Copy the register context before calling StackWalk64

base/debug/stack_trace.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef BASE_DEBUG_STACK_TRACE_H_
 #define BASE_DEBUG_STACK_TRACE_H_
 
 #include <iosfwd>
 #include <string>
 
@@ skipping 34 matching lines @@
   // Creates a stacktrace from an existing array of instruction
   // pointers (such as returned by Addresses()).  |count| will be
   // trimmed to |kMaxTraces|.
   StackTrace(const void* const* trace, size_t count);
 
 #if defined(OS_WIN)
   // Creates a stacktrace for an exception.
   // Note: this function will throw an import not found (StackWalk64) exception
   // on system without dbghelp 5.1.
   StackTrace(_EXCEPTION_POINTERS* exception_pointers);
-  StackTrace(_CONTEXT* context);
+  StackTrace(const _CONTEXT* context);
 #endif
 
   // Copying and assignment are allowed with the default functions.
 
   ~StackTrace();
 
   // Gets an array of instruction pointer values. |*count| will be set to the
   // number of elements in the returned array.
   const void* const* Addresses(size_t* count) const;
 
   // Prints the stack trace to stderr.
   void Print() const;
 
 #if !defined(__UCLIBC__)
   // Resolves backtrace to symbols and write to stream.
   void OutputToStream(std::ostream* os) const;
 #endif
 
   // Resolves backtrace to symbols and returns as string.
   std::string ToString() const;
 
  private:
 #if defined(OS_WIN)
-  void InitTrace(_CONTEXT* context_record);
+  void InitTrace(const _CONTEXT* context_record);
 #endif
 
   // From http://msdn.microsoft.com/en-us/library/bb204633.aspx,
   // the sum of FramesToSkip and FramesToCapture must be less than 63,
   // so set it to 62. Even if on POSIX it could be a larger value, it usually
   // doesn't give much more information.
   static const int kMaxTraces = 62;
 
   void* trace_[kMaxTraces];
 
@@ skipping 16 matching lines @@
                          int base,
                          size_t padding);
 #endif  // defined(OS_POSIX) && !defined(OS_ANDROID)
 
 }  // namespace internal
 
 }  // namespace debug
 }  // namespace base
 
 #endif  // BASE_DEBUG_STACK_TRACE_H_