gdb/python/py-prettyprint.c

   1 /* Python pretty-printing
   2
   3    Copyright (C) 2008-2019 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
  29 /* Return type of print_string_repr.  */
  30
  31 enum string_repr_result
  32   {
  33     /* The string method returned None.  */
  34     string_repr_none,
  35     /* The string method had an error.  */
  36     string_repr_error,
  37     /* Everything ok.  */
  38     string_repr_ok
  39   };
  40
  41 /* Helper function for find_pretty_printer which iterates over a list,
  42    calls each function and inspects output.  This will return a
  43    printer object if one recognizes VALUE.  If no printer is found, it
  44    will return None.  On error, it will set the Python error and
  45    return NULL.  */
  46
  47 static gdbpy_ref<>
  48 search_pp_list (PyObject *list, PyObject *value)
  49 {
  50   Py_ssize_t pp_list_size, list_index;
  51
  52   pp_list_size = PyList_Size (list);
  53   for (list_index = 0; list_index < pp_list_size; list_index++)
  54     {
  55       PyObject *function = PyList_GetItem (list, list_index);
  56       if (! function)
  57         return NULL;
  58
  59       /* Skip if disabled.  */
  60       if (PyObject_HasAttr (function, gdbpy_enabled_cst))
  61         {
  62           gdbpy_ref<> attr (PyObject_GetAttr (function, gdbpy_enabled_cst));
  63           int cmp;
  64
  65           if (attr == NULL)
  66             return NULL;
  67           cmp = PyObject_IsTrue (attr.get ());
  68           if (cmp == -1)
  69             return NULL;
  70
  71           if (!cmp)
  72             continue;
  73         }
  74
  75       gdbpy_ref<> printer (PyObject_CallFunctionObjArgs (function, value,
  76                                                          NULL));
  77       if (printer == NULL)
  78         return NULL;
  79       else if (printer != Py_None)
  80         return printer;
  81     }
  82
  83   return gdbpy_ref<>::new_reference (Py_None);
  84 }
  85
  86 /* Subroutine of find_pretty_printer to simplify it.
  87    Look for a pretty-printer to print VALUE in all objfiles.
  88    The result is NULL if there's an error and the search should be terminated.
  89    The result is Py_None, suitably inc-ref'd, if no pretty-printer was found.
  90    Otherwise the result is the pretty-printer function, suitably inc-ref'd.  */
  91
  92 static PyObject *
  93 find_pretty_printer_from_objfiles (PyObject *value)
  94 {
  95   for (objfile *obj : current_program_space->objfiles ())
  96     {
  97       gdbpy_ref<> objf = objfile_to_objfile_object (obj);
  98       if (objf == NULL)
  99         {
 100           /* Ignore the error and continue.  */
 101           PyErr_Clear ();
 102           continue;
 103         }
 104
 105       gdbpy_ref<> pp_list (objfpy_get_printers (objf.get (), NULL));
 106       gdbpy_ref<> function (search_pp_list (pp_list.get (), value));
 107
 108       /* If there is an error in any objfile list, abort the search and exit.  */
 109       if (function == NULL)
 110         return NULL;
 111
 112       if (function != Py_None)
 113         return function.release ();
 114     }
 115
 116   Py_RETURN_NONE;
 117 }
 118
 119 /* Subroutine of find_pretty_printer to simplify it.
 120    Look for a pretty-printer to print VALUE in the current program space.
 121    The result is NULL if there's an error and the search should be terminated.
 122    The result is Py_None, suitably inc-ref'd, if no pretty-printer was found.
 123    Otherwise the result is the pretty-printer function, suitably inc-ref'd.  */
 124
 125 static gdbpy_ref<>
 126 find_pretty_printer_from_progspace (PyObject *value)
 127 {
 128   gdbpy_ref<> obj = pspace_to_pspace_object (current_program_space);
 129
 130   if (obj == NULL)
 131     return NULL;
 132   gdbpy_ref<> pp_list (pspy_get_printers (obj.get (), NULL));
 133   return search_pp_list (pp_list.get (), value);
 134 }
 135
 136 /* Subroutine of find_pretty_printer to simplify it.
 137    Look for a pretty-printer to print VALUE in the gdb module.
 138    The result is NULL if there's an error and the search should be terminated.
 139    The result is Py_None, suitably inc-ref'd, if no pretty-printer was found.
 140    Otherwise the result is the pretty-printer function, suitably inc-ref'd.  */
 141
 142 static gdbpy_ref<>
 143 find_pretty_printer_from_gdb (PyObject *value)
 144 {
 145   /* Fetch the global pretty printer list.  */
 146   if (gdb_python_module == NULL
 147       || ! PyObject_HasAttrString (gdb_python_module, "pretty_printers"))
 148     return gdbpy_ref<>::new_reference (Py_None);
 149   gdbpy_ref<> pp_list (PyObject_GetAttrString (gdb_python_module,
 150                                                "pretty_printers"));
 151   if (pp_list == NULL || ! PyList_Check (pp_list.get ()))
 152     return gdbpy_ref<>::new_reference (Py_None);
 153
 154   return search_pp_list (pp_list.get (), value);
 155 }
 156
 157 /* Find the pretty-printing constructor function for VALUE.  If no
 158    pretty-printer exists, return None.  If one exists, return a new
 159    reference.  On error, set the Python error and return NULL.  */
 160
 161 static gdbpy_ref<>
 162 find_pretty_printer (PyObject *value)
 163 {
 164   /* Look at the pretty-printer list for each objfile
 165      in the current program-space.  */
 166   gdbpy_ref<> function (find_pretty_printer_from_objfiles (value));
 167   if (function == NULL || function != Py_None)
 168     return function;
 169
 170   /* Look at the pretty-printer list for the current program-space.  */
 171   function = find_pretty_printer_from_progspace (value);
 172   if (function == NULL || function != Py_None)
 173     return function;
 174
 175   /* Look at the pretty-printer list in the gdb module.  */
 176   return find_pretty_printer_from_gdb (value);
 177 }
 178
 179 /* Pretty-print a single value, via the printer object PRINTER.
 180    If the function returns a string, a PyObject containing the string
 181    is returned.  If the function returns Py_NONE that means the pretty
 182    printer returned the Python None as a value.  Otherwise, if the
 183    function returns a value,  *OUT_VALUE is set to the value, and NULL
 184    is returned.  On error, *OUT_VALUE is set to NULL, NULL is
 185    returned, with a python exception set.  */
 186
 187 static gdbpy_ref<>
 188 pretty_print_one_value (PyObject *printer, struct value **out_value)
 189 {
 190   gdbpy_ref<> result;
 191
 192   *out_value = NULL;
 193   try
 194     {
 195       if (!PyObject_HasAttr (printer, gdbpy_to_string_cst))
 196         result = gdbpy_ref<>::new_reference (Py_None);
 197       else
 198         {
 199           result.reset (PyObject_CallMethodObjArgs (printer, gdbpy_to_string_cst,
 200                                                     NULL));
 201           if (result != NULL)
 202             {
 203               if (! gdbpy_is_string (result.get ())
 204                   && ! gdbpy_is_lazy_string (result.get ())
 205                   && result != Py_None)
 206                 {
 207                   *out_value = convert_value_from_python (result.get ());
 208                   if (PyErr_Occurred ())
 209                     *out_value = NULL;
 210                   result = NULL;
 211                 }
 212             }
 213         }
 214     }
 215   catch (const gdb_exception &except)
 216     {
 217     }
 218
 219   return result;
 220 }
 221
 222 /* Return the display hint for the object printer, PRINTER.  Return
 223    NULL if there is no display_hint method, or if the method did not
 224    return a string.  On error, print stack trace and return NULL.  On
 225    success, return an xmalloc()d string.  */
 226 gdb::unique_xmalloc_ptr<char>
 227 gdbpy_get_display_hint (PyObject *printer)
 228 {
 229   gdb::unique_xmalloc_ptr<char> result;
 230
 231   if (! PyObject_HasAttr (printer, gdbpy_display_hint_cst))
 232     return NULL;
 233
 234   gdbpy_ref<> hint (PyObject_CallMethodObjArgs (printer, gdbpy_display_hint_cst,
 235                                                 NULL));
 236   if (hint != NULL)
 237     {
 238       if (gdbpy_is_string (hint.get ()))
 239         {
 240           result = python_string_to_host_string (hint.get ());
 241           if (result == NULL)
 242             gdbpy_print_stack ();
 243         }
 244     }
 245   else
 246     gdbpy_print_stack ();
 247
 248   return result;
 249 }
 250
 251 /* A wrapper for gdbpy_print_stack that ignores MemoryError.  */
 252
 253 static void
 254 print_stack_unless_memory_error (struct ui_file *stream)
 255 {
 256   if (PyErr_ExceptionMatches (gdbpy_gdb_memory_error))
 257     {
 258       gdbpy_err_fetch fetched_error;
 259       gdb::unique_xmalloc_ptr<char> msg = fetched_error.to_string ();
 260
 261       if (msg == NULL || *msg == '\0')
 262         fprintf_filtered (stream, _("<error reading variable>"));
 263       else
 264         fprintf_filtered (stream, _("<error reading variable: %s>"),
 265                           msg.get ());
 266     }
 267   else
 268     gdbpy_print_stack ();
 269 }
 270
 271 /* Helper for gdbpy_apply_val_pretty_printer which calls to_string and
 272    formats the result.  */
 273
 274 static enum string_repr_result
 275 print_string_repr (PyObject *printer, const char *hint,
 276                    struct ui_file *stream, int recurse,
 277                    const struct value_print_options *options,
 278                    const struct language_defn *language,
 279                    struct gdbarch *gdbarch)
 280 {
 281   struct value *replacement = NULL;
 282   enum string_repr_result result = string_repr_ok;
 283
 284   gdbpy_ref<> py_str = pretty_print_one_value (printer, &replacement);
 285   if (py_str != NULL)
 286     {
 287       if (py_str == Py_None)
 288         result = string_repr_none;
 289       else if (gdbpy_is_lazy_string (py_str.get ()))
 290         {
 291           CORE_ADDR addr;
 292           long length;
 293           struct type *type;
 294           gdb::unique_xmalloc_ptr<char> encoding;
 295           struct value_print_options local_opts = *options;
 296
 297           gdbpy_extract_lazy_string (py_str.get (), &addr, &type,
 298                                      &length, &encoding);
 299
 300           local_opts.addressprint = 0;
 301           val_print_string (type, encoding.get (), addr, (int) length,
 302                             stream, &local_opts);
 303         }
 304       else
 305         {
 306           gdbpy_ref<> string
 307             = python_string_to_target_python_string (py_str.get ());
 308           if (string != NULL)
 309             {
 310               char *output;
 311               long length;
 312               struct type *type;
 313
 314               output = PyBytes_AS_STRING (string.get ());
 315               length = PyBytes_GET_SIZE (string.get ());
 316               type = builtin_type (gdbarch)->builtin_char;
 317
 318               if (hint && !strcmp (hint, "string"))
 319                 LA_PRINT_STRING (stream, type, (gdb_byte *) output,
 320                                  length, NULL, 0, options);
 321               else
 322                 fputs_filtered (output, stream);
 323             }
 324           else
 325             {
 326               result = string_repr_error;
 327               print_stack_unless_memory_error (stream);
 328             }
 329         }
 330     }
 331   else if (replacement)
 332     {
 333       struct value_print_options opts = *options;
 334
 335       opts.addressprint = 0;
 336       common_val_print (replacement, stream, recurse, &opts, language);
 337     }
 338   else
 339     {
 340       result = string_repr_error;
 341       print_stack_unless_memory_error (stream);
 342     }
 343
 344   return result;
 345 }
 346
 347 /* Helper for gdbpy_apply_val_pretty_printer that formats children of the
 348    printer, if any exist.  If is_py_none is true, then nothing has
 349    been printed by to_string, and format output accordingly. */
 350 static void
 351 print_children (PyObject *printer, const char *hint,
 352                 struct ui_file *stream, int recurse,
 353                 const struct value_print_options *options,
 354                 const struct language_defn *language,
 355                 int is_py_none)
 356 {
 357   int is_map, is_array, done_flag, pretty;
 358   unsigned int i;
 359
 360   if (! PyObject_HasAttr (printer, gdbpy_children_cst))
 361     return;
 362
 363   /* If we are printing a map or an array, we want some special
 364      formatting.  */
 365   is_map = hint && ! strcmp (hint, "map");
 366   is_array = hint && ! strcmp (hint, "array");
 367
 368   gdbpy_ref<> children (PyObject_CallMethodObjArgs (printer, gdbpy_children_cst,
 369                                                     NULL));
 370   if (children == NULL)
 371     {
 372       print_stack_unless_memory_error (stream);
 373       return;
 374     }
 375
 376   gdbpy_ref<> iter (PyObject_GetIter (children.get ()));
 377   if (iter == NULL)
 378     {
 379       print_stack_unless_memory_error (stream);
 380       return;
 381     }
 382
 383   /* Use the prettyformat_arrays option if we are printing an array,
 384      and the pretty option otherwise.  */
 385   if (is_array)
 386     pretty = options->prettyformat_arrays;
 387   else
 388     {
 389       if (options->prettyformat == Val_prettyformat)
 390         pretty = 1;
 391       else
 392         pretty = options->prettyformat_structs;
 393     }
 394
 395   done_flag = 0;
 396   for (i = 0; i < options->print_max; ++i)
 397     {
 398       PyObject *py_v;
 399       const char *name;
 400
 401       gdbpy_ref<> item (PyIter_Next (iter.get ()));
 402       if (item == NULL)
 403         {
 404           if (PyErr_Occurred ())
 405             print_stack_unless_memory_error (stream);
 406           /* Set a flag so we can know whether we printed all the
 407              available elements.  */
 408           else
 409             done_flag = 1;
 410           break;
 411         }
 412
 413       if (! PyTuple_Check (item.get ()) || PyTuple_Size (item.get ()) != 2)
 414         {
 415           PyErr_SetString (PyExc_TypeError,
 416                            _("Result of children iterator not a tuple"
 417                              " of two elements."));
 418           gdbpy_print_stack ();
 419           continue;
 420         }
 421       if (! PyArg_ParseTuple (item.get (), "sO", &name, &py_v))
 422         {
 423           /* The user won't necessarily get a stack trace here, so provide
 424              more context.  */
 425           if (gdbpy_print_python_errors_p ())
 426             fprintf_unfiltered (gdb_stderr,
 427                                 _("Bad result from children iterator.\n"));
 428           gdbpy_print_stack ();
 429           continue;
 430         }
 431
 432       /* Print initial "{".  For other elements, there are three
 433          cases:
 434          1. Maps.  Print a "," after each value element.
 435          2. Arrays.  Always print a ",".
 436          3. Other.  Always print a ",".  */
 437       if (i == 0)
 438         {
 439          if (is_py_none)
 440            fputs_filtered ("{", stream);
 441          else
 442            fputs_filtered (" = {", stream);
 443        }
 444
 445       else if (! is_map || i % 2 == 0)
 446         fputs_filtered (pretty ? "," : ", ", stream);
 447
 448       /* In summary mode, we just want to print "= {...}" if there is
 449          a value.  */
 450       if (options->summary)
 451         {
 452           /* This increment tricks the post-loop logic to print what
 453              we want.  */
 454           ++i;
 455           /* Likewise.  */
 456           pretty = 0;
 457           break;
 458         }
 459
 460       if (! is_map || i % 2 == 0)
 461         {
 462           if (pretty)
 463             {
 464               fputs_filtered ("\n", stream);
 465               print_spaces_filtered (2 + 2 * recurse, stream);
 466             }
 467           else
 468             wrap_here (n_spaces (2 + 2 *recurse));
 469         }
 470
 471       if (is_map && i % 2 == 0)
 472         fputs_filtered ("[", stream);
 473       else if (is_array)
 474         {
 475           /* We print the index, not whatever the child method
 476              returned as the name.  */
 477           if (options->print_array_indexes)
 478             fprintf_filtered (stream, "[%d] = ", i);
 479         }
 480       else if (! is_map)
 481         {
 482           fputs_filtered (name, stream);
 483           fputs_filtered (" = ", stream);
 484         }
 485
 486       if (gdbpy_is_lazy_string (py_v))
 487         {
 488           CORE_ADDR addr;
 489           struct type *type;
 490           long length;
 491           gdb::unique_xmalloc_ptr<char> encoding;
 492           struct value_print_options local_opts = *options;
 493
 494           gdbpy_extract_lazy_string (py_v, &addr, &type, &length, &encoding);
 495
 496           local_opts.addressprint = 0;
 497           val_print_string (type, encoding.get (), addr, (int) length, stream,
 498                             &local_opts);
 499         }
 500       else if (gdbpy_is_string (py_v))
 501         {
 502           gdb::unique_xmalloc_ptr<char> output;
 503
 504           output = python_string_to_host_string (py_v);
 505           if (!output)
 506             gdbpy_print_stack ();
 507           else
 508             fputs_filtered (output.get (), stream);
 509         }
 510       else
 511         {
 512           struct value *value = convert_value_from_python (py_v);
 513
 514           if (value == NULL)
 515             {
 516               gdbpy_print_stack ();
 517               error (_("Error while executing Python code."));
 518             }
 519           else
 520             {
 521               /* When printing the key of a map we allow one additional
 522                  level of depth.  This means the key will print before the
 523                  value does.  */
 524               struct value_print_options opt = *options;
 525               if (is_map && i % 2 == 0
 526                   && opt.max_depth != -1
 527                   && opt.max_depth < INT_MAX)
 528                 ++opt.max_depth;
 529               common_val_print (value, stream, recurse + 1, &opt, language);
 530             }
 531         }
 532
 533       if (is_map && i % 2 == 0)
 534         fputs_filtered ("] = ", stream);
 535     }
 536
 537   if (i)
 538     {
 539       if (!done_flag)
 540         {
 541           if (pretty)
 542             {
 543               fputs_filtered ("\n", stream);
 544               print_spaces_filtered (2 + 2 * recurse, stream);
 545             }
 546           fputs_filtered ("...", stream);
 547         }
 548       if (pretty)
 549         {
 550           fputs_filtered ("\n", stream);
 551           print_spaces_filtered (2 * recurse, stream);
 552         }
 553       fputs_filtered ("}", stream);
 554     }
 555 }
 556
 557 enum ext_lang_rc
 558 gdbpy_apply_val_pretty_printer (const struct extension_language_defn *extlang,
 559                                 struct type *type,
 560                                 LONGEST embedded_offset, CORE_ADDR address,
 561                                 struct ui_file *stream, int recurse,
 562                                 struct value *val,
 563                                 const struct value_print_options *options,
 564                                 const struct language_defn *language)
 565 {
 566   struct gdbarch *gdbarch = get_type_arch (type);
 567   struct value *value;
 568   enum string_repr_result print_result;
 569
 570   if (value_lazy (val))
 571     value_fetch_lazy (val);
 572
 573   /* No pretty-printer support for unavailable values.  */
 574   if (!value_bytes_available (val, embedded_offset, TYPE_LENGTH (type)))
 575     return EXT_LANG_RC_NOP;
 576
 577   if (!gdb_python_initialized)
 578     return EXT_LANG_RC_NOP;
 579
 580   gdbpy_enter enter_py (gdbarch, language);
 581
 582   /* Instantiate the printer.  */
 583   value = value_from_component (val, type, embedded_offset);
 584
 585   gdbpy_ref<> val_obj (value_to_value_object (value));
 586   if (val_obj == NULL)
 587     {
 588       print_stack_unless_memory_error (stream);
 589       return EXT_LANG_RC_ERROR;
 590     }
 591
 592   /* Find the constructor.  */
 593   gdbpy_ref<> printer (find_pretty_printer (val_obj.get ()));
 594   if (printer == NULL)
 595     {
 596       print_stack_unless_memory_error (stream);
 597       return EXT_LANG_RC_ERROR;
 598     }
 599
 600   if (printer == Py_None)
 601     return EXT_LANG_RC_NOP;
 602
 603   if (val_print_check_max_depth (stream, recurse, options, language))
 604     return EXT_LANG_RC_OK;
 605
 606   /* If we are printing a map, we want some special formatting.  */
 607   gdb::unique_xmalloc_ptr<char> hint (gdbpy_get_display_hint (printer.get ()));
 608
 609   /* Print the section */
 610   print_result = print_string_repr (printer.get (), hint.get (), stream,
 611                                     recurse, options, language, gdbarch);
 612   if (print_result != string_repr_error)
 613     print_children (printer.get (), hint.get (), stream, recurse, options,
 614                     language, print_result == string_repr_none);
 615
 616   if (PyErr_Occurred ())
 617     print_stack_unless_memory_error (stream);
 618   return EXT_LANG_RC_OK;
 619 }
 620
 621
 622 /* Apply a pretty-printer for the varobj code.  PRINTER_OBJ is the
 623    print object.  It must have a 'to_string' method (but this is
 624    checked by varobj, not here) which takes no arguments and
 625    returns a string.  The printer will return a value and in the case
 626    of a Python string being returned, this function will return a
 627    PyObject containing the string.  For any other type, *REPLACEMENT is
 628    set to the replacement value and this function returns NULL.  On
 629    error, *REPLACEMENT is set to NULL and this function also returns
 630    NULL.  */
 631 gdbpy_ref<>
 632 apply_varobj_pretty_printer (PyObject *printer_obj,
 633                              struct value **replacement,
 634                              struct ui_file *stream)
 635 {
 636   *replacement = NULL;
 637   gdbpy_ref<> py_str = pretty_print_one_value (printer_obj, replacement);
 638
 639   if (*replacement == NULL && py_str == NULL)
 640     print_stack_unless_memory_error (stream);
 641
 642   return py_str;
 643 }
 644
 645 /* Find a pretty-printer object for the varobj module.  Returns a new
 646    reference to the object if successful; returns NULL if not.  VALUE
 647    is the value for which a printer tests to determine if it
 648    can pretty-print the value.  */
 649 gdbpy_ref<>
 650 gdbpy_get_varobj_pretty_printer (struct value *value)
 651 {
 652   try
 653     {
 654       value = value_copy (value);
 655     }
 656   catch (const gdb_exception &except)
 657     {
 658       GDB_PY_HANDLE_EXCEPTION (except);
 659     }
 660
 661   gdbpy_ref<> val_obj (value_to_value_object (value));
 662   if (val_obj == NULL)
 663     return NULL;
 664
 665   return find_pretty_printer (val_obj.get ());
 666 }
 667
 668 /* A Python function which wraps find_pretty_printer and instantiates
 669    the resulting class.  This accepts a Value argument and returns a
 670    pretty printer instance, or None.  This function is useful as an
 671    argument to the MI command -var-set-visualizer.  */
 672 PyObject *
 673 gdbpy_default_visualizer (PyObject *self, PyObject *args)
 674 {
 675   PyObject *val_obj;
 676   struct value *value;
 677
 678   if (! PyArg_ParseTuple (args, "O", &val_obj))
 679     return NULL;
 680   value = value_object_to_value (val_obj);
 681   if (! value)
 682     {
 683       PyErr_SetString (PyExc_TypeError,
 684                        _("Argument must be a gdb.Value."));
 685       return NULL;
 686     }
 687
 688   return find_pretty_printer (val_obj).release ();
 689 }