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 (except, RETURN_MASK_ALL)
 216     {
 217     }
 218   END_CATCH
 219
 220   return result;
 221 }
 222
 223 /* Return the display hint for the object printer, PRINTER.  Return
 224    NULL if there is no display_hint method, or if the method did not
 225    return a string.  On error, print stack trace and return NULL.  On
 226    success, return an xmalloc()d string.  */
 227 gdb::unique_xmalloc_ptr<char>
 228 gdbpy_get_display_hint (PyObject *printer)
 229 {
 230   gdb::unique_xmalloc_ptr<char> result;
 231
 232   if (! PyObject_HasAttr (printer, gdbpy_display_hint_cst))
 233     return NULL;
 234
 235   gdbpy_ref<> hint (PyObject_CallMethodObjArgs (printer, gdbpy_display_hint_cst,
 236                                                 NULL));
 237   if (hint != NULL)
 238     {
 239       if (gdbpy_is_string (hint.get ()))
 240         {
 241           result = python_string_to_host_string (hint.get ());
 242           if (result == NULL)
 243             gdbpy_print_stack ();
 244         }
 245     }
 246   else
 247     gdbpy_print_stack ();
 248
 249   return result;
 250 }
 251
 252 /* A wrapper for gdbpy_print_stack that ignores MemoryError.  */
 253
 254 static void
 255 print_stack_unless_memory_error (struct ui_file *stream)
 256 {
 257   if (PyErr_ExceptionMatches (gdbpy_gdb_memory_error))
 258     {
 259       gdbpy_err_fetch fetched_error;
 260       gdb::unique_xmalloc_ptr<char> msg = fetched_error.to_string ();
 261
 262       if (msg == NULL || *msg == '\0')
 263         fprintf_filtered (stream, _("<error reading variable>"));
 264       else
 265         fprintf_filtered (stream, _("<error reading variable: %s>"),
 266                           msg.get ());
 267     }
 268   else
 269     gdbpy_print_stack ();
 270 }
 271
 272 /* Helper for gdbpy_apply_val_pretty_printer which calls to_string and
 273    formats the result.  */
 274
 275 static enum string_repr_result
 276 print_string_repr (PyObject *printer, const char *hint,
 277                    struct ui_file *stream, int recurse,
 278                    const struct value_print_options *options,
 279                    const struct language_defn *language,
 280                    struct gdbarch *gdbarch)
 281 {
 282   struct value *replacement = NULL;
 283   enum string_repr_result result = string_repr_ok;
 284
 285   gdbpy_ref<> py_str = pretty_print_one_value (printer, &replacement);
 286   if (py_str != NULL)
 287     {
 288       if (py_str == Py_None)
 289         result = string_repr_none;
 290       else if (gdbpy_is_lazy_string (py_str.get ()))
 291         {
 292           CORE_ADDR addr;
 293           long length;
 294           struct type *type;
 295           gdb::unique_xmalloc_ptr<char> encoding;
 296           struct value_print_options local_opts = *options;
 297
 298           gdbpy_extract_lazy_string (py_str.get (), &addr, &type,
 299                                      &length, &encoding);
 300
 301           local_opts.addressprint = 0;
 302           val_print_string (type, encoding.get (), addr, (int) length,
 303                             stream, &local_opts);
 304         }
 305       else
 306         {
 307           gdbpy_ref<> string
 308             = python_string_to_target_python_string (py_str.get ());
 309           if (string != NULL)
 310             {
 311               char *output;
 312               long length;
 313               struct type *type;
 314
 315               output = PyBytes_AS_STRING (string.get ());
 316               length = PyBytes_GET_SIZE (string.get ());
 317               type = builtin_type (gdbarch)->builtin_char;
 318
 319               if (hint && !strcmp (hint, "string"))
 320                 LA_PRINT_STRING (stream, type, (gdb_byte *) output,
 321                                  length, NULL, 0, options);
 322               else
 323                 fputs_filtered (output, stream);
 324             }
 325           else
 326             {
 327               result = string_repr_error;
 328               print_stack_unless_memory_error (stream);
 329             }
 330         }
 331     }
 332   else if (replacement)
 333     {
 334       struct value_print_options opts = *options;
 335
 336       opts.addressprint = 0;
 337       common_val_print (replacement, stream, recurse, &opts, language);
 338     }
 339   else
 340     {
 341       result = string_repr_error;
 342       print_stack_unless_memory_error (stream);
 343     }
 344
 345   return result;
 346 }
 347
 348 /* Helper for gdbpy_apply_val_pretty_printer that formats children of the
 349    printer, if any exist.  If is_py_none is true, then nothing has
 350    been printed by to_string, and format output accordingly. */
 351 static void
 352 print_children (PyObject *printer, const char *hint,
 353                 struct ui_file *stream, int recurse,
 354                 const struct value_print_options *options,
 355                 const struct language_defn *language,
 356                 int is_py_none)
 357 {
 358   int is_map, is_array, done_flag, pretty;
 359   unsigned int i;
 360
 361   if (! PyObject_HasAttr (printer, gdbpy_children_cst))
 362     return;
 363
 364   /* If we are printing a map or an array, we want some special
 365      formatting.  */
 366   is_map = hint && ! strcmp (hint, "map");
 367   is_array = hint && ! strcmp (hint, "array");
 368
 369   gdbpy_ref<> children (PyObject_CallMethodObjArgs (printer, gdbpy_children_cst,
 370                                                     NULL));
 371   if (children == NULL)
 372     {
 373       print_stack_unless_memory_error (stream);
 374       return;
 375     }
 376
 377   gdbpy_ref<> iter (PyObject_GetIter (children.get ()));
 378   if (iter == NULL)
 379     {
 380       print_stack_unless_memory_error (stream);
 381       return;
 382     }
 383
 384   /* Use the prettyformat_arrays option if we are printing an array,
 385      and the pretty option otherwise.  */
 386   if (is_array)
 387     pretty = options->prettyformat_arrays;
 388   else
 389     {
 390       if (options->prettyformat == Val_prettyformat)
 391         pretty = 1;
 392       else
 393         pretty = options->prettyformat_structs;
 394     }
 395
 396   done_flag = 0;
 397   for (i = 0; i < options->print_max; ++i)
 398     {
 399       PyObject *py_v;
 400       const char *name;
 401
 402       gdbpy_ref<> item (PyIter_Next (iter.get ()));
 403       if (item == NULL)
 404         {
 405           if (PyErr_Occurred ())
 406             print_stack_unless_memory_error (stream);
 407           /* Set a flag so we can know whether we printed all the
 408              available elements.  */
 409           else
 410             done_flag = 1;
 411           break;
 412         }
 413
 414       if (! PyTuple_Check (item.get ()) || PyTuple_Size (item.get ()) != 2)
 415         {
 416           PyErr_SetString (PyExc_TypeError,
 417                            _("Result of children iterator not a tuple"
 418                              " of two elements."));
 419           gdbpy_print_stack ();
 420           continue;
 421         }
 422       if (! PyArg_ParseTuple (item.get (), "sO", &name, &py_v))
 423         {
 424           /* The user won't necessarily get a stack trace here, so provide
 425              more context.  */
 426           if (gdbpy_print_python_errors_p ())
 427             fprintf_unfiltered (gdb_stderr,
 428                                 _("Bad result from children iterator.\n"));
 429           gdbpy_print_stack ();
 430           continue;
 431         }
 432
 433       /* Print initial "{".  For other elements, there are three
 434          cases:
 435          1. Maps.  Print a "," after each value element.
 436          2. Arrays.  Always print a ",".
 437          3. Other.  Always print a ",".  */
 438       if (i == 0)
 439         {
 440          if (is_py_none)
 441            fputs_filtered ("{", stream);
 442          else
 443            fputs_filtered (" = {", stream);
 444        }
 445
 446       else if (! is_map || i % 2 == 0)
 447         fputs_filtered (pretty ? "," : ", ", stream);
 448
 449       /* In summary mode, we just want to print "= {...}" if there is
 450          a value.  */
 451       if (options->summary)
 452         {
 453           /* This increment tricks the post-loop logic to print what
 454              we want.  */
 455           ++i;
 456           /* Likewise.  */
 457           pretty = 0;
 458           break;
 459         }
 460
 461       if (! is_map || i % 2 == 0)
 462         {
 463           if (pretty)
 464             {
 465               fputs_filtered ("\n", stream);
 466               print_spaces_filtered (2 + 2 * recurse, stream);
 467             }
 468           else
 469             wrap_here (n_spaces (2 + 2 *recurse));
 470         }
 471
 472       if (is_map && i % 2 == 0)
 473         fputs_filtered ("[", stream);
 474       else if (is_array)
 475         {
 476           /* We print the index, not whatever the child method
 477              returned as the name.  */
 478           if (options->print_array_indexes)
 479             fprintf_filtered (stream, "[%d] = ", i);
 480         }
 481       else if (! is_map)
 482         {
 483           fputs_filtered (name, stream);
 484           fputs_filtered (" = ", stream);
 485         }
 486
 487       if (gdbpy_is_lazy_string (py_v))
 488         {
 489           CORE_ADDR addr;
 490           struct type *type;
 491           long length;
 492           gdb::unique_xmalloc_ptr<char> encoding;
 493           struct value_print_options local_opts = *options;
 494
 495           gdbpy_extract_lazy_string (py_v, &addr, &type, &length, &encoding);
 496
 497           local_opts.addressprint = 0;
 498           val_print_string (type, encoding.get (), addr, (int) length, stream,
 499                             &local_opts);
 500         }
 501       else if (gdbpy_is_string (py_v))
 502         {
 503           gdb::unique_xmalloc_ptr<char> output;
 504
 505           output = python_string_to_host_string (py_v);
 506           if (!output)
 507             gdbpy_print_stack ();
 508           else
 509             fputs_filtered (output.get (), stream);
 510         }
 511       else
 512         {
 513           struct value *value = convert_value_from_python (py_v);
 514
 515           if (value == NULL)
 516             {
 517               gdbpy_print_stack ();
 518               error (_("Error while executing Python code."));
 519             }
 520           else
 521             common_val_print (value, stream, recurse + 1, options, language);
 522         }
 523
 524       if (is_map && i % 2 == 0)
 525         fputs_filtered ("] = ", stream);
 526     }
 527
 528   if (i)
 529     {
 530       if (!done_flag)
 531         {
 532           if (pretty)
 533             {
 534               fputs_filtered ("\n", stream);
 535               print_spaces_filtered (2 + 2 * recurse, stream);
 536             }
 537           fputs_filtered ("...", stream);
 538         }
 539       if (pretty)
 540         {
 541           fputs_filtered ("\n", stream);
 542           print_spaces_filtered (2 * recurse, stream);
 543         }
 544       fputs_filtered ("}", stream);
 545     }
 546 }
 547
 548 enum ext_lang_rc
 549 gdbpy_apply_val_pretty_printer (const struct extension_language_defn *extlang,
 550                                 struct type *type,
 551                                 LONGEST embedded_offset, CORE_ADDR address,
 552                                 struct ui_file *stream, int recurse,
 553                                 struct value *val,
 554                                 const struct value_print_options *options,
 555                                 const struct language_defn *language)
 556 {
 557   struct gdbarch *gdbarch = get_type_arch (type);
 558   struct value *value;
 559   enum string_repr_result print_result;
 560
 561   if (value_lazy (val))
 562     value_fetch_lazy (val);
 563
 564   /* No pretty-printer support for unavailable values.  */
 565   if (!value_bytes_available (val, embedded_offset, TYPE_LENGTH (type)))
 566     return EXT_LANG_RC_NOP;
 567
 568   if (!gdb_python_initialized)
 569     return EXT_LANG_RC_NOP;
 570
 571   gdbpy_enter enter_py (gdbarch, language);
 572
 573   /* Instantiate the printer.  */
 574   value = value_from_component (val, type, embedded_offset);
 575
 576   gdbpy_ref<> val_obj (value_to_value_object (value));
 577   if (val_obj == NULL)
 578     {
 579       print_stack_unless_memory_error (stream);
 580       return EXT_LANG_RC_ERROR;
 581     }
 582
 583   /* Find the constructor.  */
 584   gdbpy_ref<> printer (find_pretty_printer (val_obj.get ()));
 585   if (printer == NULL)
 586     {
 587       print_stack_unless_memory_error (stream);
 588       return EXT_LANG_RC_ERROR;
 589     }
 590
 591   if (printer == Py_None)
 592     return EXT_LANG_RC_NOP;
 593
 594   /* If we are printing a map, we want some special formatting.  */
 595   gdb::unique_xmalloc_ptr<char> hint (gdbpy_get_display_hint (printer.get ()));
 596
 597   /* Print the section */
 598   print_result = print_string_repr (printer.get (), hint.get (), stream,
 599                                     recurse, options, language, gdbarch);
 600   if (print_result != string_repr_error)
 601     print_children (printer.get (), hint.get (), stream, recurse, options,
 602                     language, print_result == string_repr_none);
 603
 604   if (PyErr_Occurred ())
 605     print_stack_unless_memory_error (stream);
 606   return EXT_LANG_RC_OK;
 607 }
 608
 609
 610 /* Apply a pretty-printer for the varobj code.  PRINTER_OBJ is the
 611    print object.  It must have a 'to_string' method (but this is
 612    checked by varobj, not here) which takes no arguments and
 613    returns a string.  The printer will return a value and in the case
 614    of a Python string being returned, this function will return a
 615    PyObject containing the string.  For any other type, *REPLACEMENT is
 616    set to the replacement value and this function returns NULL.  On
 617    error, *REPLACEMENT is set to NULL and this function also returns
 618    NULL.  */
 619 gdbpy_ref<>
 620 apply_varobj_pretty_printer (PyObject *printer_obj,
 621                              struct value **replacement,
 622                              struct ui_file *stream)
 623 {
 624   *replacement = NULL;
 625   gdbpy_ref<> py_str = pretty_print_one_value (printer_obj, replacement);
 626
 627   if (*replacement == NULL && py_str == NULL)
 628     print_stack_unless_memory_error (stream);
 629
 630   return py_str;
 631 }
 632
 633 /* Find a pretty-printer object for the varobj module.  Returns a new
 634    reference to the object if successful; returns NULL if not.  VALUE
 635    is the value for which a printer tests to determine if it
 636    can pretty-print the value.  */
 637 gdbpy_ref<>
 638 gdbpy_get_varobj_pretty_printer (struct value *value)
 639 {
 640   TRY
 641     {
 642       value = value_copy (value);
 643     }
 644   CATCH (except, RETURN_MASK_ALL)
 645     {
 646       GDB_PY_HANDLE_EXCEPTION (except);
 647     }
 648   END_CATCH
 649
 650   gdbpy_ref<> val_obj (value_to_value_object (value));
 651   if (val_obj == NULL)
 652     return NULL;
 653
 654   return find_pretty_printer (val_obj.get ());
 655 }
 656
 657 /* A Python function which wraps find_pretty_printer and instantiates
 658    the resulting class.  This accepts a Value argument and returns a
 659    pretty printer instance, or None.  This function is useful as an
 660    argument to the MI command -var-set-visualizer.  */
 661 PyObject *
 662 gdbpy_default_visualizer (PyObject *self, PyObject *args)
 663 {
 664   PyObject *val_obj;
 665   struct value *value;
 666
 667   if (! PyArg_ParseTuple (args, "O", &val_obj))
 668     return NULL;
 669   value = value_object_to_value (val_obj);
 670   if (! value)
 671     {
 672       PyErr_SetString (PyExc_TypeError,
 673                        _("Argument must be a gdb.Value."));
 674       return NULL;
 675     }
 676
 677   return find_pretty_printer (val_obj).release ();
 678 }