gdb/common/common-exceptions.h

   1 /* Exception (throw catch) mechanism, for GDB, the GNU debugger.
   2
   3    Copyright (C) 1986-2019 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 #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 copy constructor exists so that we can mark it "noexcept",
 137      which is a good practice for any sort of exception object.  */
 138   gdb_exception (const gdb_exception &other) noexcept
 139     : reason (other.reason),
 140       error (other.error),
 141       message (other.message)
 142   {
 143   }
 144
 145   /* The assignment operator exists so that we can mark it "noexcept",
 146      which is a good practice for any sort of exception object.  */
 147   gdb_exception &operator= (const gdb_exception &other) noexcept
 148   {
 149     reason = other.reason;
 150     error = other.error;
 151     message = other.message;
 152     return *this;
 153   }
 154
 155   gdb_exception &operator= (gdb_exception &&other) noexcept = default;
 156
 157   /* Return the contents of the exception message, as a C string.  The
 158      string remains owned by the exception object.  */
 159   const char *what () const noexcept
 160   {
 161     return message->c_str ();
 162   }
 163
 164   enum return_reason reason;
 165   enum errors error;
 166   std::shared_ptr<std::string> message;
 167 };
 168
 169 /* Functions to drive the sjlj-based exceptions state machine.  Though
 170    declared here by necessity, these functions should be considered
 171    internal to the exceptions subsystem and not used other than via
 172    the TRY/CATCH (or TRY_SJLJ/CATCH_SJLJ) macros defined below.  */
 173
 174 extern jmp_buf *exceptions_state_mc_init (void);
 175 extern int exceptions_state_mc_action_iter (void);
 176 extern int exceptions_state_mc_action_iter_1 (void);
 177 extern int exceptions_state_mc_catch (struct gdb_exception *, int);
 178
 179 /* Macro to wrap up standard try/catch behavior.
 180
 181    The double loop lets us correctly handle code "break"ing out of the
 182    try catch block.  (It works as the "break" only exits the inner
 183    "while" loop, the outer for loop detects this handling it
 184    correctly.)  Of course "return" and "goto" are not so lucky.
 185
 186    For instance:
 187
 188    *INDENT-OFF*
 189
 190    TRY_SJLJ
 191      {
 192      }
 193    CATCH_SJLJ (e, RETURN_MASK_ERROR)
 194      {
 195        switch (e.reason)
 196          {
 197            case RETURN_ERROR: ...
 198          }
 199      }
 200    END_CATCH_SJLJ
 201
 202    The SJLJ variants are needed in some cases where gdb exceptions
 203    need to cross third-party library code compiled without exceptions
 204    support (e.g., readline).  */
 205
 206 #define TRY_SJLJ \
 207      { \
 208        jmp_buf *buf = \
 209          exceptions_state_mc_init (); \
 210        setjmp (*buf); \
 211      } \
 212      while (exceptions_state_mc_action_iter ()) \
 213        while (exceptions_state_mc_action_iter_1 ())
 214
 215 #define CATCH_SJLJ(EXCEPTION, MASK)                             \
 216   {                                                     \
 217     struct gdb_exception EXCEPTION;                             \
 218     if (exceptions_state_mc_catch (&(EXCEPTION), MASK))
 219
 220 #define END_CATCH_SJLJ                          \
 221   }
 222
 223 /* The exception types client code may catch.  They're just shims
 224    around gdb_exception that add nothing but type info.  Which is used
 225    is selected depending on the MASK argument passed to CATCH.  */
 226
 227 struct gdb_exception_error : public gdb_exception
 228 {
 229   gdb_exception_error (enum errors e, const char *fmt, va_list ap)
 230     ATTRIBUTE_PRINTF (3, 0)
 231     : gdb_exception (RETURN_ERROR, e, fmt, ap)
 232   {
 233   }
 234
 235   explicit gdb_exception_error (const gdb_exception &ex) noexcept
 236     : gdb_exception (ex)
 237   {
 238     gdb_assert (ex.reason == RETURN_ERROR);
 239   }
 240 };
 241
 242 struct gdb_exception_quit : public gdb_exception
 243 {
 244   gdb_exception_quit (const char *fmt, va_list ap)
 245     ATTRIBUTE_PRINTF (2, 0)
 246     : gdb_exception (RETURN_QUIT, GDB_NO_ERROR, fmt, ap)
 247   {
 248   }
 249
 250   explicit gdb_exception_quit (const gdb_exception &ex) noexcept
 251     : gdb_exception (ex)
 252   {
 253     gdb_assert (ex.reason == RETURN_QUIT);
 254   }
 255 };
 256
 257 /* An exception type that inherits from both std::bad_alloc and a gdb
 258    exception.  This is necessary because operator new can only throw
 259    std::bad_alloc, and OTOH, we want exceptions thrown due to memory
 260    allocation error to be caught by all the CATCH/RETURN_MASK_ALL
 261    spread around the codebase.  */
 262
 263 struct gdb_quit_bad_alloc
 264   : public gdb_exception_quit,
 265     public std::bad_alloc
 266 {
 267   explicit gdb_quit_bad_alloc (const gdb_exception &ex) noexcept
 268     : gdb_exception_quit (ex),
 269       std::bad_alloc ()
 270   {
 271   }
 272 };
 273
 274 /* *INDENT-ON* */
 275
 276 /* Throw an exception (as described by "struct gdb_exception"),
 277    landing in the inner most containing exception handler established
 278    using TRY/CATCH.  */
 279 extern void throw_exception (const gdb_exception &exception)
 280      ATTRIBUTE_NORETURN;
 281
 282 /* Throw an exception by executing a LONG JUMP to the inner most
 283    containing exception handler established using TRY_SJLJ.  Necessary
 284    in some cases where we need to throw GDB exceptions across
 285    third-party library code (e.g., readline).  */
 286 extern void throw_exception_sjlj (const struct gdb_exception &exception)
 287      ATTRIBUTE_NORETURN;
 288
 289 /* Convenience wrappers around throw_exception that throw GDB
 290    errors.  */
 291 extern void throw_verror (enum errors, const char *fmt, va_list ap)
 292      ATTRIBUTE_NORETURN ATTRIBUTE_PRINTF (2, 0);
 293 extern void throw_vquit (const char *fmt, va_list ap)
 294      ATTRIBUTE_NORETURN ATTRIBUTE_PRINTF (1, 0);
 295 extern void throw_error (enum errors error, const char *fmt, ...)
 296      ATTRIBUTE_NORETURN ATTRIBUTE_PRINTF (2, 3);
 297 extern void throw_quit (const char *fmt, ...)
 298      ATTRIBUTE_NORETURN ATTRIBUTE_PRINTF (1, 2);
 299
 300 #endif /* COMMON_COMMON_EXCEPTIONS_H */