path: root/src/wasm-check.c

#include <assert.h>
#include <memory.h>
#include <stdarg.h>
#include <stdio.h>

#include "wasm.h"
#include "wasm-internal.h"

static const char* s_type_names[] = {
    "void",
    "i32",
    "i64",
    "i32 or i64",
    "f32",
    "i32 or f32",
    "i64 or f32",
    "i32, i64 or f32",
    "f64",
    "i32 or f64",
    "i64 or f64",
    "i32, i64 or f64",
    "f32 or f64",
    "i32, f32 or f64",
    "i64, f32 or f64",
    "i32, i64, f32 or f64",
};
STATIC_ASSERT(ARRAY_SIZE(s_type_names) == WASM_TYPE_ALL + 1);

typedef struct WasmLabelNode {
  WasmLabel* label;
  int depth;
  WasmType expected_type;
  const char* desc;
  struct WasmLabelNode* next;
} WasmLabelNode;

typedef struct WasmCheckContext {
  WasmModule* last_module;
  WasmLabelNode* top_label;
  int in_assert_invalid;
} WasmCheckContext;

static void print_error(WasmCheckContext* ctx,
                        WasmLocation* loc,
                        const char* fmt,
                        ...) {
  va_list args;
  va_start(args, fmt);
  FILE* out = stderr;
  if (ctx->in_assert_invalid) {
    out = stdout;
    fprintf(out, "assert_invalid error:\n  ");
  }
  if (loc)
    fprintf(out, "%s:%d:%d: ", loc->filename, loc->first_line,
            loc->first_column);
  vfprintf(out, fmt, args);
  fprintf(out, "\n");
}

static int string_slices_are_equal(WasmStringSlice* a, WasmStringSlice* b) {
  return a->start && b->start && a->length == b->length &&
         memcmp(a->start, b->start, a->length) == 0;
}

static int find_binding_index_by_name(WasmBindingVector* bindings,
                                      WasmStringSlice* name) {
  int i;
  for (i = 0; i < bindings->size; ++i)
    if (string_slices_are_equal(name, &bindings->data[i].name))
      return bindings->data[i].index;
  return -1;
}

static int get_index_from_var(WasmBindingVector* bindings, WasmVar* var) {
  if (var->type == WASM_VAR_TYPE_NAME)
    return find_binding_index_by_name(bindings, &var->name);
  return var->index;
}

#define DEFINE_GET_ITEM_BY_NAME(NAME, TYPE)                          \
  static TYPE##Ptr get_##NAME##_by_name(WasmBindingVector* bindings, \
                                        TYPE##PtrVector* items,      \
                                        WasmStringSlice* name) {     \
    int index = find_binding_index_by_name(bindings, name);          \
    if (index == -1)                                                 \
      return NULL;                                                   \
    return items->data[index];                                       \
  }
DEFINE_GET_ITEM_BY_NAME(func, WasmFunc)
DEFINE_GET_ITEM_BY_NAME(func_type, WasmFuncType)
DEFINE_GET_ITEM_BY_NAME(export, WasmExport)

#define DEFINE_GET_ITEM_BY_VAR(NAME, TYPE)                                     \
  static TYPE##Ptr get_##NAME##_by_var(WasmBindingVector* bindings,            \
                                       TYPE##PtrVector* items, WasmVar* var) { \
    int index = get_index_from_var(bindings, var);                             \
    if (index < 0 || index >= items->size)                                     \
      return NULL;                                                             \
    return items->data[index];                                                 \
  }
DEFINE_GET_ITEM_BY_VAR(func, WasmFunc)
DEFINE_GET_ITEM_BY_VAR(func_type, WasmFuncType)

static WasmResult check_duplicate_bindings(WasmCheckContext* ctx,
                                           WasmBindingVector* bindings,
                                           const char* desc) {
  int i, j;
  WasmResult result = WASM_OK;
  for (i = 1; i < bindings->size; ++i) {
    WasmBinding* ib = &bindings->data[i];
    for (j = 0; j < i; ++j) {
      WasmBinding* jb = &bindings->data[j];
      if (string_slices_are_equal(&ib->name, &jb->name)) {
        print_error(ctx, &ib->loc, "redefinition of %s \"%.*s\"", desc,
                    ib->name.length, ib->name.start);
        result = WASM_ERROR;
      }
    }
  }
  return result;
}

static WasmResult check_var(WasmCheckContext* ctx,
                            WasmBindingVector* bindings,
                            int max_index,
                            WasmVar* var,
                            const char* desc,
                            int* out_index) {
  int index = get_index_from_var(bindings, var);
  if (index >= 0 && index < max_index) {
    if (out_index)
      *out_index = index;
    return WASM_OK;
  }
  if (var->type == WASM_VAR_TYPE_NAME)
    print_error(ctx, &var->loc, "undefined %s variable \"%.*s\"", desc,
                var->name.length, var->name.start);
  else
    print_error(ctx, &var->loc, "%s variable out of range (max %d)", desc,
                max_index);
  return WASM_ERROR;
}

static WasmResult check_func_var(WasmCheckContext* ctx,
                                 WasmModule* module,
                                 WasmVar* var,
                                 WasmFunc** out_func) {
  int index;
  if (check_var(ctx, &module->func_bindings, module->funcs.size, var,
                "function", &index) != WASM_OK)
    return WASM_ERROR;

  if (out_func)
    *out_func = module->funcs.data[index];
  return WASM_OK;
}

static WasmResult check_import_var(WasmCheckContext* ctx,
                                   WasmModule* module,
                                   WasmVar* var,
                                   WasmImport** out_import) {
  int index;
  if (check_var(ctx, &module->import_bindings, module->imports.size, var,
                "import", &index) != WASM_OK)
    return WASM_ERROR;

  if (out_import)
    *out_import = module->imports.data[index];
  return WASM_OK;
}

static WasmResult check_func_type_var(WasmCheckContext* ctx,
                                      WasmModule* module,
                                      WasmVar* var,
                                      WasmFuncType** out_func_type) {
  int index;
  if (check_var(ctx, &module->func_type_bindings, module->func_types.size, var,
                "function type", &index) != WASM_OK)
    return WASM_ERROR;

  if (out_func_type)
    *out_func_type = module->func_types.data[index];
  return WASM_OK;
}

static WasmResult check_local_var(WasmCheckContext* ctx,
                                  WasmFunc* func,
                                  WasmVar* var,
                                  WasmType* out_type) {
  int index;
  if (check_var(ctx, &func->params_and_locals.bindings,
                func->params_and_locals.types.size, var, "local",
                &index) != WASM_OK)
    return WASM_ERROR;

  if (out_type)
    *out_type = func->params_and_locals.types.data[index];
  return WASM_OK;
}

static WasmResult check_global_var(WasmCheckContext* ctx,
                                   WasmModule* module,
                                   WasmVar* var,
                                   WasmType* out_type) {
  int index;
  if (check_var(ctx, &module->globals.bindings, module->globals.types.size, var,
                "global", &index) != WASM_OK)
    return WASM_ERROR;

  if (out_type)
    *out_type = module->globals.types.data[index];
  return WASM_OK;
}

static WasmResult check_type(WasmCheckContext* ctx,
                             WasmLocation* loc,
                             WasmType actual,
                             WasmType expected,
                             const char* desc) {
  if (expected != WASM_TYPE_VOID && (actual & expected) == 0) {
    print_error(ctx, loc, "type mismatch%s. got %s, expected %s", desc,
                s_type_names[actual], s_type_names[expected]);
    return WASM_ERROR;
  }
  return WASM_OK;
}

static WasmResult check_type_exact(WasmCheckContext* ctx,
                                   WasmLocation* loc,
                                   WasmType actual,
                                   WasmType expected,
                                   const char* desc) {
  if (actual != expected) {
    print_error(ctx, loc, "type mismatch%s. got %s, expected %s", desc,
                s_type_names[actual], s_type_names[expected]);
    return WASM_ERROR;
  }
  return WASM_OK;
}

static WasmResult check_type_arg_exact(WasmCheckContext* ctx,
                                       WasmLocation* loc,
                                       WasmType actual,
                                       WasmType expected,
                                       const char* desc,
                                       int arg_index) {
  if (actual != expected) {
    print_error(ctx, loc,
                "type mismatch for argument %d of %s. got %s, expected %s",
                arg_index, desc, s_type_names[actual], s_type_names[expected]);
    return WASM_ERROR;
  }
  return WASM_OK;
}

static WasmLabelNode* find_label_by_name(WasmLabelNode* top_label,
                                         WasmStringSlice* name) {
  WasmLabelNode* node = top_label;
  while (node) {
    if (node->label && string_slices_are_equal(node->label, name))
      return node;
    node = node->next;
  }
}

static WasmLabelNode* find_label_by_var(WasmLabelNode* top_label,
                                        WasmVar* var) {
  if (var->type == WASM_VAR_TYPE_NAME)
    return find_label_by_name(top_label, &var->name);

  WasmLabelNode* node = top_label;
  int i = 0;
  while (node && i != var->index) {
    node = node->next;
    i++;
  }
  return node;
}

static WasmResult check_label_var(WasmCheckContext* ctx,
                                  WasmLabelNode* top_label,
                                  WasmVar* var,
                                  WasmLabelNode** out_node) {
  WasmLabelNode* node = find_label_by_var(top_label, var);
  if (node) {
    if (out_node)
      *out_node = node;
    return WASM_OK;
  }
  if (var->type == WASM_VAR_TYPE_NAME)
    print_error(ctx, &var->loc, "undefined label variable \"%.*s\"",
                var->name.length, var->name.start);
  else
    print_error(ctx, &var->loc, "label variable out of range (max %d)",
                top_label ? top_label->depth + 1 : 0);
  return WASM_ERROR;
}

static WasmResult push_label(WasmCheckContext* ctx,
                             WasmLocation* loc,
                             WasmLabelNode* node,
                             WasmLabel* label,
                             WasmType expected_type,
                             const char* desc) {
  WasmResult result = WASM_OK;
  if (label && find_label_by_name(ctx->top_label, label)) {
    print_error(ctx, loc, "redefinition of label \"%.*s\"", label->length,
                label->start);
    /* add it anyway */
    result = WASM_ERROR;
  }
  node->label = label;
  node->next = ctx->top_label;
  node->depth = ctx->top_label ? ctx->top_label->depth + 1 : 0;
  node->expected_type = expected_type;
  node->desc = desc;
  ctx->top_label = node;
  return result;
}

static void pop_label(WasmCheckContext* ctx) {
  ctx->top_label = ctx->top_label->next;
}

static WasmResult check_expr(WasmCheckContext* ctx,
                             WasmModule* module,
                             WasmFunc* func,
                             WasmExpr* expr,
                             WasmType expected_type,
                             const char* desc);

static WasmResult check_call(WasmCheckContext* ctx,
                             WasmLocation* loc,
                             WasmModule* module,
                             WasmFunc* func,
                             WasmTypeVector* param_types,
                             WasmType result_type,
                             WasmExprPtrVector* args,
                             WasmType expected_type,
                             const char* desc) {
  WasmResult result = WASM_OK;
  int actual_args = args->size;
  int expected_args = param_types->size;
  if (expected_args == actual_args) {
    result |= check_type(ctx, loc, result_type, expected_type, "");
    char buffer[100];
    int i;
    for (i = 0; i < actual_args; ++i) {
      snprintf(buffer, 100, " of argument %d of %s", i, desc);
      result |= check_expr(ctx, module, func, args->data[i],
                           param_types->data[i], buffer);
    }
  } else {
    print_error(ctx, loc, "too %s parameters to function. got %d, expected %d",
                actual_args > expected_args ? "many" : "few", actual_args,
                expected_args);
    result = WASM_ERROR;
  }
  return result;
}

static WasmResult check_target(WasmCheckContext* ctx,
                               WasmBindingVector* bindings,
                               int num_cases,
                               WasmTarget* target) {
  switch (target->type) {
    case WASM_TARGET_TYPE_CASE:
      return check_var(ctx, bindings, num_cases, &target->var, "case", NULL);
    case WASM_TARGET_TYPE_BR:
      return check_label_var(ctx, ctx->top_label, &target->var, NULL);
    default:
      return WASM_ERROR;
  }
}

static WasmResult check_exprs(WasmCheckContext* ctx,
                              WasmModule* module,
                              WasmFunc* func,
                              WasmExprPtrVector* exprs,
                              WasmType expected_type,
                              const char* desc) {
  WasmResult result = WASM_OK;
  if (exprs->size > 0) {
    int i;
    WasmExprPtr* expr = &exprs->data[0];
    for (i = 0; i < exprs->size - 1; ++i, ++expr)
      result |= check_expr(ctx, module, func, *expr, WASM_TYPE_VOID, "");
    result |= check_expr(ctx, module, func, *expr, expected_type, desc);
  }
  return result;
}

static WasmResult check_expr(WasmCheckContext* ctx,
                             WasmModule* module,
                             WasmFunc* func,
                             WasmExpr* expr,
                             WasmType expected_type,
                             const char* desc) {
  WasmResult result = WASM_OK;
  switch (expr->type) {
    case WASM_EXPR_TYPE_BINARY: {
      WasmType type = expr->binary.op.type;
      result |= check_type(ctx, &expr->loc, type, expected_type, desc);
      result |= check_expr(ctx, module, func, expr->binary.left, type,
                           " of argument 0 of binary op");
      result |= check_expr(ctx, module, func, expr->binary.right, type,
                           " of argument 1 of binary op");
      break;
    }
    case WASM_EXPR_TYPE_BLOCK: {
      int has_label = expr->block.label.start != NULL;
      WasmLabelNode node;
      if (has_label)
        push_label(ctx, &expr->loc, &node, &expr->block.label, expected_type,
                   "block");
      result |= check_exprs(ctx, module, func, &expr->block.exprs,
                            expected_type, " of block");
      if (has_label)
        pop_label(ctx);
      break;
    }
    case WASM_EXPR_TYPE_BR: {
      WasmLabelNode* node;
      if (check_label_var(ctx, ctx->top_label, &expr->br.var, &node) ==
          WASM_OK) {
        if (expr->br.expr) {
          result |= check_expr(ctx, module, func, expr->br.expr,
                               node->expected_type, " of br value");
        } else {
          char buffer[100];
          snprintf(buffer, 100, " of %s", node->desc);
          result |= check_type(ctx, &expr->loc, WASM_TYPE_VOID,
                               node->expected_type, buffer);
        }
      } else {
        result = WASM_ERROR;
      }
      break;
    }
    case WASM_EXPR_TYPE_BR_IF:
      result |= check_expr(ctx, module, func, expr->br_if.cond, WASM_TYPE_I32,
                           " of br_if condition");
      result |= check_label_var(ctx, ctx->top_label, &expr->br_if.var, NULL);
      break;
    case WASM_EXPR_TYPE_CALL: {
      WasmFunc* func;
      if (check_func_var(ctx, module, &expr->call.var, &func) == WASM_OK) {
        result |= check_call(ctx, &expr->loc, module, func, &func->params.types,
                             func->result_type, &expr->call.args, expected_type,
                             "call");
      } else {
        result = WASM_ERROR;
      }
      break;
    }
    case WASM_EXPR_TYPE_CALL_IMPORT: {
      WasmImport* import;
      if (check_import_var(ctx, module, &expr->call.var, &import) == WASM_OK) {
        WasmFuncSignature* sig = NULL;
        if (import->import_type == WASM_IMPORT_HAS_TYPE) {
          WasmFuncType* func_type;
          if (check_func_type_var(ctx, module, &import->type_var, &func_type) ==
              WASM_OK) {
            sig = &func_type->sig;
          } else {
            result = WASM_ERROR;
          }
        } else {
          assert(import->import_type == WASM_IMPORT_HAS_FUNC_SIGNATURE);
          sig = &import->func_sig;
        }
        if (sig) {
          result |= check_call(ctx, &expr->loc, module, func, &sig->param_types,
                               sig->result_type, &expr->call.args,
                               expected_type, "call_import");
        }
      } else {
        result = WASM_ERROR;
      }
      break;
    }
    case WASM_EXPR_TYPE_CALL_INDIRECT: {
      result |= check_expr(ctx, module, func, expr->call_indirect.expr,
                           WASM_TYPE_I32, " of function index");
      WasmFuncType* func_type;
      if (check_func_type_var(ctx, module, &expr->call_indirect.var,
                              &func_type) == WASM_OK) {
        WasmFuncSignature* sig = &func_type->sig;
        result |= check_call(ctx, &expr->loc, module, func, &sig->param_types,
                             sig->result_type, &expr->call_indirect.args,
                             expected_type, "call_indirect");
      } else {
        result = WASM_ERROR;
      }
      break;
    }
    case WASM_EXPR_TYPE_CAST: {
      WasmType type = expr->cast.op.type;
      result |= check_type(ctx, &expr->loc, type, expected_type, desc);
      result |= check_expr(ctx, module, func, expr->cast.expr,
                           expr->cast.op.type2, " of cast op");
      break;
    }
    case WASM_EXPR_TYPE_COMPARE: {
      WasmType type = expr->convert.op.type;
      result |= check_type(ctx, &expr->loc, type, expected_type, desc);
      result |= check_expr(ctx, module, func, expr->compare.left, type,
                           " of argument 0 of compare op");
      result |= check_expr(ctx, module, func, expr->compare.right, type,
                           " of argument 1 of compare op");
      break;
    }
    case WASM_EXPR_TYPE_CONST:
      result |=
          check_type(ctx, &expr->loc, expr->const_.type, expected_type, desc);
      break;
    case WASM_EXPR_TYPE_CONVERT: {
      result |= check_type(ctx, &expr->loc, expr->convert.op.type,
                           expected_type, desc);
      result |= check_expr(ctx, module, func, expr->convert.expr,
                           expr->convert.op.type2, " of convert op");
      break;
    }
    case WASM_EXPR_TYPE_GET_LOCAL: {
      WasmType type;
      if (check_local_var(ctx, func, &expr->get_local.var, &type) == WASM_OK)
        result |= check_type(ctx, &expr->loc, type, expected_type, desc);
      else
        result = WASM_ERROR;
      break;
    }
    case WASM_EXPR_TYPE_GROW_MEMORY:
      result |= check_expr(ctx, module, func, expr->grow_memory.expr,
                           WASM_TYPE_I32, " of grow_memory");
      break;
    case WASM_EXPR_TYPE_HAS_FEATURE:
      result |= check_type(ctx, &expr->loc, WASM_TYPE_I32, expected_type,
                           " in has_feature");
      break;
    case WASM_EXPR_TYPE_IF:
      result |= check_expr(ctx, module, func, expr->if_.cond, WASM_TYPE_I32,
                           " of condition");
      result |= check_expr(ctx, module, func, expr->if_.true_, expected_type,
                           " of if branch");
      result |=
          check_type(ctx, &expr->loc, WASM_TYPE_VOID, expected_type, desc);
      break;
    case WASM_EXPR_TYPE_IF_ELSE:
      result |= check_expr(ctx, module, func, expr->if_else.cond, WASM_TYPE_I32,
                           " of condition");
      result |= check_expr(ctx, module, func, expr->if_else.true_,
                           expected_type, " of if branch");
      result |= check_expr(ctx, module, func, expr->if_else.false_,
                           expected_type, " of if branch");
      break;
    case WASM_EXPR_TYPE_LABEL: {
      WasmLabelNode node;
      push_label(ctx, &expr->loc, &node, &expr->label.label, expected_type,
                 "label");
      result |= check_expr(ctx, module, func, expr->label.expr, expected_type,
                           " of label");
      pop_label(ctx);
      break;
    }
    case WASM_EXPR_TYPE_LOAD: {
      WasmType type = expr->load.op.type;
      result |= check_type(ctx, &expr->loc, type, expected_type, desc);
      result |= check_expr(ctx, module, func, expr->load.addr, WASM_TYPE_I32,
                           " of load index");
      break;
    }
    case WASM_EXPR_TYPE_LOAD_EXTEND: {
      WasmType type = expr->load.op.type;
      result |= check_type(ctx, &expr->loc, type, expected_type, desc);
      result |= check_expr(ctx, module, func, expr->load.addr, WASM_TYPE_I32,
                           " of load index");
      break;
    }
    case WASM_EXPR_TYPE_LOAD_GLOBAL: {
      WasmType type;
      if (check_global_var(ctx, module, &expr->load_global.var, &type) ==
          WASM_OK)
        result |= check_type(ctx, &expr->loc, type, expected_type, desc);
      else
        result = WASM_ERROR;
      break;
    }
    case WASM_EXPR_TYPE_LOOP: {
      WasmLabelNode outer_node;
      push_label(ctx, &expr->loc, &outer_node, &expr->loop.outer, expected_type,
                 "loop outer label");
      int has_inner_label = expr->loop.inner.start != NULL;
      if (has_inner_label) {
        WasmLabelNode inner_node;
        push_label(ctx, &expr->loc, &inner_node, &expr->loop.inner,
                   WASM_TYPE_VOID, "loop inner label");
      }
      result |= check_exprs(ctx, module, func, &expr->loop.exprs, expected_type,
                            " of loop");
      if (has_inner_label)
        pop_label(ctx);
      pop_label(ctx);
      break;
    }
    case WASM_EXPR_TYPE_MEMORY_SIZE:
      result |= check_type(ctx, &expr->loc, WASM_TYPE_I32, expected_type,
                           " in memory_size");
      break;
    case WASM_EXPR_TYPE_NOP:
      result |=
          check_type(ctx, &expr->loc, WASM_TYPE_VOID, expected_type, " in nop");
      break;
    case WASM_EXPR_TYPE_PAGE_SIZE:
      result |= check_type(ctx, &expr->loc, WASM_TYPE_I32, expected_type,
                           " in page_size");
      break;
    case WASM_EXPR_TYPE_RETURN:
      if (expr->return_.expr) {
        result |= check_expr(ctx, module, func, expr->return_.expr,
                             func->result_type, " of return");
      } else {
        result |= check_type(ctx, &expr->loc, WASM_TYPE_VOID, func->result_type,
                             desc);
      }
      break;
    case WASM_EXPR_TYPE_SELECT:
      result |=
          check_type(ctx, &expr->loc, expr->select.type, expected_type, desc);
      result |= check_expr(ctx, module, func, expr->select.cond, WASM_TYPE_I32,
                           " of condition");
      result |= check_expr(ctx, module, func, expr->select.true_,
                           expr->select.type, " of argument 0 of select op");
      result |= check_expr(ctx, module, func, expr->select.false_,
                           expr->select.type, " of argment 1 of select op");
      break;
    case WASM_EXPR_TYPE_SET_LOCAL: {
      WasmType type;
      if (check_local_var(ctx, func, &expr->set_local.var, &type) == WASM_OK) {
        result |= check_type(ctx, &expr->loc, type, expected_type, desc);
        result |= check_expr(ctx, module, func, expr->set_local.expr, type,
                             " of set_local");
      } else {
        result = WASM_ERROR;
      }
      break;
    }
    case WASM_EXPR_TYPE_STORE: {
      WasmType type = expr->store.op.type;
      result |= check_type(ctx, &expr->loc, type, expected_type, desc);
      result |= check_expr(ctx, module, func, expr->store.addr, WASM_TYPE_I32,
                           " of store index");
      result |= check_expr(ctx, module, func, expr->store.value, type,
                           " of store value");
      break;
    }
    case WASM_EXPR_TYPE_STORE_GLOBAL: {
      WasmType type;
      if (check_global_var(ctx, module, &expr->store_global.var, &type) ==
          WASM_OK) {
        result |= check_type(ctx, &expr->loc, type, expected_type, desc);
        result |= check_expr(ctx, module, func, expr->store_global.expr, type,
                             " of store_global");
      } else {
        result = WASM_ERROR;
      }
      break;
    }
    case WASM_EXPR_TYPE_STORE_WRAP: {
      WasmType type = expr->store.op.type;
      result |= check_type(ctx, &expr->loc, type, expected_type, desc);
      result |= check_expr(ctx, module, func, expr->store.addr, WASM_TYPE_I32,
                           " of store index");
      result |= check_expr(ctx, module, func, expr->store.value, type,
                           " of store value");
      break;
    }
    case WASM_EXPR_TYPE_TABLESWITCH: {
      result |= check_duplicate_bindings(ctx, &expr->tableswitch.case_bindings,
                                         "case");

      WasmLabelNode node;
      int has_label = expr->tableswitch.label.start != NULL;
      if (has_label)
        push_label(ctx, &expr->loc, &node, &expr->tableswitch.label,
                   expected_type, "tableswitch");
      result |= check_expr(ctx, module, func, expr->tableswitch.expr,
                           WASM_TYPE_I32, " of key");
      int i;
      for (i = 0; i < expr->tableswitch.targets.size; ++i) {
        WasmTarget* target = &expr->tableswitch.targets.data[i];
        result |= check_target(ctx, &expr->tableswitch.case_bindings,
                               expr->tableswitch.cases.size, target);
      }
      result |= check_target(ctx, &expr->tableswitch.case_bindings,
                             expr->tableswitch.cases.size,
                             &expr->tableswitch.default_target);
      int num_cases = expr->tableswitch.cases.size;
      if (num_cases > 0) {
        WasmCase* case_ = &expr->tableswitch.cases.data[0];
        for (i = 0; i < num_cases - 1; ++i, ++case_) {
          result |=
              check_exprs(ctx, module, func, &case_->exprs, WASM_TYPE_VOID, "");
        }
        result |= check_exprs(ctx, module, func, &case_->exprs, expected_type,
                              " of tableswitch case");
      }
      if (has_label)
        pop_label(ctx);
      break;
    }
    case WASM_EXPR_TYPE_UNARY: {
      WasmType type = expr->unary.op.type;
      result |= check_type(ctx, &expr->loc, type, expected_type, desc);
      result |= check_expr(ctx, module, func, expr->unary.expr,
                           expr->unary.op.type, " of unary op");
      break;
    }
    case WASM_EXPR_TYPE_UNREACHABLE:
      break;
  }
  return result;
}

static WasmResult check_func(WasmCheckContext* ctx,
                             WasmModule* module,
                             WasmLocation* loc,
                             WasmFunc* func) {
  WasmResult result = WASM_OK;
  if (func->flags & WASM_FUNC_FLAG_HAS_FUNC_TYPE) {
    WasmFuncType* func_type;
    if (check_func_type_var(ctx, module, &func->type_var, &func_type) ==
        WASM_OK) {
      if (func->flags & WASM_FUNC_FLAG_HAS_SIGNATURE) {
        result |= check_type_exact(ctx, &func->loc, func->result_type,
                                   func_type->sig.result_type, "");
        if (func->params.types.size == func_type->sig.param_types.size) {
          int i;
          for (i = 0; i < func->params.types.size; ++i) {
            result |= check_type_arg_exact(
                ctx, &func->loc, func->params.types.data[i],
                func_type->sig.param_types.data[i], "function", i);
          }
        } else {
          print_error(ctx, &func->loc, "expected %d parameters, got %d",
                      func_type->sig.param_types.size, func->params.types.size);
          result = WASM_ERROR;
        }
      }
    } else {
      result = WASM_ERROR;
    }
  }

  result |= check_duplicate_bindings(ctx, &func->params.bindings, "parameter");
  result |= check_duplicate_bindings(ctx, &func->locals.bindings, "local");
  result |= check_exprs(ctx, module, func, &func->exprs, func->result_type,
                        " of function result");
  return result;
}

static WasmResult check_import(WasmCheckContext* ctx,
                               WasmModule* module,
                               WasmLocation* loc,
                               WasmImport* import) {
  if (import->import_type != WASM_IMPORT_HAS_TYPE)
    return WASM_OK;

  return check_import_var(ctx, module, &import->type_var, NULL);
}

static WasmResult check_export(WasmCheckContext* ctx,
                               WasmModule* module,
                               WasmExport* export) {
  return check_func_var(ctx, module, &export->var, NULL);
}

static WasmResult check_table(WasmCheckContext* ctx,
                              WasmModule* module,
                              WasmVarVector* table) {
  WasmResult result = WASM_OK;
  int i;
  for (i = 0; i < table->size; ++i)
    result |= check_func_var(ctx, module, &table->data[i], NULL);
  return result;
}

static WasmResult check_memory(WasmCheckContext* ctx,
                               WasmModule* module,
                               WasmMemory* memory) {
  WasmResult result = WASM_OK;
  if (memory->max_size < memory->initial_size) {
    print_error(
        ctx, &memory->loc,
        "max size (%u) must be greater than or equal to initial size (%u)",
        memory->max_size, memory->initial_size);
    result = WASM_ERROR;
  }
  int i;
  uint32_t last_end = 0;
  for (i = 0; i < memory->segments.size; ++i) {
    WasmSegment* segment = &memory->segments.data[i];
    if (segment->addr < last_end) {
      print_error(ctx, &segment->loc,
                  "address (%u) less than end of previous segment (%u)",
                  segment->addr, last_end);
      result = WASM_ERROR;
    }
    if (segment->addr >= memory->initial_size) {
      print_error(ctx, &segment->loc,
                  "address (%u) greater than initial memory size (%u)",
                  segment->addr, memory->initial_size);
      result = WASM_ERROR;
    } else if (segment->addr + segment->size >= memory->initial_size) {
      print_error(ctx, &segment->loc,
                  "segment ends past the end of initial memory size (%u)",
                  memory->initial_size);
      result = WASM_ERROR;
    }
    last_end = segment->addr + segment->size;
  }
  return result;
}

static WasmResult check_module(WasmCheckContext* ctx, WasmModule* module) {
  WasmResult result = WASM_OK;
  int i;
  int seen_memory = 0;
  int seen_table = 0;
  for (i = 0; i < module->fields.size; ++i) {
    WasmModuleField* field = &module->fields.data[i];
    switch (field->type) {
      case WASM_MODULE_FIELD_TYPE_FUNC:
        result |= check_func(ctx, module, &field->loc, &field->func);
        break;
      case WASM_MODULE_FIELD_TYPE_IMPORT:
        result |= check_import(ctx, module, &field->loc, &field->import);
        break;
      case WASM_MODULE_FIELD_TYPE_EXPORT:
        result |= check_export(ctx, module, &field->export);
        break;
      case WASM_MODULE_FIELD_TYPE_TABLE:
        if (seen_table) {
          print_error(ctx, &field->loc, "only one table allowed");
          result |= WASM_ERROR;
        }
        result |= check_table(ctx, module, &field->table);
        seen_table = 1;
        break;
      case WASM_MODULE_FIELD_TYPE_MEMORY:
        if (seen_memory) {
          print_error(ctx, &field->loc, "only one memory block allowed");
          result |= WASM_ERROR;
        }
        result |= check_memory(ctx, module, &field->memory);
        seen_memory = 1;
        break;

      case WASM_MODULE_FIELD_TYPE_FUNC_TYPE:
      case WASM_MODULE_FIELD_TYPE_GLOBAL:
        break;
    }
  }

  result |= check_duplicate_bindings(ctx, &module->func_bindings, "function");
  result |= check_duplicate_bindings(ctx, &module->import_bindings, "import");
  result |= check_duplicate_bindings(ctx, &module->export_bindings, "export");
  result |= check_duplicate_bindings(ctx, &module->func_type_bindings,
                                     "function type");
  result |= check_duplicate_bindings(ctx, &module->globals.bindings, "global");

  return result;
}

static WasmResult check_invoke(WasmCheckContext* ctx,
                               WasmCommandInvoke* invoke,
                               WasmType return_type) {
  if (!ctx->last_module) {
    print_error(ctx, &invoke->loc,
                "invoke must occur after a module definition");
    return WASM_ERROR;
  }

  WasmExport* export =
      get_export_by_name(&ctx->last_module->export_bindings,
                         &ctx->last_module->exports, &invoke->name);
  if (!export) {
    print_error(ctx, &invoke->loc, "unknown function export \"%.*s\"",
                invoke->name.length, invoke->name.start);
    return WASM_ERROR;
  }

  WasmFunc* func = get_func_by_var(&ctx->last_module->func_bindings,
                                   &ctx->last_module->funcs, &export->var);
  if (!func) {
    /* this error will have already been reported, just skip it */
    return WASM_ERROR;
  }

  int actual_args = invoke->args.size;
  int expected_args = func->params.types.size;
  if (expected_args != actual_args) {
    print_error(ctx, &invoke->loc,
                "too %s parameters to function. got %d, expected %d",
                actual_args > expected_args ? "many" : "few", actual_args,
                expected_args);
    return WASM_ERROR;
  }
  WasmResult result =
      check_type(ctx, &invoke->loc, func->result_type, return_type, "");
  int i;
  for (i = 0; i < actual_args; ++i) {
    WasmConst* const_ = &invoke->args.data[i];
    result |= check_type_arg_exact(ctx, &const_->loc, const_->type,
                                   func->params.types.data[i], "invoke", i);
  }
  return result;
}

static WasmResult check_command(WasmCheckContext* ctx, WasmCommand* command) {
  switch (command->type) {
    case WASM_COMMAND_TYPE_MODULE:
      ctx->last_module = &command->module;
      return check_module(ctx, &command->module);
    case WASM_COMMAND_TYPE_INVOKE:
      return check_invoke(ctx, &command->invoke, WASM_TYPE_VOID);
    case WASM_COMMAND_TYPE_ASSERT_INVALID: {
      ctx->in_assert_invalid = 1;
      WasmResult module_ok = check_module(ctx, &command->assert_invalid.module);
      ctx->in_assert_invalid = 0;
      if (module_ok == WASM_OK) {
        /* error, module should be invalid */
        print_error(ctx, &command->assert_invalid.module.loc,
                    "expected module to be invalid");
        return WASM_ERROR;
      }
      return WASM_OK;
    }
    case WASM_COMMAND_TYPE_ASSERT_RETURN:
      return check_invoke(ctx, &command->assert_return.invoke,
                          command->assert_return.expected.type);
    case WASM_COMMAND_TYPE_ASSERT_RETURN_NAN:
      return check_invoke(ctx, &command->assert_return_nan.invoke,
                          WASM_TYPE_F32 | WASM_TYPE_F64);
    case WASM_COMMAND_TYPE_ASSERT_TRAP:
      return check_invoke(ctx, &command->assert_trap.invoke, WASM_TYPE_VOID);
  }
}

WasmResult wasm_check_script(WasmScript* script) {
  WasmCheckContext ctx = {};
  WasmResult result = WASM_OK;
  int i;
  for (i = 0; i < script->commands.size; ++i)
    result |= check_command(&ctx, &script->commands.data[i]);
  return result;
}