[LLDB] Avoid using InitializeContext for zero-initializing a CONTEXT. NFC.

InitializeContext is useful for allocating a (potentially variable
size) CONTEXT struct in an unaligned byte buffer. In this case, we
already have a fixed size CONTEXT we want to initialize, and we only
used this as a very roundabout way of zero initializing it.

Instead just memset the CONTEXT we have, and set the ContextFlags field
manually.

This matches how it is done in NativeRegisterContextWindows_*.cpp.

This also makes LLDB run successfully in Wine (for a trivial tested
case at least), as Wine hasn't implemented the InitializeContext
function.

Differential Revision: https://reviews.llvm.org/D70742

diff --git a/lldb/source/Plugins/Process/Windows/Common/RegisterContextWindows.cpp b/lldb/source/Plugins/Process/Windows/Common/RegisterContextWindows.cpp
index 28e7a59..c3cb455 100644 (file)
--- a/lldb/source/Plugins/Process/Windows/Common/RegisterContextWindows.cpp
+++ b/lldb/source/Plugins/Process/Windows/Common/RegisterContextWindows.cpp
@@ -154,15 +154,8 @@ bool RegisterContextWindows::CacheAllRegisterValues() {
     return true;
 
   TargetThreadWindows &wthread = static_cast<TargetThreadWindows &>(m_thread);
-  uint8_t buffer[2048];
-  memset(buffer, 0, sizeof(buffer));
-  PCONTEXT tmpContext = NULL;
-  DWORD contextLength = (DWORD)sizeof(buffer);
-  if (!::InitializeContext(buffer, kWinContextFlags, &tmpContext,
-                           &contextLength)) {
-    return false;
-  }
-  memcpy(&m_context, tmpContext, sizeof(m_context));
+  memset(&m_context, 0, sizeof(m_context));
+  m_context.ContextFlags = kWinContextFlags;
   if (::SuspendThread(
           wthread.GetHostThread().GetNativeThread().GetSystemHandle()) ==
       (DWORD)-1) {