Move bytecode version constant to its own header

Summary:
Add a header file that only contains the bytecode version number.

This makes it easier to programmatically determine whether
the version has been updated, enabling greater signal-to-noise
ratio in tooling that prevents forgotten version bumps.

Reviewed By: neildhar

Differential Revision: D29522296

fbshipit-source-id: 13cdd668b53bafec3049cc19181b334ace9d2ca3

include/hermes/BCGen/HBC/BytecodeFileFormat.h

@@ -8,6 +8,7 @@
 #ifndef HERMES_BCGEN_HBC_BYTECODEFILEFORMAT_H
 #define HERMES_BCGEN_HBC_BYTECODEFILEFORMAT_H
 
+#include "hermes/BCGen/HBC/BytecodeVersion.h"
 #include "hermes/BCGen/HBC/StringKind.h"
 #include "hermes/Support/Compiler.h"
 #include "hermes/Support/RegExpSerialization.h"
@@ -28,10 +29,6 @@ const static uint64_t MAGIC = 0x1F1903C103BC1FC6;
 // bytecode file is in a form suitable for delta diffing, not execution.
 const static uint64_t DELTA_MAGIC = ~MAGIC;
 
-// Bytecode version generated by this version of the compiler.
-// Updated: Mar 11, 2021
-const static uint32_t BYTECODE_VERSION = 83;
-
 /// Property cache index which indicates no caching.
 static constexpr uint8_t PROPERTY_CACHING_DISABLED = 0;
 

include/hermes/BCGen/HBC/BytecodeVersion.h

@@ -0,0 +1,28 @@
+/*
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#ifndef HERMES_BCGEN_HBC_BYTECODEVERSION_H
+#define HERMES_BCGEN_HBC_BYTECODEVERSION_H
+
+#include <cstdint>
+
+/*
+ * This file should *only* contain the version number constant definition,
+ * to enable tooling to determine whether the version has been updated.
+ */
+
+namespace hermes {
+namespace hbc {
+
+// Bytecode version generated by this version of the compiler.
+// Updated: Mar 11, 2021
+const static uint32_t BYTECODE_VERSION = 83;
+
+} // namespace hbc
+} // namespace hermes
+
+#endif // HERMES_BCGEN_HBC_BYTECODEVERSION_H