Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 92 insertions, 0 deletions

diff --git a/js/src/util/CheckedArithmetic.h b/js/src/util/CheckedArithmetic.h
new file mode 100644
index 0000000000..4bab3f440a
--- /dev/null
+++ b/js/src/util/CheckedArithmetic.h
@@ -0,0 +1,92 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef util_CheckedArithmetic_h
+#define util_CheckedArithmetic_h
+
+#include "mozilla/Compiler.h"
+#include "mozilla/MathAlgorithms.h"
+
+#include <stdint.h>
+
+// This macro is should be `one' if current compiler supports builtin functions
+// like __builtin_sadd_overflow.
+#if MOZ_IS_GCC
+// GCC supports these functions.
+#  define BUILTIN_CHECKED_ARITHMETIC_SUPPORTED(x) 1
+#else
+// For CLANG, we use its own function to check for this.
+#  ifdef __has_builtin
+#    define BUILTIN_CHECKED_ARITHMETIC_SUPPORTED(x) __has_builtin(x)
+#  endif
+#endif
+#ifndef BUILTIN_CHECKED_ARITHMETIC_SUPPORTED
+#  define BUILTIN_CHECKED_ARITHMETIC_SUPPORTED(x) 0
+#endif
+
+namespace js {
+
+[[nodiscard]] inline bool SafeAdd(int32_t one, int32_t two, int32_t* res) {
+#if BUILTIN_CHECKED_ARITHMETIC_SUPPORTED(__builtin_sadd_overflow)
+  // Using compiler's builtin function.
+  return !__builtin_sadd_overflow(one, two, res);
+#else
+  // Use unsigned for the 32-bit operation since signed overflow gets
+  // undefined behavior.
+  *res = uint32_t(one) + uint32_t(two);
+  int64_t ores = (int64_t)one + (int64_t)two;
+  return ores == (int64_t)*res;
+#endif
+}
+
+[[nodiscard]] inline bool SafeSub(int32_t one, int32_t two, int32_t* res) {
+#if BUILTIN_CHECKED_ARITHMETIC_SUPPORTED(__builtin_ssub_overflow)
+  return !__builtin_ssub_overflow(one, two, res);
+#else
+  *res = uint32_t(one) - uint32_t(two);
+  int64_t ores = (int64_t)one - (int64_t)two;
+  return ores == (int64_t)*res;
+#endif
+}
+
+[[nodiscard]] inline bool SafeMul(int32_t one, int32_t two, int32_t* res) {
+#if BUILTIN_CHECKED_ARITHMETIC_SUPPORTED(__builtin_smul_overflow)
+  return !__builtin_smul_overflow(one, two, res);
+#else
+  *res = uint32_t(one) * uint32_t(two);
+  int64_t ores = (int64_t)one * (int64_t)two;
+  return ores == (int64_t)*res;
+#endif
+}
+
+[[nodiscard]] inline bool SafeMul(uint64_t one, uint64_t two, uint64_t* res) {
+#if BUILTIN_CHECKED_ARITHMETIC_SUPPORTED(__builtin_mul_overflow)
+  return !__builtin_mul_overflow(one, two, res);
+#else
+  // Hacker's Delight, 2nd edition, 2-13 Overflow detection, Fig. 2-2.
+  int zeroes =
+      mozilla::CountLeadingZeroes64(one) + mozilla::CountLeadingZeroes64(two);
+  if (zeroes <= 62) {
+    return false;
+  }
+  uint64_t half = one * (two >> 1);
+  if (int64_t(half) < 0) {
+    return false;
+  }
+  *res = half * 2;
+  if (two & 1) {
+    *res += one;
+    if (*res < one) {
+      return false;
+    }
+  }
+  return true;
+#endif
+}
+
+} /* namespace js */
+
+#endif /* util_CheckedArithmetic_h */