     }
 212   CATCH (except, RETURN_MASK_ALL)
 213     {
 214     }
 215   END_CATCH
 216
 217   return result;
 218 }
 219
 220 /* Return the display hint for the object printer, PRINTER.  Return
 221    NULL if there is no display_hint method, or if the method did not
 222    return a string.  On error, print stack trace and return NULL.  On
 223    success, return an xmalloc()d string.  */
 224 gdb::unique_xmalloc_ptr<char>
 225 gdbpy_get_display_hint (PyObject *printer)
 226 {
 227   gdb::unique_xmalloc_ptr<char> result;
 228
 229   if (! PyObject_HasAttr (printer, gdbpy_display_hint_cst))
 230     return NULL;
 231
 232   gdbpy_ref<> hint (PyObject_CallMethodObjArgs (printer, gdbpy_display_hint_cst,
 233                                                 NULL));
 234   if (hint != NULL)
 235     {
 236       if (gdbpy_is_string (hint.get ()))
 237         {
 238           result = python_string_to_host_string (hint.get ());
 239           if (result == NULL)
 240             gdbpy_print_stack ();
 241         }
 242     }
 243   else
 244     gdbpy_print_stack ();
 245
 246   return result;
 247 }
 248
 249 /* A wrapper for gdbpy_print_stack that ignores MemoryError.  */
 250
 251 static void
 252 print_stack_unless_memory_error (struct ui_file *stream)
 253 {
 254   if (PyErr_ExceptionMatches (gdbpy_gdb_memory_error))
 255     {
 256       PyObject *type, *value, *trace;
 257
 258       PyErr_Fetch (&type, &value, &trace);
 259
 260       gdbpy_ref<> type_ref (type);
 261       gdbpy_ref<> value_ref (value);
 262       gdbpy_ref<> trace_ref (trace);
 263
 264       gdb::unique_xmalloc_ptr<char>
 265         msg (gdbpy_exception_to_string (type, value));
 266
 267       if (msg == NULL || *msg == '\0')
 268         fprintf_filtered (stream, _("<error reading variable>"));
 269       else
 270         fprintf_filtered (stream, _("<error reading variable: %s>"),
 271                           msg.get ());
 272     }
 273   else
 274     gdbpy_print_stack ();
 275 }
 276
 277 /* Helper for gdbpy_apply_val_pretty_printer which calls to_string and
 278    formats the result.  */
 279
 280 static enum string_repr_result
 281 print_string_repr (PyObject *printer, const char *hint,
 282                    struct ui_file *stream, int recurse,
 283                    const struct value_print_options *options,
 284                    const struct language_defn *language,
 285                    struct gdbarch *gdbarch)
 286 {
 287   struct value *replacement = NULL;
 288   enum string_repr_result result = string_repr_ok;
 289
 290   gdbpy_ref<> py_str (pretty_print_one_value (printer, &replacement));
 291   if (py_str != NULL)
 292     {
 293       if (py_str == Py_None)
 294         result = string_repr_none;
 295       else if (gdbpy_is_lazy_string (py_str.get ()))
 296         {
 297           CORE_ADDR addr;
 298           long length;
 299           struct type *type;
 300           gdb::unique_xmalloc_ptr<char> encoding;
 301           struct value_print_options local_opts = *options;
 302
 303           gdbpy_extract_lazy_string (py_str.get (), &addr, &type,
 304                                      &length, &encoding);
 305
 306           local_opts.addressprint = 0;
 307           val_print_string (type, encoding.get (), addr, (int) length,
 308                             stream, &local_opts);
 309         }
 310       else
 311         {
 312           gdbpy_ref<> string
 313             (python_string_to_target_python_string (py_str.get ()));
 314           if (string != NULL)
 315             {
 316               char *output;
 317               long length;
 318               struct type *type;
 319
 320 #ifdef IS_PY3K
 321               output = PyBytes_AS_STRING (string.get ());
 322               length = PyBytes_GET_SIZE (string.get ());
 323 #else
 324               output = PyString_AsString (string.get ());
 325               length = PyString_Size (string.get ());
 326 #endif
 327               type = builtin_type (gdbarch)->builtin_char;
 328
 329               if (hint && !strcmp (hint, "string"))
 330                 LA_PRINT_STRING (stream, type, (gdb_byte *) output,
 331                                  length, NULL, 0, options);
 332               else
 333                 fputs_filtered (output, stream);
 334             }
 335           else
 336             {
 337               result = string_repr_error;
 338               print_stack_unless_memory_error (stream);
 339             }
 340         }
 341     }
 342   else if (replacement)
 343     {
 344       struct value_print_options opts = *options;
 345
 346       opts.addressprint = 0;
 347       common_val_print (replacement, stream, recurse, &opts, language);
 348     }
 349   else
 350     {
 351       result = string_repr_error;
 352       print_stack_unless_memory_error (stream);
 353     }
 354
 355   return result;
 356 }
 357
 358 #ifndef IS_PY3K
 359
 360 /* Create a dummy PyFrameObject, needed to work around
 361    a Python-2.4 bug with generators.  */
 362 class dummy_python_frame
 363 {
 364  public:
 365
 366   dummy_python_frame ();
 367
 368   ~dummy_python_frame ()
 369   {
 370     if (m_valid)
 371       m_tstate->frame = m_saved_frame;
 372   }
 373
 374   bool failed () const
 375   {
 376     return !m_valid;
 377   }
 378
 379  private:
 380
 381   bool m_valid;
 382   PyFrameObject *m_saved_frame;
 383   gdbpy_ref<> m_frame;
 384   PyThreadState *m_tstate;
 385 };
 386
 387 dummy_python_frame::dummy_python_frame ()
 388 : m_valid (false),
 389   m_saved_frame (NULL),
 390   m_tstate (NULL)
 391 {
 392   PyCodeObject *code;
 393   PyFrameObject *frame;
 394
 395   gdbpy_ref<> empty_string (PyString_FromString (""));
 396   if (empty_string == NULL)
 397     return;
 398
 399   gdbpy_ref<> null_tuple (PyTuple_New (0));
 400   if (null_tuple == NULL)
 401     return;
 402
 403   code = PyCode_New (0,                   /* argcount */
 404                      0,                   /* locals */
 405                      0,                   /* stacksize */
 406                      0,                   /* flags */
 407                      empty_string.get (), /* code */
 408                      null_tuple.get (),   /* consts */
 409                      null_tuple.get (),   /* names */
 410                      null_tuple.get (),   /* varnames */
 411 #if PYTHON_API_VERSION >= 1010
 412                      null_tuple.get (),   /* freevars */
 413                      null_tuple.get (),   /* cellvars */
 414 #endif
 415                      empty_string.get (), /* filename */
 416                      empty_string.get (), /* name */
 417                      1,                   /* firstlineno */
 418                      empty_string.get ()  /* lnotab */
 419                      );
 420   if (code == NULL)
 421     return;
 422   gdbpy_ref<> code_holder ((PyObject *) code);
 423
 424   gdbpy_ref<> globals (PyDict_New ());
 425   if (globals == NULL)
 426     return;
 427
 428   m_tstate = PyThreadState_GET ();
 429   frame = PyFrame_New (m_tstate, code, globals.get (), NULL);
 430   if (frame == NULL)
 431     return;
 432
 433   m_frame.reset ((PyObject *) frame);
 434   m_tstate->frame = frame;
 435   m_saved_frame = frame->f_back;
 436   m_valid = true;
 437 }
 438 #endif
 439
 440 /* Helper for gdbpy_apply_val_pretty_printer that formats children of the
 441    printer, if any exist.  If is_py_none is true, then nothing has
 442    been printed by to_string, and format output accordingly. */
 443 static void
 444 print_children (PyObject *printer, const char *hint,
 445                 struct ui_file *stream, int recurse,
 446                 const struct value_print_options *options,
 447                 const struct language_defn *language,
 448                 int is_py_none)
 449 {
 450   int is_map, is_array, done_flag, pretty;
 451   unsigned int i;
 452
 453   if (! PyObject_HasAttr (printer, gdbpy_children_cst))
 454     return;
 455
 456   /* If we are printing a map or an array, we want some special
 457      formatting.  */
 458   is_map = hint && ! strcmp (hint, "map");
 459   is_array = hint && ! strcmp (hint, "array");
 460
 461   gdbpy_ref<> children (PyObject_CallMethodObjArgs (printer, gdbpy_children_cst,
 462                                                     NULL));
 463   if (children == NULL)
 464     {
 465       print_stack_unless_memory_error (stream);
 466       return;
 467     }
 468
 469   gdbpy_ref<> iter (PyObject_GetIter (children.get ()));
 470   if (iter == NULL)
 471     {
 472       print_stack_unless_memory_error (stream);
 473       return;
 474     }
 475
 476   /* Use the prettyformat_arrays option if we are printing an array,
 477      and the pretty option otherwise.  */
 478   if (is_array)
 479     pretty = options->prettyformat_arrays;
 480   else
 481     {
 482       if (options->prettyformat == Val_prettyformat)
 483         pretty = 1;
 484       else
 485         pretty = options->prettyformat_structs;
 486     }
 487
 488   /* Manufacture a dummy Python frame to work around Python 2.4 bug,
 489      where it insists on having a non-NULL tstate->frame when
 490      a generator is called.  */
 491 #ifndef IS_PY3K
 492   dummy_python_frame frame;
 493   if (frame.failed ())
 494     {
 495       gdbpy_print_stack ();
 496       return;
 497     }
 498 #endif
 499
 500   done_flag = 0;
 501   for (i = 0; i < options->print_max; ++i)
 502     {
 503       PyObject *py_v;
 504       const char *name;
 505
 506       gdbpy_ref<> item (PyIter_Next (iter.get ()));
 507       if (item == NULL)
 508         {
 509           if (PyErr_Occurred ())
 510             print_stack_unless_memory_error (stream);
 511           /* Set a flag so we can know whether we printed all the
 512              available elements.  */
 513           else
 514             done_flag = 1;
 515           break;
 516         }
 517
 518       if (! PyTuple_Check (item.get ()) || PyTuple_Size (item.get ()) != 2)
 519         {
 520           PyErr_SetString (PyExc_TypeError,
 521                            _("Result of children iterator not a tuple"
 522                              " of two elements."));
 523           gdbpy_print_stack ();
 524           continue;
 525         }
 526       if (! PyArg_ParseTuple (item.get (), "sO", &name, &py_v))
 527         {
 528           /* The user won't necessarily get a stack trace here, so provide
 529              more context.  */
 530           if (gdbpy_print_python_errors_p ())
 531             fprintf_unfiltered (gdb_stderr,
 532                                 _("Bad result from children iterator.\n"));
 533           gdbpy_print_stack ();
 534           continue;
 535         }
 536
 537       /* Print initial "{".  For other elements, there are three
 538          cases:
 539          1. Maps.  Print a "," after each value element.
 540          2. Arrays.  Always print a ",".
 541          3. Other.  Always print a ",".  */
 542       if (i == 0)
 543         {
 544          if (is_py_none)
 545            fputs_filtered ("{", stream);
 546          else
 547            fputs_filtered (" = {", stream);
 548        }
 549
 550       else if (! is_map || i % 2 == 0)
 551         fputs_filtered (pretty ? "," : ", ", stream);
 552
 553       /* In summary mode, we just want to print "= {...}" if there is
 554          a value.  */
 555       if (options->summary)
 556         {
 557           /* This increment tricks the post-loop logic to print what
 558              we want.  */
 559           ++i;
 560           /* Likewise.  */
 561           pretty = 0;
 562           break;
 563         }
 564
 565       if (! is_map || i % 2 == 0)
 566         {
 567           if (pretty)
 568             {
 569               fputs_filtered ("\n", stream);
 570               print_spaces_filtered (2 + 2 * recurse, stream);
 571             }
 572           else
 573             wrap_here (n_spaces (2 + 2 *recurse));
 574         }
 575
 576       if (is_map && i % 2 == 0)
 577         fputs_filtered ("[", stream);
 578       else if (is_array)
 579         {
 580           /* We print the index, not whatever the child method
 581              returned as the name.  */
 582           if (options->print_array_indexes)
 583             fprintf_filtered (stream, "[%d] = ", i);
 584         }
 585       else if (! is_map)
 586         {
 587           fputs_filtered (name, stream);
 588           fputs_filtered (" = ", stream);
 589         }
 590
 591       if (gdbpy_is_lazy_string (py_v))
 592         {
 593           CORE_ADDR addr;
 594           struct type *type;
 595           long length;
 596           gdb::unique_xmalloc_ptr<char> encoding;
 597           struct value_print_options local_opts = *options;
 598
 599           gdbpy_extract_lazy_string (py_v, &addr, &type, &length, &encoding);
 600
 601           local_opts.addressprint = 0;
 602           val_print_string (type, encoding.get (), addr, (int) length, stream,
 603                             &local_opts);
 604         }
 605       else if (gdbpy_is_string (py_v))
 606         {
 607           gdb::unique_xmalloc_ptr<char> output;
 608
 609           output = python_string_to_host_string (py_v);
 610           if (!output)
 611             gdbpy_print_stack ();
 612           else
 613             fputs_filtered (output.get (), stream);
 614         }
 615       else
 616         {
 617           struct value *value = convert_value_from_python (py_v);
 618
 619           if (value == NULL)
 620             {
 621               gdbpy_print_stack ();
 622               error (_("Error while executing Python code."));
 623             }
 624           else
 625             common_val_print (value, stream, recurse + 1, options, language);
 626         }
 627
 628       if (is_map && i % 2 == 0)
 629         fputs_filtered ("] = ", stream);
 630     }
 631
 632   if (i)
 633     {
 634       if (!done_flag)
 635         {
 636           if (pretty)
 637             {
 638               fputs_filtered ("\n", stream);
 639               print_spaces_filtered (2 + 2 * recurse, stream);
 640             }
 641           fputs_filtered ("...", stream);
 642         }
 643       if (pretty)
 644         {
 645           fputs_filtered ("\n", stream);
 646           print_spaces_filtered (2 * recurse, stream);
 647         }
 648       fputs_filtered ("}", stream);
 649     }
 650 }
 651
 652 enum ext_lang_rc
 653 gdbpy_apply_val_pretty_printer (const struct extension_language_defn *extlang,
 654                                 struct type *type,
 655                                 LONGEST embedded_offset, CORE_ADDR address,
 656                                 struct ui_file *stream, int recurse,
 657                                 struct value *val,
 658                                 const struct value_print_options *options,
 659                                 const struct language_defn *language)
 660 {
 661   struct gdbarch *gdbarch = get_type_arch (type);
 662   struct value *value;
 663   enum string_repr_result print_result;
 664   const gdb_byte *valaddr = value_contents_for_printing (val);
 665
 666   /* No pretty-printer support for unavailable values.  */
 667   if (!value_bytes_available (val, embedded_offset, TYPE_LENGTH (type)))
 668     return EXT_LANG_RC_NOP;
 669
 670   if (!gdb_python_initialized)
 671     return EXT_LANG_RC_NOP;
 672
 673   gdbpy_enter enter_py (gdbarch, language);
 674
 675   /* Instantiate the printer.  */
 676   value = value_from_component (val, type, embedded_offset);
 677
 678   gdbpy_ref<> val_obj (value_to_value_object (value));
 679   if (val_obj == NULL)
 680     {
 681       print_stack_unless_memory_error (stream);
 682       return EXT_LANG_RC_ERROR;
 683     }
 684
 685   /* Find the constructor.  */
 686   gdbpy_ref<> printer (find_pretty_printer (val_obj.get ()));
 687   if (printer == NULL)
 688     {
 689       print_stack_unless_memory_error (stream);
 690       return EXT_LANG_RC_ERROR;
 691     }
 692
 693   if (printer == Py_None)
 694     return EXT_LANG_RC_NOP;
 695
 696   /* If we are printing a map, we want some special formatting.  */
 697   gdb::unique_xmalloc_ptr<char> hint (gdbpy_get_display_hint (printer.get ()));
 698
 699   /* Print the section */
 700   print_result = print_string_repr (printer.get (), hint.get (), stream,
 701                                     recurse, options, language, gdbarch);
 702   if (print_result != string_repr_error)
 703     print_children (printer.get (), hint.get (), stream, recurse, options,
 704                     language, print_result == string_repr_none);
 705
 706   if (PyErr_Occurred ())
 707     print_stack_unless_memory_error (stream);
 708   return EXT_LANG_RC_OK;
 709 }
 710
 711
 712 /* Apply a pretty-printer for the varobj code.  PRINTER_OBJ is the
 713    print object.  It must have a 'to_string' method (but this is
 714    checked by varobj, not here) which takes no arguments and
 715    returns a string.  The printer will return a value and in the case
 716    of a Python string being returned, this function will return a
 717    PyObject containing the string.  For any other type, *REPLACEMENT is
 718    set to the replacement value and this function returns NULL.  On
 719    error, *REPLACEMENT is set to NULL and this function also returns
 720    NULL.  */
 721 PyObject *
 722 apply_varobj_pretty_printer (PyObject *printer_obj,
 723                              struct value **replacement,
 724                              struct ui_file *stream)
 725 {
 726   PyObject *py_str = NULL;
 727
 728   *replacement = NULL;
 729   py_str = pretty_print_one_value (printer_obj, replacement);
 730
 731   if (*replacement == NULL && py_str == NULL)
 732     print_stack_unless_memory_error (stream);
 733
 734   return py_str;
 735 }
 736
 737 /* Find a pretty-printer object for the varobj module.  Returns a new
 738    reference to the object if successful; returns NULL if not.  VALUE
 739    is the value for which a printer tests to determine if it
 740    can pretty-print the value.  */
 741 PyObject *
 742 gdbpy_get_varobj_pretty_printer (struct value *value)
 743 {
 744   TRY
 745     {
 746       value = value_copy (value);
 747     }
 748   CATCH (except, RETURN_MASK_ALL)
 749     {
 750       GDB_PY_HANDLE_EXCEPTION (except);
 751     }
 752   END_CATCH
 753
 754   gdbpy_ref<> val_obj (value_to_value_object (value));
 755   if (val_obj == NULL)
 756     return NULL;
 757
 758   return find_pretty_printer (val_obj.get ());
 759 }
 760
 761 /* A Python function which wraps find_pretty_printer and instantiates
 762    the resulting class.  This accepts a Value argument and returns a
 763    pretty printer instance, or None.  This function is useful as an
 764    argument to the MI command -var-set-visualizer.  */
 765 PyObject *
 766 gdbpy_default_visualizer (PyObject *self, PyObject *args)
 767 {
 768   PyObject *val_obj;
 769   PyObject *cons;
 770   struct value *value;
 771
 772   if (! PyArg_ParseTuple (args, "O", &val_obj))
 773     return NULL;
 774   value = value_object_to_value (val_obj);
 775   if (! value)
 776     {
 777       PyErr_SetString (PyExc_TypeError,
 778                        _("Argument must be a gdb.Value."));
 779       return NULL;
 780     }
 781
 782   cons = find_pretty_printer (val_obj);
 783   return cons;
 784 }