gdbsupport/common-exceptions.h

   1 /* Exception (throw catch) mechanism, for GDB, the GNU debugger.
   2
   3    Copyright (C) 1986-2024 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 #ifndef COMMON_COMMON_EXCEPTIONS_H
  21 #define COMMON_COMMON_EXCEPTIONS_H
  22
  23 #include <setjmp.h>
  24 #include <new>
  25 #include <memory>
  26 #include <string>
  27 #include <functional>
  28
  29 #include "gdbsupport/underlying.h"
  30
  31 /* Reasons for calling throw_exceptions().  NOTE: all reason values
  32    must be different from zero.  enum value 0 is reserved for internal
  33    use as the return value from an initial setjmp().  */
  34
  35 enum return_reason
  36   {
  37     /* SIGTERM sent to GDB.  */
  38     RETURN_FORCED_QUIT = -3,
  39     /* User interrupt.  */
  40     RETURN_QUIT = -2,
  41     /* Any other error.  */
  42     RETURN_ERROR
  43   };
  44
  45 #define RETURN_MASK(reason)     (1 << (int)(-reason))
  46
  47 typedef enum
  48 {
  49   RETURN_MASK_FORCED_QUIT = RETURN_MASK (RETURN_FORCED_QUIT),
  50   RETURN_MASK_QUIT = RETURN_MASK (RETURN_QUIT),
  51   RETURN_MASK_ERROR = RETURN_MASK (RETURN_ERROR),
  52   RETURN_MASK_ALL = (RETURN_MASK_FORCED_QUIT | RETURN_MASK_QUIT | RETURN_MASK_ERROR)
  53 } return_mask;
  54
  55 /* Describe all exceptions.  */
  56
  57 enum errors {
  58   GDB_NO_ERROR,
  59
  60   /* Any generic error, the corresponding text is in
  61      exception.message.  */
  62   GENERIC_ERROR,
  63
  64   /* Something requested was not found.  */
  65   NOT_FOUND_ERROR,
  66
  67   /* Thread library lacks support necessary for finding thread local
  68      storage.  */
  69   TLS_NO_LIBRARY_SUPPORT_ERROR,
  70
  71   /* Load module not found while attempting to find thread local storage.  */
  72   TLS_LOAD_MODULE_NOT_FOUND_ERROR,
  73
  74   /* Thread local storage has not been allocated yet.  */
  75   TLS_NOT_ALLOCATED_YET_ERROR,
  76
  77   /* Something else went wrong while attempting to find thread local
  78      storage.  The ``struct gdb_exception'' message field provides
  79      more detail.  */
  80   TLS_GENERIC_ERROR,
  81
  82   /* Problem parsing an XML document.  */
  83   XML_PARSE_ERROR,
  84
  85   /* Error accessing memory.  */
  86   MEMORY_ERROR,
  87
  88   /* Value not available.  E.g., a register was not collected in a
  89      traceframe.  */
  90   NOT_AVAILABLE_ERROR,
  91
  92   /* Value was optimized out.  Note: if the value was a register, this
  93      means the register was not saved in the frame.  */
  94   OPTIMIZED_OUT_ERROR,
  95
  96   /* DW_OP_entry_value resolving failed.  */
  97   NO_ENTRY_VALUE_ERROR,
  98
  99   /* Target throwing an error has been closed.  Current command should be
 100      aborted as the inferior state is no longer valid.  */
 101   TARGET_CLOSE_ERROR,
 102
 103   /* An undefined command was executed.  */
 104   UNDEFINED_COMMAND_ERROR,
 105
 106   /* Requested feature, method, mechanism, etc. is not supported.  */
 107   NOT_SUPPORTED_ERROR,
 108
 109   /* The number of candidates generated during line completion has
 110      reached the user's specified limit.  This isn't an error, this exception
 111      is used to halt searching for more completions, but for consistency
 112      "_ERROR" is appended to the name.  */
 113   MAX_COMPLETIONS_REACHED_ERROR,
 114
 115   /* Add more errors here.  */
 116   NR_ERRORS
 117 };
 118
 119 struct gdb_exception
 120 {
 121   gdb_exception ()
 122     : reason ((enum return_reason) 0),
 123       error (GDB_NO_ERROR)
 124   {
 125   }
 126
 127   gdb_exception (enum return_reason r, enum errors e)
 128     : reason (r),
 129       error (e)
 130   {
 131   }
 132
 133   gdb_exception (enum return_reason r, enum errors e,
 134                  const char *fmt, va_list ap)
 135     ATTRIBUTE_PRINTF (4, 0)
 136     : reason (r),
 137       error (e),
 138       message (std::make_shared<std::string> (string_vprintf (fmt, ap)))
 139   {
 140   }
 141
 142   /* The move constructor exists so that we can mark it "noexcept",
 143      which is a good practice for any sort of exception object.  */
 144   explicit gdb_exception (gdb_exception &&other) noexcept = default;
 145
 146   /* The copy constructor exists so that we can mark it "noexcept",
 147      which is a good practice for any sort of exception object.  */
 148   gdb_exception (const gdb_exception &other) noexcept
 149     : reason (other.reason),
 150       error (other.error),
 151       message (other.message)
 152   {
 153   }
 154
 155   /* The assignment operator exists so that we can mark it "noexcept",
 156      which is a good practice for any sort of exception object.  */
 157   gdb_exception &operator= (const gdb_exception &other) noexcept
 158   {
 159     reason = other.reason;
 160     error = other.error;
 161     message = other.message;
 162     return *this;
 163   }
 164
 165   gdb_exception &operator= (gdb_exception &&other) noexcept = default;
 166
 167   /* Return the contents of the exception message, as a C string.  The
 168      string remains owned by the exception object.  */
 169   const char *what () const noexcept
 170   {
 171     return message->c_str ();
 172   }
 173
 174   /* Compare two exceptions.  */
 175   bool operator== (const gdb_exception &other) const
 176   {
 177     const char *msg1 = message == nullptr ? "" : what ();
 178     const char *msg2 = other.message == nullptr ? "" : other.what ();
 179
 180     return (reason == other.reason
 181             && error == other.error
 182             && strcmp (msg1, msg2) == 0);
 183   }
 184
 185   /* Compare two exceptions.  */
 186   bool operator!= (const gdb_exception &other) const
 187   {
 188     return !(*this == other);
 189   }
 190
 191   enum return_reason reason;
 192   enum errors error;
 193   std::shared_ptr<std::string> message;
 194 };
 195
 196 namespace std
 197 {
 198
 199 /* Specialization of std::hash for gdb_exception.  */
 200 template<>
 201 struct hash<gdb_exception>
 202 {
 203   size_t operator() (const gdb_exception &exc) const
 204   {
 205     size_t result = to_underlying (exc.reason) + to_underlying (exc.error);
 206     if (exc.message != nullptr)
 207       result += std::hash<std::string> {} (*exc.message);
 208     return result;
 209   }
 210 };
 211
 212 }
 213
 214 /* Functions to drive the sjlj-based exceptions state machine.  Though
 215    declared here by necessity, these functions should be considered
 216    internal to the exceptions subsystem and not used other than via
 217    the TRY/CATCH (or TRY_SJLJ/CATCH_SJLJ) macros defined below.  */
 218
 219 extern jmp_buf *exceptions_state_mc_init (void);
 220 extern int exceptions_state_mc_action_iter (void);
 221 extern int exceptions_state_mc_action_iter_1 (void);
 222 extern int exceptions_state_mc_catch (struct gdb_exception *, int);
 223
 224 /* Macro to wrap up standard try/catch behavior.
 225
 226    The double loop lets us correctly handle code "break"ing out of the
 227    try catch block.  (It works as the "break" only exits the inner
 228    "while" loop, the outer for loop detects this handling it
 229    correctly.)  Of course "return" and "goto" are not so lucky.
 230
 231    For instance:
 232
 233    *INDENT-OFF*
 234
 235    TRY_SJLJ
 236      {
 237      }
 238    CATCH_SJLJ (e, RETURN_MASK_ERROR)
 239      {
 240        switch (e.reason)
 241          {
 242            case RETURN_ERROR: ...
 243          }
 244      }
 245    END_CATCH_SJLJ
 246
 247    The SJLJ variants are needed in some cases where gdb exceptions
 248    need to cross third-party library code compiled without exceptions
 249    support (e.g., readline).  */
 250
 251 #define TRY_SJLJ \
 252      { \
 253        jmp_buf *buf = \
 254          exceptions_state_mc_init (); \
 255        setjmp (*buf); \
 256      } \
 257      while (exceptions_state_mc_action_iter ()) \
 258        while (exceptions_state_mc_action_iter_1 ())
 259
 260 #define CATCH_SJLJ(EXCEPTION, MASK)                             \
 261   {                                                     \
 262     struct gdb_exception EXCEPTION;                             \
 263     if (exceptions_state_mc_catch (&(EXCEPTION), MASK))
 264
 265 #define END_CATCH_SJLJ                          \
 266   }
 267
 268 /* The exception types client code may catch.  They're just shims
 269    around gdb_exception that add nothing but type info.  Which is used
 270    is selected depending on the MASK argument passed to CATCH.  */
 271
 272 struct gdb_exception_error : public gdb_exception
 273 {
 274   gdb_exception_error (enum errors e, const char *fmt, va_list ap)
 275     ATTRIBUTE_PRINTF (3, 0)
 276     : gdb_exception (RETURN_ERROR, e, fmt, ap)
 277   {
 278   }
 279
 280   explicit gdb_exception_error (gdb_exception &&ex) noexcept
 281     : gdb_exception (std::move (ex))
 282   {
 283     gdb_assert (ex.reason == RETURN_ERROR);
 284   }
 285 };
 286
 287 struct gdb_exception_quit : public gdb_exception
 288 {
 289   gdb_exception_quit (const char *fmt, va_list ap)
 290     ATTRIBUTE_PRINTF (2, 0)
 291     : gdb_exception (RETURN_QUIT, GDB_NO_ERROR, fmt, ap)
 292   {
 293   }
 294
 295   explicit gdb_exception_quit (gdb_exception &&ex) noexcept
 296     : gdb_exception (std::move (ex))
 297   {
 298     gdb_assert (ex.reason == RETURN_QUIT);
 299   }
 300 };
 301
 302 struct gdb_exception_forced_quit : public gdb_exception
 303 {
 304   gdb_exception_forced_quit (const char *fmt, va_list ap)
 305     ATTRIBUTE_PRINTF (2, 0)
 306     : gdb_exception (RETURN_FORCED_QUIT, GDB_NO_ERROR, fmt, ap)
 307   {
 308   }
 309
 310   explicit gdb_exception_forced_quit (gdb_exception &&ex) noexcept
 311     : gdb_exception (std::move (ex))
 312   {
 313     gdb_assert (ex.reason == RETURN_FORCED_QUIT);
 314   }
 315 };
 316
 317 /* An exception type that inherits from both std::bad_alloc and a gdb
 318    exception.  This is necessary because operator new can only throw
 319    std::bad_alloc, and OTOH, we want exceptions thrown due to memory
 320    allocation error to be caught by all the CATCH/RETURN_MASK_ALL
 321    spread around the codebase.  */
 322
 323 struct gdb_quit_bad_alloc
 324   : public gdb_exception_quit,
 325     public std::bad_alloc
 326 {
 327   explicit gdb_quit_bad_alloc (gdb_exception &&ex) noexcept
 328     : gdb_exception_quit (std::move (ex)),
 329       std::bad_alloc ()
 330   {
 331   }
 332 };
 333
 334 /* *INDENT-ON* */
 335
 336 /* Throw an exception (as described by "struct gdb_exception"),
 337    landing in the inner most containing exception handler established
 338    using TRY/CATCH.  */
 339 [[noreturn]] extern void throw_exception (gdb_exception &&exception);
 340
 341 /* Throw an exception by executing a LONG JUMP to the inner most
 342    containing exception handler established using TRY_SJLJ.  Necessary
 343    in some cases where we need to throw GDB exceptions across
 344    third-party library code (e.g., readline).  */
 345 [[noreturn]] extern void throw_exception_sjlj (const gdb_exception &exception);
 346
 347 /* Convenience wrappers around throw_exception that throw GDB
 348    errors.  */
 349 [[noreturn]] extern void throw_verror (enum errors, const char *fmt,
 350                                        va_list ap)
 351   ATTRIBUTE_PRINTF (2, 0);
 352 [[noreturn]] extern void throw_vquit (const char *fmt, va_list ap)
 353   ATTRIBUTE_PRINTF (1, 0);
 354 [[noreturn]] extern void throw_error (enum errors error, const char *fmt, ...)
 355   ATTRIBUTE_PRINTF (2, 3);
 356 [[noreturn]] extern void throw_quit (const char *fmt, ...)
 357   ATTRIBUTE_PRINTF (1, 2);
 358 [[noreturn]] [[noreturn]] extern void throw_forced_quit (const char *fmt, ...)
 359   ATTRIBUTE_PRINTF (1, 2);
 360
 361 #endif /* COMMON_COMMON_EXCEPTIONS_H */