[wasm] Change the constant kV8MaxWasmMemoryPages to a command line flag.

src/flags.cc

Index: src/flags.cc
diff --git a/src/flags.cc b/src/flags.cc
index f7ae004ac26e2bf7e80583b0c4e87b19fdddb5ca..07a31c38fe35c05ed1b5d0b7977002f709d1abae 100644
--- a/src/flags.cc
+++ b/src/flags.cc
@@ -33,8 +33,15 @@ namespace {
 // to the actual flag, default value, comment, etc.  This is designed to be POD
 // initialized as to avoid requiring static constructors.
 struct Flag {
-  enum FlagType { TYPE_BOOL, TYPE_MAYBE_BOOL, TYPE_INT, TYPE_FLOAT,
-                  TYPE_STRING, TYPE_ARGS };
+  enum FlagType {
+    TYPE_BOOL,
+    TYPE_MAYBE_BOOL,
+    TYPE_INT,
+    TYPE_UINT,
+    TYPE_FLOAT,
+    TYPE_STRING,
+    TYPE_ARGS
+  };
 
   FlagType type_;           // What type of flag, bool, int, or string.
   const char* name_;        // Name of the flag, ex "my_flag".
@@ -64,6 +71,11 @@ struct Flag {
     return reinterpret_cast<int*>(valptr_);
   }
 
+  unsigned int* uint_variable() const {
+    DCHECK(type_ == TYPE_UINT);
+    return reinterpret_cast<unsigned int*>(valptr_);
+  }
+
   double* float_variable() const {
     DCHECK(type_ == TYPE_FLOAT);
     return reinterpret_cast<double*>(valptr_);
@@ -97,6 +109,11 @@ struct Flag {
     return *reinterpret_cast<const int*>(defptr_);
   }
 
+  unsigned int uint_default() const {
+    DCHECK(type_ == TYPE_UINT);
+    return *reinterpret_cast<const unsigned int*>(defptr_);
+  }
+
   double float_default() const {
     DCHECK(type_ == TYPE_FLOAT);
     return *reinterpret_cast<const double*>(defptr_);
@@ -121,6 +138,8 @@ struct Flag {
         return maybe_bool_variable()->has_value == false;
       case TYPE_INT:
         return *int_variable() == int_default();
+      case TYPE_UINT:
+        return *uint_variable() == uint_default();
       case TYPE_FLOAT:
         return *float_variable() == float_default();
       case TYPE_STRING: {
@@ -149,6 +168,9 @@ struct Flag {
       case TYPE_INT:
         *int_variable() = int_default();
         break;
+      case TYPE_UINT:
+        *uint_variable() = uint_default();
+        break;
       case TYPE_FLOAT:
         *float_variable() = float_default();
         break;
@@ -177,6 +199,8 @@ static const char* Type2String(Flag::FlagType type) {
     case Flag::TYPE_BOOL: return "bool";
     case Flag::TYPE_MAYBE_BOOL: return "maybe_bool";
     case Flag::TYPE_INT: return "int";
+    case Flag::TYPE_UINT:
+      return "uint";
     case Flag::TYPE_FLOAT: return "float";
     case Flag::TYPE_STRING: return "string";
     case Flag::TYPE_ARGS: return "arguments";
@@ -199,6 +223,9 @@ std::ostream& operator<<(std::ostream& os, const Flag& flag) {  // NOLINT
     case Flag::TYPE_INT:
       os << *flag.int_variable();
       break;
+    case Flag::TYPE_UINT:
+      os << *flag.uint_variable();
+      break;
     case Flag::TYPE_FLOAT:
       os << *flag.float_variable();
       break;
@@ -399,6 +426,24 @@ int FlagList::SetFlagsFromCommandLine(int* argc,
         case Flag::TYPE_INT:
           *flag->int_variable() = static_cast<int>(strtol(value, &endp, 10));
           break;
+        case Flag::TYPE_UINT: {
+          // We do not use strtoul because it accepts negative numbers.
+          int64_t val = static_cast<int64_t>(strtoll(value, &endp, 10));
+          if (val < 0 || val > std::numeric_limits<unsigned int>::max()) {
+            PrintF(stderr,
+                   "Error: Value for flag %s of type %s is out of bounds "
+                   "[0-%" PRIu64
+                   "]\n"
+                   "Try --help for options\n",
+                   arg, Type2String(flag->type()),
+                   static_cast<uint64_t>(
+                       std::numeric_limits<unsigned int>::max()));
+            return_code = j;
+            break;
+          }
+          *flag->uint_variable() = static_cast<unsigned int>(val);
+          break;
+        }
         case Flag::TYPE_FLOAT:
           *flag->float_variable() = strtod(value, &endp);
           break;