gcc/eh-common.h

   1 /* EH stuff
   2    Copyright (C) 1997, 1998, 1999, 2000 Free Software Foundation, Inc.
   3
   4 This file is part of GNU CC.
   5
   6 This program is free software; you can redistribute it and/or modify it
   7 under the terms of the GNU General Public License as published by the
   8 Free Software Foundation; either version 2, or (at your option) any
   9 later version.
  10
  11 This program is distributed in the hope that it will be useful,
  12 but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 GNU General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with this program; if not, write to the Free Software
  18 Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  19
  20
  21 /* This file contains the structures required for the language
  22    independent exception handling model. Both the static compiler and
  23    the runtime library share this file. */
  24
  25 /* The runtime flag flag_new_exceptions is used to determine whether the
  26    compiler supports the new runtime typechecking mechanism or not. Under
  27    the new model, runtime info is contained in the exception table, and
  28    the __throw() library routine determines which handler to call based
  29    on the results of a call to a matching function provided by the expcetion
  30    thrower.  Otherwise the old scheme of calling any handler which matches
  31    an exception range is used, and the handler is responsible for all
  32    checking of runtime conditions. If the handler wasn't suppose to
  33    get the exception, it performs a re-throw. */
  34
  35
  36 /* The handler_label field MUST be the first field in this structure. The
  37    __throw()  library routine expects uses __eh_stub() from except.c, which
  38    simply dereferences the context pointer to get the handler.
  39    The routine get_dynamic_handler_chain() also has a dependancy on
  40    the location of 'dynamic_handler_chain'. If its location is changed,
  41    that routine must be modified as well. */
  42 #ifndef EH_ALLOC_SIZE
  43 /* 192 bytes means the entire eh_context plus malloc overhead fits in 256
  44    bytes (assuming 8 byte pointers). 192 bytes gives an eh_info and object
  45    size limit of 96 bytes. This should be sufficient for throwing bad_alloc. */
  46 #define EH_ALLOC_SIZE 192
  47 #endif
  48 #ifndef EH_ALLOC_ALIGN
  49 /* We can't use BIGGEST_ALIGNMENT, because on some systems, that expands to
  50    a check on a compile time switch like
  51    'target_flags & MASK_ALIGN_DOUBLE ? 64 : 32'. There's no macro for
  52    'largest alignment for any code this compiler can build for', which is
  53    really what is needed. */
  54 #define EH_ALLOC_ALIGN 16
  55 #endif
  56
  57 struct eh_context
  58 {
  59   void *handler_label;
  60   void **dynamic_handler_chain;
  61   /* This is language dependent part of the eh context. */
  62   void *info;
  63   /* This is used to remember where we threw for re-throws */
  64   void *table_index;  /* address of exception table entry to rethrow from */
  65   /* emergency fallback space, if malloc fails during handling */
  66   char alloc_buffer[EH_ALLOC_SIZE]
  67       __attribute__((__aligned__(EH_ALLOC_ALIGN)));
  68   unsigned alloc_mask;
  69 };
  70
  71 #ifndef EH_TABLE_LOOKUP
  72
  73 typedef struct old_exception_table
  74 {
  75   void *start_region;
  76   void *end_region;
  77   void *exception_handler;
  78 } old_exception_table;
  79
  80 typedef struct exception_table
  81 {
  82   void *start_region;
  83   void *end_region;
  84   void *exception_handler;
  85   void *match_info;              /* runtime type info */
  86 } exception_table;
  87
  88
  89 /* The language identifying portion of an exception table */
  90
  91 typedef struct exception_lang_info
  92 {
  93   short language;
  94   short version;
  95 } exception_lang_info;
  96
  97 /* This value in the first field of the exception descriptor
  98    identifies the descriptor as the new model format. This value would never
  99    be present in this location under the old model */
 100
 101 #define NEW_EH_RUNTIME  ((void *) -2)
 102
 103 /* Each function has an exception_descriptor which contains the
 104    language info, and a table of exception ranges and handlers */
 105
 106 typedef struct exception_descriptor
 107 {
 108   void *runtime_id_field;
 109   exception_lang_info lang;
 110   exception_table table[1];
 111 } exception_descriptor;
 112
 113 struct __eh_info; /* forward declaration */
 114
 115 /* A pointer to a matching function is initialized at runtime by the
 116    specific language if run-time exceptions are supported.
 117    The function takes 3 parameters
 118     1 - runtime exception that has been thrown info. (__eh_info *)
 119     2 - Match info pointer from the region being considered (void *)
 120     3 - exception table region is in (exception descriptor *)
 121 */
 122
 123 typedef void * (*__eh_matcher)  PARAMS ((struct __eh_info *, void *,
 124                                          struct exception_descriptor *));
 125
 126 /* This value is to be checked as a 'match all' case in the runtime field. */
 127
 128 #define CATCH_ALL_TYPE   ((void *) -1)
 129
 130 /* This is the runtime exception information. This forms the minimum required
 131    information for an exception info pointer in an eh_context structure. */
 132
 133
 134 typedef struct __eh_info
 135 {
 136   __eh_matcher match_function;
 137   short language;
 138   short version;
 139 } __eh_info;
 140
 141 /* Convienient language codes for ID the originating language. Similar
 142    to the codes in dwarf2.h. */
 143
 144 enum exception_source_language
 145   {
 146     EH_LANG_C89 = 0x0001,
 147     EH_LANG_C = 0x0002,
 148     EH_LANG_Ada83 = 0x0003,
 149     EH_LANG_C_plus_plus = 0x0004,
 150     EH_LANG_Cobol74 = 0x0005,
 151     EH_LANG_Cobol85 = 0x0006,
 152     EH_LANG_Fortran77 = 0x0007,
 153     EH_LANG_Fortran90 = 0x0008,
 154     EH_LANG_Pascal83 = 0x0009,
 155     EH_LANG_Modula2 = 0x000a,
 156     EH_LANG_Java = 0x000b,
 157     EH_LANG_Mips_Assembler = 0x8001
 158   };
 159
 160 #endif  /* EH_TABLE_LOOKUP */
 161
 162