libguile/control.c

   1 /* Copyright (C) 2010, 2011, 2012  Free Software Foundation, Inc.
   2  *
   3  * This library is free software; you can redistribute it and/or
   4  * modify it under the terms of the GNU Lesser General Public License
   5  * as published by the Free Software Foundation; either version 3 of
   6  * the License, or (at your option) any later version.
   7  *
   8  * This library is distributed in the hope that it will be useful, but
   9  * WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  11  * Lesser General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU Lesser General Public
  14  * License along with this library; if not, write to the Free Software
  15  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  16  * 02110-1301 USA
  17  */
  18
  19 #if HAVE_CONFIG_H
  20 #  include <config.h>
  21 #endif
  22
  23 #include <alloca.h>
  24
  25 #include "libguile/_scm.h"
  26 #include "libguile/control.h"
  27 #include "libguile/objcodes.h"
  28 #include "libguile/instructions.h"
  29 #include "libguile/vm.h"
  30
  31 \f
  32
  33 #define PROMPT_ESCAPE_P(p)                              \
  34   (SCM_DYNSTACK_TAG_FLAGS (SCM_DYNSTACK_TAG (p))        \
  35    & SCM_F_DYNSTACK_PROMPT_ESCAPE_ONLY)
  36
  37 \f
  38
  39
  40 /* Only to be called if the SCM_I_SETJMP returns 1 */
  41 SCM
  42 scm_i_prompt_pop_abort_args_x (SCM vm)
  43 {
  44   size_t i, n;
  45   SCM vals = SCM_EOL;
  46
  47   n = scm_to_size_t (SCM_VM_DATA (vm)->sp[0]);
  48   for (i = 0; i < n; i++)
  49     vals = scm_cons (SCM_VM_DATA (vm)->sp[-(i + 1)], vals);
  50
  51   /* The abort did reset the VM's registers, but then these values
  52      were pushed on; so we need to pop them ourselves. */
  53   SCM_VM_DATA (vm)->sp -= n + 1;
  54   /* FIXME NULLSTACK */
  55
  56   return vals;
  57 }
  58
  59
  60 #ifdef WORDS_BIGENDIAN
  61 #define OBJCODE_HEADER(main,meta) 0, 0, 0, main, 0, 0, 0, meta+8
  62 #define META_HEADER(meta)         0, 0, 0, meta, 0, 0, 0, 0
  63 #else
  64 #define OBJCODE_HEADER(main,meta) main, 0, 0, 0, meta+8, 0, 0, 0
  65 #define META_HEADER(meta)         meta, 0, 0, 0, 0,      0, 0, 0
  66 #endif
  67
  68 #define OBJCODE_TAG SCM_MAKE_OBJCODE_TAG (SCM_OBJCODE_TYPE_STATIC, 0)
  69
  70 #if defined (SCM_ALIGNED)
  71 #define SCM_DECLARE_STATIC_ALIGNED_ARRAY(type, sym)     \
  72 static const type sym[]
  73 #define SCM_STATIC_ALIGNED_ARRAY(alignment, type, sym)  \
  74 static SCM_ALIGNED (alignment) const type sym[]
  75 #define SCM_STATIC_OBJCODE(sym)                                         \
  76   SCM_DECLARE_STATIC_ALIGNED_ARRAY (scm_t_uint8, sym##__bytecode);      \
  77   SCM_STATIC_ALIGNED_ARRAY (8, scm_t_cell, sym##__cells) = {            \
  78     { SCM_PACK (OBJCODE_TAG), SCM_PACK (sym##__bytecode) },             \
  79     { SCM_BOOL_F, SCM_PACK (0) }                                        \
  80   };                                                                    \
  81   static const SCM sym = SCM_PACK (sym##__cells);                       \
  82   SCM_STATIC_ALIGNED_ARRAY (8, scm_t_uint8, sym##__bytecode)
  83 #else
  84 #define SCM_STATIC_OBJCODE(sym)                                         \
  85 static SCM sym;                                                         \
  86 static scm_t_uint8 *sym##_bytecode;                                     \
  87 SCM_SNARF_INIT(sym##_bytecode = scm_gc_malloc_pointerless (sizeof(sym##_bytecode__unaligned), "partial continuation stub"); \
  88                memcpy (sym##_bytecode, sym##_bytecode__unaligned, sizeof(sym##_bytecode__unaligned));) \
  89 SCM_SNARF_INIT(sym = scm_double_cell (OBJCODE_TAG,                      \
  90                                       (scm_t_bits)sym##_bytecode,       \
  91                                       SCM_UNPACK (SCM_BOOL_F),          \
  92                                       0);)                              \
  93 static const scm_t_uint8 sym##_bytecode__unaligned[]
  94 #endif
  95
  96
  97 SCM_STATIC_OBJCODE (cont_objcode) = {
  98   /* Like in continuations.c, but with partial-cont-call. */
  99   OBJCODE_HEADER (8, 19),
 100   /* leave args on the stack */
 101   /* 0 */ scm_op_object_ref, 0, /* push scm_vm_cont object */
 102   /* 2 */ scm_op_partial_cont_call, /* and go! */
 103   /* 3 */ scm_op_nop,
 104   /* 4 */ scm_op_nop, scm_op_nop, scm_op_nop, scm_op_nop, /* pad to 8 bytes */
 105   /* 8 */
 106
 107   /* We could put some meta-info to say that this proc is a continuation. Not sure
 108      how to do that, though. */
 109   META_HEADER (19),
 110   /* 0 */ scm_op_make_eol, /* bindings */
 111   /* 1 */ scm_op_make_eol, /* sources */
 112   /* 2 */ scm_op_make_int8, 0, scm_op_make_int8, 3, /* arity: from ip 0 to ip 3 */
 113   /* 6 */ scm_op_make_int8_0, /* the arity is 0 required args */
 114   /* 7 */ scm_op_make_int8_0, /* 0 optionals */
 115   /* 8 */ scm_op_make_true, /* and a rest arg */
 116   /* 9 */ scm_op_list, 0, 5, /* make a list of those 5 vals */
 117   /* 12 */ scm_op_list, 0, 1, /* and the arities will be a list of that one list */
 118   /* 15 */ scm_op_list, 0, 3, /* pack bindings, sources, and arities into list */
 119   /* 18 */ scm_op_return /* and return */
 120   /* 19 */
 121 };
 122
 123
 124 static SCM
 125 reify_partial_continuation (SCM vm,
 126                             SCM *saved_fp, SCM *saved_sp, scm_t_uint8 *saved_ip,
 127                             scm_i_jmp_buf *saved_registers,
 128                             scm_t_dynstack *dynstack,
 129                             scm_i_jmp_buf *current_registers)
 130 {
 131   SCM vm_cont, ret;
 132   scm_t_uint32 flags;
 133
 134   flags = SCM_F_VM_CONT_PARTIAL;
 135   /* If we are aborting to a prompt that has the same registers as those
 136      of the abort, it means there are no intervening C frames on the
 137      stack, and so the continuation can be relocated elsewhere on the
 138      stack: it is rewindable.  */
 139   if (saved_registers && saved_registers == current_registers)
 140     flags |= SCM_F_VM_CONT_REWINDABLE;
 141
 142   /* Since non-escape continuations should begin with a thunk application, the
 143      first bit of the stack should be a frame, with the saved fp equal to the fp
 144      that was current when the prompt was made. */
 145   if ((SCM*)SCM_UNPACK (saved_sp[1]) != saved_fp)
 146     abort ();
 147
 148   /* Capture from the top of the thunk application frame up to the end. Set an
 149      MVRA only, as the post-abort code is in an MV context. */
 150   vm_cont = scm_i_vm_capture_stack (saved_sp + 4,
 151                                     SCM_VM_DATA (vm)->fp,
 152                                     SCM_VM_DATA (vm)->sp,
 153                                     NULL,
 154                                     SCM_VM_DATA (vm)->ip,
 155                                     dynstack,
 156                                     flags);
 157
 158   ret = scm_make_program (cont_objcode,
 159                           scm_c_make_vector (1, vm_cont),
 160                           SCM_BOOL_F);
 161   SCM_SET_CELL_WORD_0 (ret,
 162                        SCM_CELL_WORD_0 (ret) | SCM_F_PROGRAM_IS_PARTIAL_CONTINUATION);
 163   return ret;
 164 }
 165
 166 void
 167 scm_c_abort (SCM vm, SCM tag, size_t n, SCM *argv,
 168              scm_i_jmp_buf *current_registers)
 169 {
 170   SCM cont;
 171   scm_t_dynstack *dynstack = &SCM_I_CURRENT_THREAD->dynstack;
 172   scm_t_bits *prompt;
 173   scm_t_dynstack_prompt_flags flags;
 174   SCM *fp, *sp;
 175   scm_t_uint8 *ip;
 176   scm_i_jmp_buf *registers;
 177   size_t i;
 178
 179   prompt = scm_dynstack_find_prompt (dynstack, tag,
 180                                      &flags, &fp, &sp, &ip, &registers);
 181
 182   if (!prompt)
 183     scm_misc_error ("abort", "Abort to unknown prompt", scm_list_1 (tag));
 184
 185   /* Only reify if the continuation referenced in the handler. */
 186   if (flags & SCM_F_DYNSTACK_PROMPT_ESCAPE_ONLY)
 187     cont = SCM_BOOL_F;
 188   else
 189     {
 190       scm_t_dynstack *captured;
 191
 192       captured = scm_dynstack_capture (dynstack, SCM_DYNSTACK_NEXT (prompt));
 193       cont = reify_partial_continuation (vm, fp, sp, ip, registers, captured,
 194                                          current_registers);
 195     }
 196
 197   /* Unwind.  */
 198   scm_dynstack_unwind (dynstack, prompt);
 199
 200   /* Unwinding may have changed the current thread's VM, so use the
 201      new one.  */
 202   vm = scm_the_vm ();
 203
 204   /* Restore VM regs */
 205   SCM_VM_DATA (vm)->fp = fp;
 206   SCM_VM_DATA (vm)->sp = sp;
 207   SCM_VM_DATA (vm)->ip = ip;
 208
 209   /* Since we're jumping down, we should always have enough space.  */
 210   if (SCM_VM_DATA (vm)->sp + n + 1 >= SCM_VM_DATA (vm)->stack_limit)
 211     abort ();
 212
 213   /* Push vals */
 214   *(++(SCM_VM_DATA (vm)->sp)) = cont;
 215   for (i = 0; i < n; i++)
 216     *(++(SCM_VM_DATA (vm)->sp)) = argv[i];
 217   *(++(SCM_VM_DATA (vm)->sp)) = scm_from_size_t (n+1); /* +1 for continuation */
 218
 219   /* Jump! */
 220   SCM_I_LONGJMP (*registers, 1);
 221
 222   /* Shouldn't get here */
 223   abort ();
 224 }
 225
 226 SCM_DEFINE (scm_at_abort, "@abort", 2, 0, 0, (SCM tag, SCM args),
 227             "Abort to the nearest prompt with tag @var{tag}.")
 228 #define FUNC_NAME s_scm_at_abort
 229 {
 230   SCM *argv;
 231   size_t i;
 232   long n;
 233
 234   SCM_VALIDATE_LIST_COPYLEN (SCM_ARG2, args, n);
 235   argv = alloca (sizeof (SCM)*n);
 236   for (i = 0; i < n; i++, args = scm_cdr (args))
 237     argv[i] = scm_car (args);
 238
 239   scm_c_abort (scm_the_vm (), tag, n, argv, NULL);
 240
 241   /* Oh, what, you're still here? The abort must have been reinstated. Actually,
 242      that's quite impossible, given that we're already in C-land here, so...
 243      abort! */
 244
 245   abort ();
 246 }
 247 #undef FUNC_NAME
 248
 249 void
 250 scm_init_control (void)
 251 {
 252 #include "libguile/control.x"
 253 }
 254
 255 /*
 256   Local Variables:
 257   c-file-style: "gnu"
 258   End:
 259 */