Extended mruby binary format

The catch handler table is combined with iseq block.
This is to prevent the structure from growing by adding a field for the
catch handler table to the `mrb_irep` structure.

"iseq block" and "catch handler table":
  [number of catch handler table (2 bytes)]
  [number of byte code (4 bytes)]
  [iseq (any bytes)]
  [catch handlers (multiple of 7 bytes)]

catch handler:
  [catch type (1 byte)]
  [begin offset (2 bytes)]
  [end offset (2 bytes)]
  [target offset (2 bytes)]

catch type: enum mrb_catch_type (0 = rescue, 1 = ensure)
begin offset: Includes the specified instruction address
end offset: Does not include the specified instruction address
target offset: replaces pc with the specified instruction address

This table is not expanded by `read_irep_record_1()`.
The necessary elements are expanded one by one when used.

include/mruby/irep.h

@@ -39,13 +39,31 @@ typedef struct mrb_pool_value {
   } u;
 } mrb_pool_value;
 
+enum mrb_catch_type {
+  MRB_CATCH_RESCUE = 0,
+  MRB_CATCH_ENSURE = 1,
+};
+
+struct mrb_irep_catch_hander {
+  uint8_t type;         /* enum mrb_catch_type */
+  uint8_t begin[2];     /* The starting address to match the hander. Includes this. */
+  uint8_t end[2];       /* The endpoint address that matches the hander. Not Includes this. */
+  uint8_t target[2];    /* The address to jump to if a match is made. */
+};
+
 /* Program data array struct */
 typedef struct mrb_irep {
   uint16_t nlocals;        /* Number of local variables */
   uint16_t nregs;          /* Number of register variables */
+  uint16_t clen;           /* Number of catch handlers */
   uint8_t flags;
 
   const mrb_code *iseq;
+  /*
+   * A catch handler table is placed after the iseq entity.
+   * The reason it doesn't add fields to the structure is to keep the mrb_irep structure from bloating.
+   * The catch handler table can be obtained with `mrb_irep_catch_handler_table(irep)`.
+   */
   const mrb_pool_value *pool;
   const mrb_sym *syms;
   const struct mrb_irep * const *reps;
@@ -107,6 +125,17 @@ struct mrb_insn_data {
 
 struct mrb_insn_data mrb_decode_insn(const mrb_code *pc);
 
+static inline const struct mrb_irep_catch_hander *
+mrb_irep_catch_handler_table(const struct mrb_irep *irep)
+{
+  if (irep->clen > 0) {
+    return (const struct mrb_irep_catch_hander *)(irep->iseq + irep->ilen);
+  }
+  else {
+    return (const struct mrb_irep_catch_hander *)NULL;
+  }
+}
+
 MRB_END_DECL
 
 #endif  /* MRUBY_IREP_H */

mrbgems/mruby-compiler/core/codegen.c

@@ -11,6 +11,7 @@
 #include <mruby.h>
 #include <mruby/compile.h>
 #include <mruby/proc.h>
+#include <mruby/dump.h>
 #include <mruby/numeric.h>
 #include <mruby/string.h>
 #include <mruby/debug.h>
@@ -72,6 +73,7 @@ typedef struct scope {
   mrb_pool_value *pool;
   mrb_sym *syms;
   mrb_irep **reps;
+  struct mrb_irep_catch_hander *catch_table;
   uint32_t pcapa, scapa, rcapa;
 
   uint16_t nlocals;
@@ -91,6 +93,15 @@ static struct loopinfo *loop_push(codegen_scope *s, enum looptype t);
 static void loop_break(codegen_scope *s, node *tree);
 static void loop_pop(codegen_scope *s, int val);
 
+/*
+ * The search for catch handlers starts at the end of the table in mrb_vm_run().
+ * Therefore, the next handler to be added must meet one of the following conditions.
+ * - Larger start position
+ * - Same start position but smaller end position
+ */
+static int catch_hander_new(codegen_scope *s);
+static void catch_hander_set(codegen_scope *s, int ent, enum mrb_catch_type type, uint32_t begin, uint32_t end, uint32_t target);
+
 static void gen_assignment(codegen_scope *s, node *tree, int sp, int val);
 static void gen_vmassignment(codegen_scope *s, node *tree, int rhs, int val);
 
@@ -3082,9 +3093,18 @@ scope_finish(codegen_scope *s)
   }
   irep->flags = 0;
   if (s->iseq) {
-    irep->iseq = (const mrb_code *)codegen_realloc(s, s->iseq, sizeof(mrb_code)*s->pc);
+    size_t catchsize = sizeof(struct mrb_irep_catch_hander) * irep->clen;
+    irep->iseq = (const mrb_code *)codegen_realloc(s, s->iseq, sizeof(mrb_code)*s->pc + catchsize);
     irep->ilen = s->pc;
+    if (irep->clen > 0) {
+      memcpy((void *)(irep->iseq + irep->ilen), s->catch_table, catchsize);
+    }
   }
+  else {
+    irep->clen = 0;
+  }
+  mrb_free(s->mrb, s->catch_table);
+  s->catch_table = NULL;
   irep->pool = (const mrb_pool_value*)codegen_realloc(s, s->pool, sizeof(mrb_pool_value)*irep->plen);
   irep->syms = (const mrb_sym*)codegen_realloc(s, s->syms, sizeof(mrb_sym)*irep->slen);
   irep->reps = (const mrb_irep**)codegen_realloc(s, s->reps, sizeof(mrb_irep*)*irep->rlen);
@@ -3187,6 +3207,31 @@ loop_pop(codegen_scope *s, int val)
   if (val) push();
 }
 
+static int
+catch_hander_new(codegen_scope *s)
+{
+  size_t newsize = sizeof(struct mrb_irep_catch_hander) * (s->irep->clen + 1);
+  s->catch_table = (struct mrb_irep_catch_hander *)codegen_realloc(s, (void *)s->catch_table, newsize);
+  return s->irep->clen ++;
+}
+
+static void
+catch_hander_set(codegen_scope *s, int ent, enum mrb_catch_type type, uint32_t begin, uint32_t end, uint32_t target)
+{
+  struct mrb_irep_catch_hander *e;
+
+  mrb_assert(ent >= 0 && ent < s->irep->clen);
+  mrb_assert(begin < MAXARG_S);
+  mrb_assert(end < MAXARG_S);
+  mrb_assert(target < MAXARG_S);
+
+  e = &s->catch_table[ent];
+  uint8_to_bin(type, &e->type);
+  uint16_to_bin(begin, e->begin);
+  uint16_to_bin(end, e->end);
+  uint16_to_bin(target, e->target);
+}
+
 static struct RProc*
 generate_code(mrb_state *mrb, parser_state *p, int val)
 {

src/codedump.c

@@ -4,6 +4,7 @@
 #include <mruby/opcode.h>
 #include <mruby/string.h>
 #include <mruby/proc.h>
+#include <mruby/dump.h>
 
 #ifndef MRB_DISABLE_STDIO
 static void
@@ -80,6 +81,34 @@ codedump(mrb_state *mrb, const mrb_irep *irep)
     }
   }
 
+  if (irep->clen > 0) {
+    int i = irep->clen;
+    const struct mrb_irep_catch_hander *e = mrb_irep_catch_handler_table(irep);
+
+    for (; i > 0; i --, e ++) {
+      int begin = bin_to_uint16(e->begin);
+      int end = bin_to_uint16(e->end);
+      int target = bin_to_uint16(e->target);
+      char buf[20];
+      const char *type;
+
+      switch (e->type) {
+        case MRB_CATCH_RESCUE:
+          type = "rescue";
+          break;
+        case MRB_CATCH_ENSURE:
+          type = "ensure";
+          break;
+        default:
+          buf[0] = '\0';
+          snprintf(buf, sizeof(buf), "0x%02x <unknown>", (int)e->type);
+          type = buf;
+          break;
+      }
+      printf("catch type: %-8s begin: %04d end: %04d target: %04d\n", type, begin, end, target);
+    }
+  }
+
   pc = irep->iseq;
   pcend = pc + irep->ilen;
   while (pc < pcend) {

src/dump.c

@@ -273,6 +273,31 @@ write_syms_block(mrb_state *mrb, const mrb_irep *irep, uint8_t *buf)
   return cur - buf;
 }
 
+static size_t
+get_catch_table_block_size(mrb_state *mrb, const mrb_irep *irep)
+{
+  size_t size = 0;
+
+  size += sizeof(uint16_t); /* number of catch handler */
+  size += (sizeof(struct mrb_irep_catch_hander)) * irep->clen;
+
+  return size;
+}
+
+static ptrdiff_t
+write_catch_table_block(mrb_state *mrb, const mrb_irep *irep, uint8_t *buf)
+{
+  uint8_t *cur = buf;
+  const struct mrb_irep_catch_hander *e = mrb_irep_catch_handler_table(irep);
+  mrb_static_assert1(sizeof(*e) == 7);
+
+  /* irep->clen has already been written before iseq block */
+  memcpy(cur, (const void *)e, sizeof(*e) * irep->clen);
+  cur += sizeof(*e) * irep->clen;
+
+  return cur - buf;
+}
+
 static size_t
 get_irep_record_size_1(mrb_state *mrb, const mrb_irep *irep)
 {
@@ -280,6 +305,7 @@ get_irep_record_size_1(mrb_state *mrb, const mrb_irep *irep)
 
   size += get_irep_header_size(mrb);
   size += get_iseq_block_size(mrb, irep);
+  size += get_catch_table_block_size(mrb, irep);
   size += get_pool_block_size(mrb, irep);
   size += get_syms_block_size(mrb, irep);
   return size;
@@ -314,7 +340,13 @@ write_irep_record(mrb_state *mrb, const mrb_irep *irep, uint8_t *bin, size_t *ir
   }
 
   bin += write_irep_header(mrb, irep, bin);
+  /*
+   * The catch handler table is after iseq block, but the number of
+   * elements is placed before iseq block.
+   */
+  bin += uint16_to_bin(irep->clen, bin);
   bin += write_iseq_block(mrb, irep, bin, flags);
+  bin += write_catch_table_block(mrb, irep, bin);
   bin += write_pool_block(mrb, irep, bin);
   bin += write_syms_block(mrb, irep, bin);
 

src/load.c

@@ -96,27 +96,30 @@ read_irep_record_1(mrb_state *mrb, const uint8_t *bin, size_t *len, uint8_t flag
   src += sizeof(uint16_t);
 
   /* Binary Data Section */
-  /* ISEQ BLOCK */
+  /* ISEQ BLOCK (and CATCH HANDLER TABLE BLOCK) */
+  irep->clen = bin_to_uint16(src);  /* number of catch handler */
+  src += sizeof(uint16_t);
   irep->ilen = (uint16_t)bin_to_uint32(src);
   src += sizeof(uint32_t);
   src += skip_padding(src);
 
   if (irep->ilen > 0) {
+    size_t data_len = sizeof(mrb_code) * irep->ilen +
+                      sizeof(struct mrb_irep_catch_hander) * irep->clen;
+    mrb_static_assert1(sizeof(struct mrb_irep_catch_hander) == 7);
     if (SIZE_ERROR_MUL(irep->ilen, sizeof(mrb_code))) {
       return NULL;
     }
     if ((flags & FLAG_SRC_MALLOC) == 0) {
       irep->iseq = (mrb_code*)src;
-      src += sizeof(mrb_code) * irep->ilen;
       irep->flags |= MRB_ISEQ_NO_FREE;
     }
     else {
-      size_t data_len = sizeof(mrb_code) * irep->ilen;
       void *buf = mrb_malloc(mrb, data_len);
       irep->iseq = (mrb_code *)buf;
       memcpy(buf, src, data_len);
-      src += data_len;
     }
+    src += data_len;
   }
 
   /* POOL BLOCK */