gdbsupport/common-exceptions.h

   1 /* Exception (throw catch) mechanism, for GDB, the GNU debugger.
   2
   3    Copyright (C) 1986-2021 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
  28 /* Reasons for calling throw_exceptions().  NOTE: all reason values
  29    must be different from zero.  enum value 0 is reserved for internal
  30    use as the return value from an initial setjmp().  */
  31
  32 enum return_reason
  33   {
  34     /* User interrupt.  */
  35     RETURN_QUIT = -2,
  36     /* Any other error.  */
  37     RETURN_ERROR
  38   };
  39
  40 #define RETURN_MASK(reason)     (1 << (int)(-reason))
  41
  42 typedef enum
  43 {
  44   RETURN_MASK_QUIT = RETURN_MASK (RETURN_QUIT),
  45   RETURN_MASK_ERROR = RETURN_MASK (RETURN_ERROR),
  46   RETURN_MASK_ALL = (RETURN_MASK_QUIT | RETURN_MASK_ERROR)
  47 } return_mask;
  48
  49 /* Describe all exceptions.  */
  50
  51 enum errors {
  52   GDB_NO_ERROR,
  53
  54   /* Any generic error, the corresponding text is in
  55      exception.message.  */
  56   GENERIC_ERROR,
  57
  58   /* Something requested was not found.  */
  59   NOT_FOUND_ERROR,
  60
  61   /* Thread library lacks support necessary for finding thread local
  62      storage.  */
  63   TLS_NO_LIBRARY_SUPPORT_ERROR,
  64
  65   /* Load module not found while attempting to find thread local storage.  */
  66   TLS_LOAD_MODULE_NOT_FOUND_ERROR,
  67
  68   /* Thread local storage has not been allocated yet.  */
  69   TLS_NOT_ALLOCATED_YET_ERROR,
  70
  71   /* Something else went wrong while attempting to find thread local
  72      storage.  The ``struct gdb_exception'' message field provides
  73      more detail.  */
  74   TLS_GENERIC_ERROR,
  75
  76   /* Problem parsing an XML document.  */
  77   XML_PARSE_ERROR,
  78
  79   /* Error accessing memory.  */
  80   MEMORY_ERROR,
  81
  82   /* Value not available.  E.g., a register was not collected in a
  83      traceframe.  */
  84   NOT_AVAILABLE_ERROR,
  85
  86   /* Value was optimized out.  Note: if the value was a register, this
  87      means the register was not saved in the frame.  */
  88   OPTIMIZED_OUT_ERROR,
  89
  90   /* DW_OP_entry_value resolving failed.  */
  91   NO_ENTRY_VALUE_ERROR,
  92
  93   /* Target throwing an error has been closed.  Current command should be
  94      aborted as the inferior state is no longer valid.  */
  95   TARGET_CLOSE_ERROR,
  96
  97   /* An undefined command was executed.  */
  98   UNDEFINED_COMMAND_ERROR,
  99
 100   /* Requested feature, method, mechanism, etc. is not supported.  */
 101   NOT_SUPPORTED_ERROR,
 102
 103   /* The number of candidates generated during line completion has
 104      reached the user's specified limit.  This isn't an error, this exception
 105      is used to halt searching for more completions, but for consistency
 106      "_ERROR" is appended to the name.  */
 107   MAX_COMPLETIONS_REACHED_ERROR,
 108
 109   /* Add more errors here.  */
 110   NR_ERRORS
 111 };
 112
 113 struct gdb_exception
 114 {
 115   gdb_exception ()
 116     : reason ((enum return_reason) 0),
 117       error (GDB_NO_ERROR)
 118   {
 119   }
 120
 121   gdb_exception (enum return_reason r, enum errors e)
 122     : reason (r),
 123       error (e)
 124   {
 125   }
 126
 127   gdb_exception (enum return_reason r, enum errors e,
 128                  const char *fmt, va_list ap)
 129     ATTRIBUTE_PRINTF (4, 0)
 130     : reason (r),
 131       error (e),
 132       message (std::make_shared<std::string> (string_vprintf (fmt, ap)))
 133   {
 134   }
 135
 136   /* The move constructor exists so that we can mark it "noexcept",
 137      which is a good practice for any sort of exception object.  */
 138   explicit gdb_exception (gdb_exception &&other) noexcept = default;
 139
 140   /* The copy constructor exists so that we can mark it "noexcept",
 141      which is a good practice for any sort of exception object.  */
 142   gdb_exception (const gdb_exception &other) noexcept
 143     : reason (other.reason),
 144       error (other.error),
 145       message (other.message)
 146   {
 147   }
 148
 149   /* The assignment operator exists so that we can mark it "noexcept",
 150      which is a good practice for any sort of exception object.  */
 151   gdb_exception &operator= (const gdb_exception &other) noexcept
 152   {
 153     reason = other.reason;
 154     error = other.error;
 155     message = other.message;
 156     return *this;
 157   }
 158
 159   gdb_exception &operator= (gdb_exception &&other) noexcept = default;
 160
 161   /* Return the contents of the exception message, as a C string.  The
 162      string remains owned by the exception object.  */
 163   const char *what () const noexcept
 164   {
 165     return message->c_str ();
 166   }
 167
 168   /* Compare two exceptions.  */
 169   bool operator== (const gdb_exception &other) const
 170   {
 171     const char *msg1 = message == nullptr ? "" : what ();
 172     const char *msg2 = other.message == nullptr ? "" : other.what ();
 173
 174     return (reason == other.reason
 175             && error == other.error
 176             && strcmp (msg1, msg2) == 0);
 177   }
 178
 179   /* Compare two exceptions.  */
 180   bool operator!= (const gdb_exception &other) const
 181   {
 182     return !(*this == other);
 183   }
 184
 185   enum return_reason reason;
 186   enum errors error;
 187   std::shared_ptr<std::string> message;
 188 };
 189
 190 /* Functions to drive the sjlj-based exceptions state machine.  Though
 191    declared here by necessity, these functions should be considered
 192    internal to the exceptions subsystem and not used other than via
 193    the TRY/CATCH (or TRY_SJLJ/CATCH_SJLJ) macros defined below.  */
 194
 195 extern jmp_buf *exceptions_state_mc_init (void);
 196 extern int exceptions_state_mc_action_iter (void);
 197 extern int exceptions_state_mc_action_iter_1 (void);
 198 extern int exceptions_state_mc_catch (struct gdb_exception *, int);
 199
 200 /* Macro to wrap up standard try/catch behavior.
 201
 202    The double loop lets us correctly handle code "break"ing out of the
 203    try catch block.  (It works as the "break" only exits the inner
 204    "while" loop, the outer for loop detects this handling it
 205    correctly.)  Of course "return" and "goto" are not so lucky.
 206
 207    For instance:
 208
 209    *INDENT-OFF*
 210
 211    TRY_SJLJ
 212      {
 213      }
 214    CATCH_SJLJ (e, RETURN_MASK_ERROR)
 215      {
 216        switch (e.reason)
 217          {
 218            case RETURN_ERROR: ...
 219          }
 220      }
 221    END_CATCH_SJLJ
 222
 223    The SJLJ variants are needed in some cases where gdb exceptions
 224    need to cross third-party library code compiled without exceptions
 225    support (e.g., readline).  */
 226
 227 #define TRY_SJLJ \
 228      { \
 229        jmp_buf *buf = \
 230          exceptions_state_mc_init (); \
 231        setjmp (*buf); \
 232      } \
 233      while (exceptions_state_mc_action_iter ()) \
 234        while (exceptions_state_mc_action_iter_1 ())
 235
 236 #define CATCH_SJLJ(EXCEPTION, MASK)                             \
 237   {                                                     \
 238     struct gdb_exception EXCEPTION;                             \
 239     if (exceptions_state_mc_catch (&(EXCEPTION), MASK))
 240
 241 #define END_CATCH_SJLJ                          \
 242   }
 243
 244 /* The exception types client code may catch.  They're just shims
 245    around gdb_exception that add nothing but type info.  Which is used
 246    is selected depending on the MASK argument passed to CATCH.  */
 247
 248 struct gdb_exception_error : public gdb_exception
 249 {
 250   gdb_exception_error (enum errors e, const char *fmt, va_list ap)
 251     ATTRIBUTE_PRINTF (3, 0)
 252     : gdb_exception (RETURN_ERROR, e, fmt, ap)
 253   {
 254   }
 255
 256   explicit gdb_exception_error (gdb_exception &&ex) noexcept
 257     : gdb_exception (std::move (ex))
 258   {
 259     gdb_assert (ex.reason == RETURN_ERROR);
 260   }
 261 };
 262
 263 struct gdb_exception_quit : public gdb_exception
 264 {
 265   gdb_exception_quit (const char *fmt, va_list ap)
 266     ATTRIBUTE_PRINTF (2, 0)
 267     : gdb_exception (RETURN_QUIT, GDB_NO_ERROR, fmt, ap)
 268   {
 269   }
 270
 271   explicit gdb_exception_quit (gdb_exception &&ex) noexcept
 272     : gdb_exception (std::move (ex))
 273   {
 274     gdb_assert (ex.reason == RETURN_QUIT);
 275   }
 276 };
 277
 278 /* An exception type that inherits from both std::bad_alloc and a gdb
 279    exception.  This is necessary because operator new can only throw
 280    std::bad_alloc, and OTOH, we want exceptions thrown due to memory
 281    allocation error to be caught by all the CATCH/RETURN_MASK_ALL
 282    spread around the codebase.  */
 283
 284 struct gdb_quit_bad_alloc
 285   : public gdb_exception_quit,
 286     public std::bad_alloc
 287 {
 288   explicit gdb_quit_bad_alloc (gdb_exception &&ex) noexcept
 289     : gdb_exception_quit (std::move (ex)),
 290       std::bad_alloc ()
 291   {
 292   }
 293 };
 294
 295 /* *INDENT-ON* */
 296
 297 /* Throw an exception (as described by "struct gdb_exception"),
 298    landing in the inner most containing exception handler established
 299    using TRY/CATCH.  */
 300 extern void throw_exception (gdb_exception &&exception)
 301      ATTRIBUTE_NORETURN;
 302
 303 /* Throw an exception by executing a LONG JUMP to the inner most
 304    containing exception handler established using TRY_SJLJ.  Necessary
 305    in some cases where we need to throw GDB exceptions across
 306    third-party library code (e.g., readline).  */
 307 extern void throw_exception_sjlj (const struct gdb_exception &exception)
 308      ATTRIBUTE_NORETURN;
 309
 310 /* Convenience wrappers around throw_exception that throw GDB
 311    errors.  */
 312 extern void throw_verror (enum errors, const char *fmt, va_list ap)
 313      ATTRIBUTE_NORETURN ATTRIBUTE_PRINTF (2, 0);
 314 extern void throw_vquit (const char *fmt, va_list ap)
 315      ATTRIBUTE_NORETURN ATTRIBUTE_PRINTF (1, 0);
 316 extern void throw_error (enum errors error, const char *fmt, ...)
 317      ATTRIBUTE_NORETURN ATTRIBUTE_PRINTF (2, 3);
 318 extern void throw_quit (const char *fmt, ...)
 319      ATTRIBUTE_NORETURN ATTRIBUTE_PRINTF (1, 2);
 320
 321 #endif /* COMMON_COMMON_EXCEPTIONS_H */