gdb/compile/compile-c-support.c

   1 /* C/C++ language support for compilation.
   2
   3    Copyright (C) 2014-2024 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 "compile-internal.h"
  21 #include "compile-c.h"
  22 #include "compile-cplus.h"
  23 #include "compile.h"
  24 #include "c-lang.h"
  25 #include "macrotab.h"
  26 #include "macroscope.h"
  27 #include "regcache.h"
  28 #include "gdbsupport/function-view.h"
  29 #include "gdbsupport/gdb-dlfcn.h"
  30 #include "gdbsupport/preprocessor.h"
  31 #include "gdbarch.h"
  32
  33 /* See compile-internal.h.  */
  34
  35 const char *
  36 c_get_mode_for_size (int size)
  37 {
  38   const char *mode = NULL;
  39
  40   switch (size)
  41     {
  42     case 1:
  43       mode = "QI";
  44       break;
  45     case 2:
  46       mode = "HI";
  47       break;
  48     case 4:
  49       mode = "SI";
  50       break;
  51     case 8:
  52       mode = "DI";
  53       break;
  54     default:
  55       internal_error (_("Invalid GCC mode size %d."), size);
  56     }
  57
  58   return mode;
  59 }
  60
  61 /* See compile-internal.h.  */
  62
  63 std::string
  64 c_get_range_decl_name (const struct dynamic_prop *prop)
  65 {
  66   return string_printf ("__gdb_prop_%s", host_address_to_string (prop));
  67 }
  68
  69 \f
  70
  71 /* Load the plug-in library FE_LIBCC and return the initialization function
  72    FE_CONTEXT.  */
  73
  74 template <typename FUNCTYPE>
  75 FUNCTYPE *
  76 load_libcompile (const char *fe_libcc, const char *fe_context)
  77 {
  78   FUNCTYPE *func;
  79
  80   /* gdb_dlopen will call error () on an error, so no need to check
  81      value.  */
  82   gdb_dlhandle_up handle = gdb_dlopen (fe_libcc);
  83   func = (FUNCTYPE *) gdb_dlsym (handle, fe_context);
  84
  85   if (func == NULL)
  86     error (_("could not find symbol %s in library %s"), fe_context, fe_libcc);
  87
  88   /* Leave the library open.  */
  89   handle.release ();
  90   return func;
  91 }
  92
  93 /* Return the compile instance associated with the current context.
  94    This function calls the symbol returned from the load_libcompile
  95    function.  FE_LIBCC is the library to load.  BASE_VERSION is the
  96    base compile plug-in version we support.  API_VERSION is the
  97    API version supported.  */
  98
  99 template <typename INSTTYPE, typename FUNCTYPE, typename CTXTYPE,
 100           typename BASE_VERSION_TYPE, typename API_VERSION_TYPE>
 101 std::unique_ptr<compile_instance>
 102 get_compile_context (const char *fe_libcc, const char *fe_context,
 103                      BASE_VERSION_TYPE base_version,
 104                      API_VERSION_TYPE api_version)
 105 {
 106   static FUNCTYPE *func;
 107   static CTXTYPE *context;
 108
 109   if (func == NULL)
 110     {
 111       func = load_libcompile<FUNCTYPE> (fe_libcc, fe_context);
 112       gdb_assert (func != NULL);
 113     }
 114
 115   context = (*func) (base_version, api_version);
 116   if (context == NULL)
 117     error (_("The loaded version of GCC does not support the required version "
 118              "of the API."));
 119
 120   return std::make_unique<INSTTYPE> (context);
 121 }
 122
 123 /* A C-language implementation of get_compile_context.  */
 124
 125 std::unique_ptr<compile_instance>
 126 c_get_compile_context ()
 127 {
 128   return get_compile_context
 129     <compile_c_instance, gcc_c_fe_context_function, gcc_c_context,
 130     gcc_base_api_version, gcc_c_api_version>
 131     (STRINGIFY (GCC_C_FE_LIBCC), STRINGIFY (GCC_C_FE_CONTEXT),
 132      GCC_FE_VERSION_0, GCC_C_FE_VERSION_0);
 133 }
 134
 135 /* A C++-language implementation of get_compile_context.  */
 136
 137 std::unique_ptr<compile_instance>
 138 cplus_get_compile_context ()
 139 {
 140   return get_compile_context
 141     <compile_cplus_instance, gcc_cp_fe_context_function, gcc_cp_context,
 142      gcc_base_api_version, gcc_cp_api_version>
 143     (STRINGIFY (GCC_CP_FE_LIBCC), STRINGIFY (GCC_CP_FE_CONTEXT),
 144      GCC_FE_VERSION_0, GCC_CP_FE_VERSION_0);
 145 }
 146
 147 \f
 148
 149 /* Write one macro definition.  */
 150
 151 static void
 152 print_one_macro (const char *name, const struct macro_definition *macro,
 153                  struct macro_source_file *source, int line,
 154                  ui_file *file)
 155 {
 156   /* Don't print command-line defines.  They will be supplied another
 157      way.  */
 158   if (line == 0)
 159     return;
 160
 161   /* None of -Wno-builtin-macro-redefined, #undef first
 162      or plain #define of the same value would avoid a warning.  */
 163   gdb_printf (file, "#ifndef %s\n# define %s", name, name);
 164
 165   if (macro->kind == macro_function_like)
 166     {
 167       int i;
 168
 169       gdb_puts ("(", file);
 170       for (i = 0; i < macro->argc; i++)
 171         {
 172           gdb_puts (macro->argv[i], file);
 173           if (i + 1 < macro->argc)
 174             gdb_puts (", ", file);
 175         }
 176       gdb_puts (")", file);
 177     }
 178
 179   gdb_printf (file, " %s\n#endif\n", macro->replacement);
 180 }
 181
 182 /* Write macro definitions at PC to FILE.  */
 183
 184 static void
 185 write_macro_definitions (const struct block *block, CORE_ADDR pc,
 186                          struct ui_file *file)
 187 {
 188   gdb::unique_xmalloc_ptr<struct macro_scope> scope;
 189
 190   if (block != NULL)
 191     scope = sal_macro_scope (find_pc_line (pc, 0));
 192   else
 193     scope = default_macro_scope ();
 194   if (scope == NULL)
 195     scope = user_macro_scope ();
 196
 197   if (scope != NULL && scope->file != NULL && scope->file->table != NULL)
 198     {
 199       macro_for_each_in_scope (scope->file, scope->line,
 200                                [&] (const char *name,
 201                                     const macro_definition *macro,
 202                                     macro_source_file *source,
 203                                     int line)
 204         {
 205           print_one_macro (name, macro, source, line, file);
 206         });
 207     }
 208 }
 209
 210 /* Generate a structure holding all the registers used by the function
 211    we're generating.  */
 212
 213 static void
 214 generate_register_struct (struct ui_file *stream, struct gdbarch *gdbarch,
 215                           const std::vector<bool> &registers_used)
 216 {
 217   int i;
 218   int seen = 0;
 219
 220   gdb_puts ("struct " COMPILE_I_SIMPLE_REGISTER_STRUCT_TAG " {\n",
 221             stream);
 222
 223   if (!registers_used.empty ())
 224     for (i = 0; i < gdbarch_num_regs (gdbarch); ++i)
 225       {
 226         if (registers_used[i])
 227           {
 228             struct type *regtype = check_typedef (register_type (gdbarch, i));
 229             std::string regname = compile_register_name_mangled (gdbarch, i);
 230
 231             seen = 1;
 232
 233             /* You might think we could use type_print here.  However,
 234                target descriptions often use types with names like
 235                "int64_t", which may not be defined in the inferior
 236                (and in any case would not be looked up due to the
 237                #pragma business).  So, we take a much simpler
 238                approach: for pointer- or integer-typed registers, emit
 239                the field in the most direct way; and for other
 240                register types (typically flags or vectors), emit a
 241                maximally-aligned array of the correct size.  */
 242
 243             gdb_puts ("  ", stream);
 244             switch (regtype->code ())
 245               {
 246               case TYPE_CODE_PTR:
 247                 gdb_printf (stream, "__gdb_uintptr %s",
 248                             regname.c_str ());
 249                 break;
 250
 251               case TYPE_CODE_INT:
 252                 {
 253                   const char *mode
 254                     = c_get_mode_for_size (regtype->length ());
 255
 256                   if (mode != NULL)
 257                     {
 258                       if (regtype->is_unsigned ())
 259                         gdb_puts ("unsigned ", stream);
 260                       gdb_printf (stream,
 261                                   "int %s"
 262                                   " __attribute__ ((__mode__(__%s__)))",
 263                                   regname.c_str (),
 264                                   mode);
 265                       break;
 266                     }
 267                 }
 268
 269                 [[fallthrough]];
 270
 271               default:
 272                 gdb_printf (stream,
 273                             "  unsigned char %s[%s]"
 274                             " __attribute__((__aligned__("
 275                             "__BIGGEST_ALIGNMENT__)))",
 276                             regname.c_str (),
 277                             pulongest (regtype->length ()));
 278               }
 279             gdb_puts (";\n", stream);
 280           }
 281       }
 282
 283   if (!seen)
 284     gdb_puts ("  char " COMPILE_I_SIMPLE_REGISTER_DUMMY ";\n",
 285               stream);
 286
 287   gdb_puts ("};\n\n", stream);
 288 }
 289
 290 /* C-language policy to emit a push user expression pragma into BUF.  */
 291
 292 struct c_push_user_expression
 293 {
 294   void push_user_expression (struct ui_file *buf)
 295   {
 296     gdb_puts ("#pragma GCC user_expression\n", buf);
 297   }
 298 };
 299
 300 /* C-language policy to emit a pop user expression pragma into BUF.
 301    For C, this is a nop.  */
 302
 303 struct pop_user_expression_nop
 304 {
 305   void pop_user_expression (struct ui_file *buf)
 306   {
 307     /* Nothing to do.  */
 308   }
 309 };
 310
 311 /* C-language policy to construct a code header for a block of code.
 312    Takes a scope TYPE argument which selects the correct header to
 313    insert into BUF.  */
 314
 315 struct c_add_code_header
 316 {
 317   void add_code_header (enum compile_i_scope_types type, struct ui_file *buf)
 318   {
 319     switch (type)
 320       {
 321       case COMPILE_I_SIMPLE_SCOPE:
 322         gdb_puts ("void "
 323                   GCC_FE_WRAPPER_FUNCTION
 324                   " (struct "
 325                   COMPILE_I_SIMPLE_REGISTER_STRUCT_TAG
 326                   " *"
 327                   COMPILE_I_SIMPLE_REGISTER_ARG_NAME
 328                   ") {\n",
 329                   buf);
 330         break;
 331
 332       case COMPILE_I_PRINT_ADDRESS_SCOPE:
 333       case COMPILE_I_PRINT_VALUE_SCOPE:
 334         /* <string.h> is needed for a memcpy call below.  */
 335         gdb_puts ("#include <string.h>\n"
 336                   "void "
 337                   GCC_FE_WRAPPER_FUNCTION
 338                   " (struct "
 339                   COMPILE_I_SIMPLE_REGISTER_STRUCT_TAG
 340                   " *"
 341                   COMPILE_I_SIMPLE_REGISTER_ARG_NAME
 342                   ", "
 343                   COMPILE_I_PRINT_OUT_ARG_TYPE
 344                   " "
 345                   COMPILE_I_PRINT_OUT_ARG
 346                   ") {\n",
 347                   buf);
 348         break;
 349
 350       case COMPILE_I_RAW_SCOPE:
 351         break;
 352
 353       default:
 354         gdb_assert_not_reached ("Unknown compiler scope reached.");
 355       }
 356   }
 357 };
 358
 359 /* C-language policy to construct a code footer for a block of code.
 360    Takes a scope TYPE which selects the correct footer to insert into BUF.  */
 361
 362 struct c_add_code_footer
 363 {
 364   void add_code_footer (enum compile_i_scope_types type, struct ui_file *buf)
 365   {
 366     switch (type)
 367       {
 368       case COMPILE_I_SIMPLE_SCOPE:
 369       case COMPILE_I_PRINT_ADDRESS_SCOPE:
 370       case COMPILE_I_PRINT_VALUE_SCOPE:
 371         gdb_puts ("}\n", buf);
 372         break;
 373
 374       case COMPILE_I_RAW_SCOPE:
 375         break;
 376
 377       default:
 378         gdb_assert_not_reached ("Unknown compiler scope reached.");
 379       }
 380   }
 381 };
 382
 383 /* C-language policy to emit the user code snippet INPUT into BUF based on the
 384    scope TYPE.  */
 385
 386 struct c_add_input
 387 {
 388   void add_input (enum compile_i_scope_types type, const char *input,
 389                   struct ui_file *buf)
 390   {
 391     switch (type)
 392       {
 393       case COMPILE_I_PRINT_ADDRESS_SCOPE:
 394       case COMPILE_I_PRINT_VALUE_SCOPE:
 395         gdb_printf (buf,
 396                     "__auto_type " COMPILE_I_EXPR_VAL " = %s;\n"
 397                     "typeof (%s) *" COMPILE_I_EXPR_PTR_TYPE ";\n"
 398                     "memcpy (" COMPILE_I_PRINT_OUT_ARG ", %s"
 399                     COMPILE_I_EXPR_VAL ",\n"
 400                     "sizeof (*" COMPILE_I_EXPR_PTR_TYPE "));\n"
 401                     , input, input,
 402                     (type == COMPILE_I_PRINT_ADDRESS_SCOPE
 403                      ? "&" : ""));
 404         break;
 405
 406       default:
 407         gdb_puts (input, buf);
 408         break;
 409       }
 410     gdb_puts ("\n", buf);
 411   }
 412 };
 413
 414 /* C++-language policy to emit a push user expression pragma into
 415    BUF.  */
 416
 417 struct cplus_push_user_expression
 418 {
 419   void push_user_expression (struct ui_file *buf)
 420   {
 421     gdb_puts ("#pragma GCC push_user_expression\n", buf);
 422   }
 423 };
 424
 425 /* C++-language policy to emit a pop user expression pragma into BUF.  */
 426
 427 struct cplus_pop_user_expression
 428 {
 429   void pop_user_expression (struct ui_file *buf)
 430   {
 431     gdb_puts ("#pragma GCC pop_user_expression\n", buf);
 432   }
 433 };
 434
 435 /* C++-language policy to construct a code header for a block of code.
 436    Takes a scope TYPE argument which selects the correct header to
 437    insert into BUF.  */
 438
 439 struct cplus_add_code_header
 440 {
 441   void add_code_header (enum compile_i_scope_types type, struct ui_file *buf)
 442   {
 443   switch (type)
 444     {
 445     case COMPILE_I_SIMPLE_SCOPE:
 446       gdb_puts ("void "
 447                 GCC_FE_WRAPPER_FUNCTION
 448                 " (struct "
 449                 COMPILE_I_SIMPLE_REGISTER_STRUCT_TAG
 450                 " *"
 451                 COMPILE_I_SIMPLE_REGISTER_ARG_NAME
 452                 ") {\n",
 453                 buf);
 454       break;
 455
 456     case COMPILE_I_PRINT_ADDRESS_SCOPE:
 457     case COMPILE_I_PRINT_VALUE_SCOPE:
 458       gdb_puts (
 459                 "#include <cstring>\n"
 460                 "#include <bits/move.h>\n"
 461                 "void "
 462                 GCC_FE_WRAPPER_FUNCTION
 463                 " (struct "
 464                 COMPILE_I_SIMPLE_REGISTER_STRUCT_TAG
 465                 " *"
 466                 COMPILE_I_SIMPLE_REGISTER_ARG_NAME
 467                 ", "
 468                 COMPILE_I_PRINT_OUT_ARG_TYPE
 469                 " "
 470                 COMPILE_I_PRINT_OUT_ARG
 471                 ") {\n",
 472                 buf);
 473       break;
 474
 475     case COMPILE_I_RAW_SCOPE:
 476       break;
 477
 478     default:
 479       gdb_assert_not_reached ("Unknown compiler scope reached.");
 480     }
 481   }
 482 };
 483
 484 /* C++-language policy to emit the user code snippet INPUT into BUF based on
 485    the scope TYPE.  */
 486
 487 struct cplus_add_input
 488 {
 489   void add_input (enum compile_i_scope_types type, const char *input,
 490                   struct ui_file *buf)
 491   {
 492     switch (type)
 493       {
 494       case COMPILE_I_PRINT_VALUE_SCOPE:
 495       case COMPILE_I_PRINT_ADDRESS_SCOPE:
 496         gdb_printf
 497           (buf,
 498            /* "auto" strips ref- and cv- qualifiers, so we need to also strip
 499               those from COMPILE_I_EXPR_PTR_TYPE.  */
 500            "auto " COMPILE_I_EXPR_VAL " = %s;\n"
 501            "typedef "
 502              "std::add_pointer<std::remove_cv<decltype (%s)>::type>::type "
 503              " __gdb_expr_ptr;\n"
 504            "__gdb_expr_ptr " COMPILE_I_EXPR_PTR_TYPE ";\n"
 505            "std::memcpy (" COMPILE_I_PRINT_OUT_ARG ", %s ("
 506            COMPILE_I_EXPR_VAL "),\n"
 507            "\tsizeof (*" COMPILE_I_EXPR_PTR_TYPE "));\n"
 508            ,input, input,
 509            (type == COMPILE_I_PRINT_ADDRESS_SCOPE
 510             ? "__builtin_addressof" : ""));
 511         break;
 512
 513       default:
 514         gdb_puts (input, buf);
 515         break;
 516       }
 517     gdb_puts ("\n", buf);
 518   }
 519 };
 520
 521 /* A host class representing a compile program.
 522
 523    CompileInstanceType is the type of the compile_instance for the
 524    language.
 525
 526    PushUserExpressionPolicy and PopUserExpressionPolicy are used to
 527    push and pop user expression pragmas to the compile plug-in.
 528
 529    AddCodeHeaderPolicy and AddCodeFooterPolicy are used to add the appropriate
 530    code header and footer, respectively.
 531
 532    AddInputPolicy adds the actual user code.  */
 533
 534 template <class CompileInstanceType, class PushUserExpressionPolicy,
 535           class PopUserExpressionPolicy, class AddCodeHeaderPolicy,
 536           class AddCodeFooterPolicy, class AddInputPolicy>
 537 class compile_program
 538   : private PushUserExpressionPolicy, private PopUserExpressionPolicy,
 539     private AddCodeHeaderPolicy, private AddCodeFooterPolicy,
 540     private AddInputPolicy
 541 {
 542 public:
 543
 544   /* Construct a compile_program using the compiler instance INST
 545      using the architecture given by GDBARCH.  */
 546   compile_program (CompileInstanceType *inst, struct gdbarch *gdbarch)
 547     : m_instance (inst), m_arch (gdbarch)
 548   {
 549   }
 550
 551   /* Take the source code provided by the user with the 'compile'
 552      command and compute the additional wrapping, macro, variable and
 553      register operations needed.  INPUT is the source code derived from
 554      the 'compile' command, EXPR_BLOCK denotes the block relevant contextually
 555      to the inferior when the expression was created, and EXPR_PC
 556      indicates the value of $PC.
 557
 558      Returns the text of the program to compile.  */
 559   std::string compute (const char *input, const struct block *expr_block,
 560                        CORE_ADDR expr_pc)
 561   {
 562     string_file var_stream;
 563     string_file buf;
 564
 565     /* Do not generate local variable information for "raw"
 566        compilations.  In this case we aren't emitting our own function
 567        and the user's code may only refer to globals.  */
 568     if (m_instance->scope () != COMPILE_I_RAW_SCOPE)
 569       {
 570         /* Generate the code to compute variable locations, but do it
 571            before generating the function header, so we can define the
 572            register struct before the function body.  This requires a
 573            temporary stream.  */
 574         std::vector<bool> registers_used
 575           = generate_c_for_variable_locations (m_instance, &var_stream, m_arch,
 576                                                expr_block, expr_pc);
 577
 578         buf.puts ("typedef unsigned int"
 579                   " __attribute__ ((__mode__(__pointer__)))"
 580                   " __gdb_uintptr;\n");
 581         buf.puts ("typedef int"
 582                   " __attribute__ ((__mode__(__pointer__)))"
 583                   " __gdb_intptr;\n");
 584
 585         /* Iterate all log2 sizes in bytes supported by c_get_mode_for_size.  */
 586         for (int i = 0; i < 4; ++i)
 587           {
 588             const char *mode = c_get_mode_for_size (1 << i);
 589
 590             gdb_assert (mode != NULL);
 591             buf.printf ("typedef int"
 592                         " __attribute__ ((__mode__(__%s__)))"
 593                         " __gdb_int_%s;\n",
 594                         mode, mode);
 595           }
 596
 597         generate_register_struct (&buf, m_arch, registers_used);
 598       }
 599
 600     AddCodeHeaderPolicy::add_code_header (m_instance->scope (), &buf);
 601
 602     if (m_instance->scope () == COMPILE_I_SIMPLE_SCOPE
 603         || m_instance->scope () == COMPILE_I_PRINT_ADDRESS_SCOPE
 604         || m_instance->scope () == COMPILE_I_PRINT_VALUE_SCOPE)
 605       {
 606         buf.write (var_stream.c_str (), var_stream.size ());
 607         PushUserExpressionPolicy::push_user_expression (&buf);
 608       }
 609
 610     write_macro_definitions (expr_block, expr_pc, &buf);
 611
 612     /* The user expression has to be in its own scope, so that "extern"
 613        works properly.  Otherwise gcc thinks that the "extern"
 614        declaration is in the same scope as the declaration provided by
 615        gdb.  */
 616     if (m_instance->scope () != COMPILE_I_RAW_SCOPE)
 617       buf.puts ("{\n");
 618
 619     buf.puts ("#line 1 \"gdb command line\"\n");
 620
 621     AddInputPolicy::add_input (m_instance->scope (), input, &buf);
 622
 623     /* For larger user expressions the automatic semicolons may be
 624        confusing.  */
 625     if (strchr (input, '\n') == NULL)
 626       buf.puts (";\n");
 627
 628     if (m_instance->scope () != COMPILE_I_RAW_SCOPE)
 629       buf.puts ("}\n");
 630
 631     if (m_instance->scope () == COMPILE_I_SIMPLE_SCOPE
 632         || m_instance->scope () == COMPILE_I_PRINT_ADDRESS_SCOPE
 633         || m_instance->scope () == COMPILE_I_PRINT_VALUE_SCOPE)
 634       PopUserExpressionPolicy::pop_user_expression (&buf);
 635
 636     AddCodeFooterPolicy::add_code_footer (m_instance->scope (), &buf);
 637     return buf.release ();
 638   }
 639
 640 private:
 641
 642   /* The compile instance to be used for compilation and
 643      type-conversion.  */
 644   CompileInstanceType *m_instance;
 645
 646   /* The architecture to be used.  */
 647   struct gdbarch *m_arch;
 648 };
 649
 650 /* The types used for C and C++ program computations.  */
 651
 652 typedef compile_program<compile_c_instance,
 653                         c_push_user_expression, pop_user_expression_nop,
 654                         c_add_code_header, c_add_code_footer,
 655                         c_add_input> c_compile_program;
 656
 657 typedef compile_program<compile_cplus_instance,
 658                         cplus_push_user_expression, cplus_pop_user_expression,
 659                         cplus_add_code_header, c_add_code_footer,
 660                         cplus_add_input> cplus_compile_program;
 661
 662 /* The compute_program method for C.  */
 663
 664 std::string
 665 c_compute_program (compile_instance *inst,
 666                    const char *input,
 667                    struct gdbarch *gdbarch,
 668                    const struct block *expr_block,
 669                    CORE_ADDR expr_pc)
 670 {
 671   compile_c_instance *c_inst = static_cast<compile_c_instance *> (inst);
 672   c_compile_program program (c_inst, gdbarch);
 673
 674   return program.compute (input, expr_block, expr_pc);
 675 }
 676
 677 /* The compute_program method for C++.  */
 678
 679 std::string
 680 cplus_compute_program (compile_instance *inst,
 681                        const char *input,
 682                        struct gdbarch *gdbarch,
 683                        const struct block *expr_block,
 684                        CORE_ADDR expr_pc)
 685 {
 686   compile_cplus_instance *cplus_inst
 687     = static_cast<compile_cplus_instance *> (inst);
 688   cplus_compile_program program (cplus_inst, gdbarch);
 689
 690   return program.compute (input, expr_block, expr_pc);
 691 }