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  93      aborted as the inferior state is no longer valid.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