Create copy of context record before passing it to StackWalk64

base/debug/stack_trace_win.cc

 // 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.
 
 #include "base/debug/stack_trace.h"
 
 #include <windows.h>
 #include <dbghelp.h>
 
 #include <iostream>
@@ skipping 193 matching lines @@
 
 StackTrace::StackTrace() {
   // When walking our own stack, use CaptureStackBackTrace().
   count_ = CaptureStackBackTrace(0, arraysize(trace_), trace_, NULL);
 }
 
 #if defined(COMPILER_MSVC)
 #pragma optimize("", on)
 #endif
 
-StackTrace::StackTrace(EXCEPTION_POINTERS* exception_pointers) {
+StackTrace::StackTrace(const EXCEPTION_POINTERS* exception_pointers) {
   // When walking an exception stack, we need to use StackWalk64().
   count_ = 0;
+  // StackWalk64() may modify context record passed to it, so we will
+  // use a copy.
+  CONTEXT context_record = *exception_pointers->ContextRecord;
   // Initialize stack walking.
   STACKFRAME64 stack_frame;
   memset(&stack_frame, 0, sizeof(stack_frame));
 #if defined(_WIN64)
   int machine_type = IMAGE_FILE_MACHINE_AMD64;
-  stack_frame.AddrPC.Offset = exception_pointers->ContextRecord->Rip;
-  stack_frame.AddrFrame.Offset = exception_pointers->ContextRecord->Rbp;
-  stack_frame.AddrStack.Offset = exception_pointers->ContextRecord->Rsp;
+  stack_frame.AddrPC.Offset = context_record.Rip;
+  stack_frame.AddrFrame.Offset = context_record.Rbp;
+  stack_frame.AddrStack.Offset = context_record.Rsp;
 #else
   int machine_type = IMAGE_FILE_MACHINE_I386;
-  stack_frame.AddrPC.Offset = exception_pointers->ContextRecord->Eip;
-  stack_frame.AddrFrame.Offset = exception_pointers->ContextRecord->Ebp;
-  stack_frame.AddrStack.Offset = exception_pointers->ContextRecord->Esp;
+  stack_frame.AddrPC.Offset = context_record.Eip;
+  stack_frame.AddrFrame.Offset = context_record.Ebp;
+  stack_frame.AddrStack.Offset = context_record.Esp;
 #endif
   stack_frame.AddrPC.Mode = AddrModeFlat;
   stack_frame.AddrFrame.Mode = AddrModeFlat;
   stack_frame.AddrStack.Mode = AddrModeFlat;
   while (StackWalk64(machine_type,
                      GetCurrentProcess(),
                      GetCurrentThread(),
                      &stack_frame,
-                     exception_pointers->ContextRecord,
+                     &context_record,
                      NULL,
                      &SymFunctionTableAccess64,
                      &SymGetModuleBase64,
                      NULL) &&
          count_ < arraysize(trace_)) {
     trace_[count_++] = reinterpret_cast<void*>(stack_frame.AddrPC.Offset);
   }
 
   for (size_t i = count_; i < arraysize(trace_); ++i)
     trace_[i] = NULL;
@@ skipping 13 matching lines @@
       (*os) << "\t" << trace_[i] << "\n";
     }
   } else {
     (*os) << "Backtrace:\n";
     context->OutputTraceToStream(trace_, count_, os);
   }
 }
 
 }  // namespace debug
 }  // namespace base