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diff --git a/js/src/irregexp/RegExpStack.h b/js/src/irregexp/RegExpStack.h
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+++ b/js/src/irregexp/RegExpStack.h
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+ * vim: set ts=8 sts=4 et sw=4 tw=99: */
+
+// Copyright 2009 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef V8_REGEXP_STACK_H_
+#define V8_REGEXP_STACK_H_
+
+#include "jspubtd.h"
+#include "js/Utility.h"
+
+namespace js {
+namespace irregexp {
+
+class RegExpStack;
+
+// Maintains a per-thread stack area that can be used by irregexp
+// implementation for its backtracking stack.
+//
+// Since there is only one stack area, the Irregexp implementation is not
+// re-entrant. I.e., no regular expressions may be executed in the same thread
+// during a preempted Irregexp execution.
+class RegExpStackScope
+{
+  public:
+    // Create and delete an instance to control the life-time of a growing stack.
+
+    // Initializes the stack memory area if necessary.
+    explicit RegExpStackScope(JSRuntime* rt);
+
+    // Releases the stack if it has grown.
+    ~RegExpStackScope();
+
+  private:
+    RegExpStack* regexp_stack;
+};
+
+class RegExpStack
+{
+  public:
+    // Number of allocated locations on the stack above the limit.
+    // No sequence of pushes must be longer that this without doing a stack-limit
+    // check.
+    static const int kStackLimitSlack = 32;
+
+    RegExpStack();
+    ~RegExpStack();
+    bool init();
+
+    // Resets the buffer if it has grown beyond the default/minimum size.
+    void reset();
+
+    // Attempts to grow the stack by at least kStackLimitSlack entries.
+    bool grow();
+
+    // Address of allocated memory.
+    const void* addressOfBase() { return &base_; }
+    const void* addressOfLimit() { return &limit_; }
+
+    void* base() { return base_; }
+    void* limit() { return limit_; }
+
+  private:
+    // Artificial limit used when no memory has been allocated.
+    static const uintptr_t kMemoryTop = static_cast<uintptr_t>(-1);
+
+    // Minimal size of allocated stack area, in bytes.
+    static const size_t kMinimumStackSize = 1 * 1024;
+
+    // Maximal size of allocated stack area, in bytes.
+    static const size_t kMaximumStackSize = 64 * 1024 * 1024;
+
+    // If size > 0 then base must be non-nullptr.
+    void* base_;
+
+    // Length in bytes of base.
+    size_t size;
+
+    // If the stack pointer gets above the limit, we should react and
+    // either grow the stack or report an out-of-stack exception.
+    // There is only a limited number of locations above the stack limit,
+    // so users of the stack should check the stack limit during any
+    // sequence of pushes longer than this.
+    void* limit_;
+
+    void updateLimit() {
+        MOZ_ASSERT(size >= kStackLimitSlack * sizeof(void*));
+        limit_ = static_cast<uint8_t*>(base()) + size - (kStackLimitSlack * sizeof(void*));
+    }
+};
+
+bool
+GrowBacktrackStack(JSRuntime* rt);
+
+}}  // namespace js::irregexp
+
+#endif  // V8_REGEXP_STACK_H_