gdb/python/py-prettyprint.c

   1 /* Python pretty-printing
   2
   3    Copyright (C) 2008-2022 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 "cli/cli-style.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 gdbpy_ref<>
  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;
  82     }
  83
  84   return gdbpy_ref<>::new_reference (Py_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   for (objfile *obj : current_program_space->objfiles ())
  97     {
  98       gdbpy_ref<> objf = objfile_to_objfile_object (obj);
  99       if (objf == NULL)
 100         {
 101           /* Ignore the error and continue.  */
 102           PyErr_Clear ();
 103           continue;
 104         }
 105
 106       gdbpy_ref<> pp_list (objfpy_get_printers (objf.get (), NULL));
 107       gdbpy_ref<> function (search_pp_list (pp_list.get (), value));
 108
 109       /* If there is an error in any objfile list, abort the search and exit.  */
 110       if (function == NULL)
 111         return NULL;
 112
 113       if (function != Py_None)
 114         return function.release ();
 115     }
 116
 117   Py_RETURN_NONE;
 118 }
 119
 120 /* Subroutine of find_pretty_printer to simplify it.
 121    Look for a pretty-printer to print VALUE in the current program space.
 122    The result is NULL if there's an error and the search should be terminated.
 123    The result is Py_None, suitably inc-ref'd, if no pretty-printer was found.
 124    Otherwise the result is the pretty-printer function, suitably inc-ref'd.  */
 125
 126 static gdbpy_ref<>
 127 find_pretty_printer_from_progspace (PyObject *value)
 128 {
 129   gdbpy_ref<> obj = pspace_to_pspace_object (current_program_space);
 130
 131   if (obj == NULL)
 132     return NULL;
 133   gdbpy_ref<> pp_list (pspy_get_printers (obj.get (), NULL));
 134   return search_pp_list (pp_list.get (), value);
 135 }
 136
 137 /* Subroutine of find_pretty_printer to simplify it.
 138    Look for a pretty-printer to print VALUE in the gdb module.
 139    The result is NULL if there's an error and the search should be terminated.
 140    The result is Py_None, suitably inc-ref'd, if no pretty-printer was found.
 141    Otherwise the result is the pretty-printer function, suitably inc-ref'd.  */
 142
 143 static gdbpy_ref<>
 144 find_pretty_printer_from_gdb (PyObject *value)
 145 {
 146   /* Fetch the global pretty printer list.  */
 147   if (gdb_python_module == NULL
 148       || ! PyObject_HasAttrString (gdb_python_module, "pretty_printers"))
 149     return gdbpy_ref<>::new_reference (Py_None);
 150   gdbpy_ref<> pp_list (PyObject_GetAttrString (gdb_python_module,
 151                                                "pretty_printers"));
 152   if (pp_list == NULL || ! PyList_Check (pp_list.get ()))
 153     return gdbpy_ref<>::new_reference (Py_None);
 154
 155   return search_pp_list (pp_list.get (), value);
 156 }
 157
 158 /* Find the pretty-printing constructor function for VALUE.  If no
 159    pretty-printer exists, return None.  If one exists, return a new
 160    reference.  On error, set the Python error and return NULL.  */
 161
 162 static gdbpy_ref<>
 163 find_pretty_printer (PyObject *value)
 164 {
 165   /* Look at the pretty-printer list for each objfile
 166      in the current program-space.  */
 167   gdbpy_ref<> function (find_pretty_printer_from_objfiles (value));
 168   if (function == NULL || function != Py_None)
 169     return function;
 170
 171   /* Look at the pretty-printer list for the current program-space.  */
 172   function = find_pretty_printer_from_progspace (value);
 173   if (function == NULL || function != Py_None)
 174     return function;
 175
 176   /* Look at the pretty-printer list in the gdb module.  */
 177   return find_pretty_printer_from_gdb (value);
 178 }
 179
 180 /* Pretty-print a single value, via the printer object PRINTER.
 181    If the function returns a string, a PyObject containing the string
 182    is returned.  If the function returns Py_NONE that means the pretty
 183    printer returned the Python None as a value.  Otherwise, if the
 184    function returns a value,  *OUT_VALUE is set to the value, and NULL
 185    is returned.  On error, *OUT_VALUE is set to NULL, NULL is
 186    returned, with a python exception set.  */
 187
 188 static gdbpy_ref<>
 189 pretty_print_one_value (PyObject *printer, struct value **out_value)
 190 {
 191   gdbpy_ref<> result;
 192
 193   *out_value = NULL;
 194   try
 195     {
 196       if (!PyObject_HasAttr (printer, gdbpy_to_string_cst))
 197         result = gdbpy_ref<>::new_reference (Py_None);
 198       else
 199         {
 200           result.reset (PyObject_CallMethodObjArgs (printer, gdbpy_to_string_cst,
 201                                                     NULL));
 202           if (result != NULL)
 203             {
 204               if (! gdbpy_is_string (result.get ())
 205                   && ! gdbpy_is_lazy_string (result.get ())
 206                   && result != Py_None)
 207                 {
 208                   *out_value = convert_value_from_python (result.get ());
 209                   if (PyErr_Occurred ())
 210                     *out_value = NULL;
 211                   result = NULL;
 212                 }
 213             }
 214         }
 215     }
 216   catch (const gdb_exception &except)
 217     {
 218     }
 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_styled (stream, metadata_style.style (),
 264                         _("<error reading variable>"));
 265       else
 266         fprintf_styled (stream, metadata_style.style (),
 267                         _("<error reading variable: %s>"), msg.get ());
 268     }
 269   else
 270     gdbpy_print_stack ();
 271 }
 272
 273 /* Helper for gdbpy_apply_val_pretty_printer which calls to_string and
 274    formats the result.  */
 275
 276 static enum string_repr_result
 277 print_string_repr (PyObject *printer, const char *hint,
 278                    struct ui_file *stream, int recurse,
 279                    const struct value_print_options *options,
 280                    const struct language_defn *language,
 281                    struct gdbarch *gdbarch)
 282 {
 283   struct value *replacement = NULL;
 284   enum string_repr_result result = string_repr_ok;
 285
 286   gdbpy_ref<> py_str = pretty_print_one_value (printer, &replacement);
 287   if (py_str != NULL)
 288     {
 289       if (py_str == Py_None)
 290         result = string_repr_none;
 291       else if (gdbpy_is_lazy_string (py_str.get ()))
 292         {
 293           CORE_ADDR addr;
 294           long length;
 295           struct type *type;
 296           gdb::unique_xmalloc_ptr<char> encoding;
 297           struct value_print_options local_opts = *options;
 298
 299           gdbpy_extract_lazy_string (py_str.get (), &addr, &type,
 300                                      &length, &encoding);
 301
 302           local_opts.addressprint = 0;
 303           val_print_string (type, encoding.get (), addr, (int) length,
 304                             stream, &local_opts);
 305         }
 306       else
 307         {
 308           gdbpy_ref<> string
 309             = python_string_to_target_python_string (py_str.get ());
 310           if (string != NULL)
 311             {
 312               char *output;
 313               long length;
 314               struct type *type;
 315
 316               output = PyBytes_AS_STRING (string.get ());
 317               length = PyBytes_GET_SIZE (string.get ());
 318               type = builtin_type (gdbarch)->builtin_char;
 319
 320               if (hint && !strcmp (hint, "string"))
 321                 language->printstr (stream, type, (gdb_byte *) output,
 322                                     length, NULL, 0, options);
 323               else
 324                 fputs_filtered (output, stream);
 325             }
 326           else
 327             {
 328               result = string_repr_error;
 329               print_stack_unless_memory_error (stream);
 330             }
 331         }
 332     }
 333   else if (replacement)
 334     {
 335       struct value_print_options opts = *options;
 336
 337       opts.addressprint = 0;
 338       common_val_print (replacement, stream, recurse, &opts, language);
 339     }
 340   else
 341     {
 342       result = string_repr_error;
 343       print_stack_unless_memory_error (stream);
 344     }
 345
 346   return result;
 347 }
 348
 349 /* Helper for gdbpy_apply_val_pretty_printer that formats children of the
 350    printer, if any exist.  If is_py_none is true, then nothing has
 351    been printed by to_string, and format output accordingly. */
 352 static void
 353 print_children (PyObject *printer, const char *hint,
 354                 struct ui_file *stream, int recurse,
 355                 const struct value_print_options *options,
 356                 const struct language_defn *language,
 357                 int is_py_none)
 358 {
 359   int is_map, is_array, done_flag, pretty;
 360   unsigned int i;
 361
 362   if (! PyObject_HasAttr (printer, gdbpy_children_cst))
 363     return;
 364
 365   /* If we are printing a map or an array, we want some special
 366      formatting.  */
 367   is_map = hint && ! strcmp (hint, "map");
 368   is_array = hint && ! strcmp (hint, "array");
 369
 370   gdbpy_ref<> children (PyObject_CallMethodObjArgs (printer, gdbpy_children_cst,
 371                                                     NULL));
 372   if (children == NULL)
 373     {
 374       print_stack_unless_memory_error (stream);
 375       return;
 376     }
 377
 378   gdbpy_ref<> iter (PyObject_GetIter (children.get ()));
 379   if (iter == NULL)
 380     {
 381       print_stack_unless_memory_error (stream);
 382       return;
 383     }
 384
 385   /* Use the prettyformat_arrays option if we are printing an array,
 386      and the pretty option otherwise.  */
 387   if (is_array)
 388     pretty = options->prettyformat_arrays;
 389   else
 390     {
 391       if (options->prettyformat == Val_prettyformat)
 392         pretty = 1;
 393       else
 394         pretty = options->prettyformat_structs;
 395     }
 396
 397   done_flag = 0;
 398   for (i = 0; i < options->print_max; ++i)
 399     {
 400       PyObject *py_v;
 401       const char *name;
 402
 403       gdbpy_ref<> item (PyIter_Next (iter.get ()));
 404       if (item == NULL)
 405         {
 406           if (PyErr_Occurred ())
 407             print_stack_unless_memory_error (stream);
 408           /* Set a flag so we can know whether we printed all the
 409              available elements.  */
 410           else
 411             done_flag = 1;
 412           break;
 413         }
 414
 415       if (! PyTuple_Check (item.get ()) || PyTuple_Size (item.get ()) != 2)
 416         {
 417           PyErr_SetString (PyExc_TypeError,
 418                            _("Result of children iterator not a tuple"
 419                              " of two elements."));
 420           gdbpy_print_stack ();
 421           continue;
 422         }
 423       if (! PyArg_ParseTuple (item.get (), "sO", &name, &py_v))
 424         {
 425           /* The user won't necessarily get a stack trace here, so provide
 426              more context.  */
 427           if (gdbpy_print_python_errors_p ())
 428             fprintf_unfiltered (gdb_stderr,
 429                                 _("Bad result from children iterator.\n"));
 430           gdbpy_print_stack ();
 431           continue;
 432         }
 433
 434       /* Print initial "=" to separate print_string_repr output and
 435          children.  For other elements, there are three cases:
 436          1. Maps.  Print a "," after each value element.
 437          2. Arrays.  Always print a ",".
 438          3. Other.  Always print a ",".  */
 439       if (i == 0)
 440         {
 441           if (!is_py_none)
 442             fputs_filtered (" = ", stream);
 443         }
 444       else if (! is_map || i % 2 == 0)
 445         fputs_filtered (pretty ? "," : ", ", stream);
 446
 447       /* Skip printing children if max_depth has been reached.  This check
 448          is performed after print_string_repr and the "=" separator so that
 449          these steps are not skipped if the variable is located within the
 450          permitted depth.  */
 451       if (val_print_check_max_depth (stream, recurse, options, language))
 452         return;
 453       else if (i == 0)
 454         /* Print initial "{" to bookend children.  */
 455         fputs_filtered ("{", stream);
 456
 457       /* In summary mode, we just want to print "= {...}" if there is
 458          a value.  */
 459       if (options->summary)
 460         {
 461           /* This increment tricks the post-loop logic to print what
 462              we want.  */
 463           ++i;
 464           /* Likewise.  */
 465           pretty = 0;
 466           break;
 467         }
 468
 469       if (! is_map || i % 2 == 0)
 470         {
 471           if (pretty)
 472             {
 473               fputs_filtered ("\n", stream);
 474               print_spaces_filtered (2 + 2 * recurse, stream);
 475             }
 476           else
 477             wrap_here (n_spaces (2 + 2 *recurse));
 478         }
 479
 480       if (is_map && i % 2 == 0)
 481         fputs_filtered ("[", stream);
 482       else if (is_array)
 483         {
 484           /* We print the index, not whatever the child method
 485              returned as the name.  */
 486           if (options->print_array_indexes)
 487             fprintf_filtered (stream, "[%d] = ", i);
 488         }
 489       else if (! is_map)
 490         {
 491           fputs_filtered (name, stream);
 492           fputs_filtered (" = ", stream);
 493         }
 494
 495       if (gdbpy_is_lazy_string (py_v))
 496         {
 497           CORE_ADDR addr;
 498           struct type *type;
 499           long length;
 500           gdb::unique_xmalloc_ptr<char> encoding;
 501           struct value_print_options local_opts = *options;
 502
 503           gdbpy_extract_lazy_string (py_v, &addr, &type, &length, &encoding);
 504
 505           local_opts.addressprint = 0;
 506           val_print_string (type, encoding.get (), addr, (int) length, stream,
 507                             &local_opts);
 508         }
 509       else if (gdbpy_is_string (py_v))
 510         {
 511           gdb::unique_xmalloc_ptr<char> output;
 512
 513           output = python_string_to_host_string (py_v);
 514           if (!output)
 515             gdbpy_print_stack ();
 516           else
 517             fputs_filtered (output.get (), stream);
 518         }
 519       else
 520         {
 521           struct value *value = convert_value_from_python (py_v);
 522
 523           if (value == NULL)
 524             {
 525               gdbpy_print_stack ();
 526               error (_("Error while executing Python code."));
 527             }
 528           else
 529             {
 530               /* When printing the key of a map we allow one additional
 531                  level of depth.  This means the key will print before the
 532                  value does.  */
 533               struct value_print_options opt = *options;
 534               if (is_map && i % 2 == 0
 535                   && opt.max_depth != -1
 536                   && opt.max_depth < INT_MAX)
 537                 ++opt.max_depth;
 538               common_val_print (value, stream, recurse + 1, &opt, language);
 539             }
 540         }
 541
 542       if (is_map && i % 2 == 0)
 543         fputs_filtered ("] = ", stream);
 544     }
 545
 546   if (i)
 547     {
 548       if (!done_flag)
 549         {
 550           if (pretty)
 551             {
 552               fputs_filtered ("\n", stream);
 553               print_spaces_filtered (2 + 2 * recurse, stream);
 554             }
 555           fputs_filtered ("...", stream);
 556         }
 557       if (pretty)
 558         {
 559           fputs_filtered ("\n", stream);
 560           print_spaces_filtered (2 * recurse, stream);
 561         }
 562       fputs_filtered ("}", stream);
 563     }
 564 }
 565
 566 enum ext_lang_rc
 567 gdbpy_apply_val_pretty_printer (const struct extension_language_defn *extlang,
 568                                 struct value *value,
 569                                 struct ui_file *stream, int recurse,
 570                                 const struct value_print_options *options,
 571                                 const struct language_defn *language)
 572 {
 573   struct type *type = value_type (value);
 574   struct gdbarch *gdbarch = type->arch ();
 575   enum string_repr_result print_result;
 576
 577   if (value_lazy (value))
 578     value_fetch_lazy (value);
 579
 580   /* No pretty-printer support for unavailable values.  */
 581   if (!value_bytes_available (value, 0, TYPE_LENGTH (type)))
 582     return EXT_LANG_RC_NOP;
 583
 584   if (!gdb_python_initialized)
 585     return EXT_LANG_RC_NOP;
 586
 587   gdbpy_enter enter_py (gdbarch, language);
 588
 589   gdbpy_ref<> val_obj (value_to_value_object_no_release (value));
 590   if (val_obj == NULL)
 591     {
 592       print_stack_unless_memory_error (stream);
 593       return EXT_LANG_RC_ERROR;
 594     }
 595
 596   /* Find the constructor.  */
 597   gdbpy_ref<> printer (find_pretty_printer (val_obj.get ()));
 598   if (printer == NULL)
 599     {
 600       print_stack_unless_memory_error (stream);
 601       return EXT_LANG_RC_ERROR;
 602     }
 603
 604   if (printer == Py_None)
 605     return EXT_LANG_RC_NOP;
 606
 607   /* If we are printing a map, we want some special formatting.  */
 608   gdb::unique_xmalloc_ptr<char> hint (gdbpy_get_display_hint (printer.get ()));
 609
 610   /* Print the section */
 611   print_result = print_string_repr (printer.get (), hint.get (), stream,
 612                                     recurse, options, language, gdbarch);
 613   if (print_result != string_repr_error)
 614     print_children (printer.get (), hint.get (), stream, recurse, options,
 615                     language, print_result == string_repr_none);
 616
 617   if (PyErr_Occurred ())
 618     print_stack_unless_memory_error (stream);
 619   return EXT_LANG_RC_OK;
 620 }
 621
 622
 623 /* Apply a pretty-printer for the varobj code.  PRINTER_OBJ is the
 624    print object.  It must have a 'to_string' method (but this is
 625    checked by varobj, not here) which takes no arguments and
 626    returns a string.  The printer will return a value and in the case
 627    of a Python string being returned, this function will return a
 628    PyObject containing the string.  For any other type, *REPLACEMENT is
 629    set to the replacement value and this function returns NULL.  On
 630    error, *REPLACEMENT is set to NULL and this function also returns
 631    NULL.  */
 632 gdbpy_ref<>
 633 apply_varobj_pretty_printer (PyObject *printer_obj,
 634                              struct value **replacement,
 635                              struct ui_file *stream)
 636 {
 637   *replacement = NULL;
 638   gdbpy_ref<> py_str = pretty_print_one_value (printer_obj, replacement);
 639
 640   if (*replacement == NULL && py_str == NULL)
 641     print_stack_unless_memory_error (stream);
 642
 643   return py_str;
 644 }
 645
 646 /* Find a pretty-printer object for the varobj module.  Returns a new
 647    reference to the object if successful; returns NULL if not.  VALUE
 648    is the value for which a printer tests to determine if it
 649    can pretty-print the value.  */
 650 gdbpy_ref<>
 651 gdbpy_get_varobj_pretty_printer (struct value *value)
 652 {
 653   try
 654     {
 655       value = value_copy (value);
 656     }
 657   catch (const gdb_exception &except)
 658     {
 659       GDB_PY_HANDLE_EXCEPTION (except);
 660     }
 661
 662   gdbpy_ref<> val_obj (value_to_value_object (value));
 663   if (val_obj == NULL)
 664     return NULL;
 665
 666   return find_pretty_printer (val_obj.get ());
 667 }
 668
 669 /* A Python function which wraps find_pretty_printer and instantiates
 670    the resulting class.  This accepts a Value argument and returns a
 671    pretty printer instance, or None.  This function is useful as an
 672    argument to the MI command -var-set-visualizer.  */
 673 PyObject *
 674 gdbpy_default_visualizer (PyObject *self, PyObject *args)
 675 {
 676   PyObject *val_obj;
 677   struct value *value;
 678
 679   if (! PyArg_ParseTuple (args, "O", &val_obj))
 680     return NULL;
 681   value = value_object_to_value (val_obj);
 682   if (! value)
 683     {
 684       PyErr_SetString (PyExc_TypeError,
 685                        _("Argument must be a gdb.Value."));
 686       return NULL;
 687     }
 688
 689   return find_pretty_printer (val_obj).release ();
 690 }