Two month ago in GoingNative 2013 Chandler Carruth demonstrated a new tool clang-format to automatically format C++ code. The whole talk is excellent, but if you just interested in formatting watch between 24 and 32 minutes. For Visual Studio users there is now a LLVM Windows snapshot build available and the clang-format plugin for Visual Studio, see LLVM Snapshot Builds.

To demonstrate how clang-format works, on a Visual Studio 2012 machine I installed the LLVM toolchain, clang-format plugin and created a default MFC application. Below are some examples how clang-format improved the default generated code:

Original:
CPropertiesWnd::CPropertiesWnd()
{
	m_nComboHeight = 0;
}

CPropertiesWnd::~CPropertiesWnd()
{
}

clang-format:
CPropertiesWnd::CPropertiesWnd() { m_nComboHeight = 0; }

CPropertiesWnd::~CPropertiesWnd() {}

Original:
void CPropertiesWnd::AdjustLayout()
{
	if (GetSafeHwnd () == NULL || (AfxGetMainWnd() != NULL && AfxGetMainWnd()->IsIconic()))
	{
		return;
	}

	CRect rectClient;
	GetClientRect(rectClient);

	int cyTlb = m_wndToolBar.CalcFixedLayout(FALSE, TRUE).cy;

	m_wndObjectCombo.SetWindowPos(NULL, rectClient.left, rectClient.top, rectClient.Width(), m_nComboHeight, SWP_NOACTIVATE | SWP_NOZORDER);
	m_wndToolBar.SetWindowPos(NULL, rectClient.left, rectClient.top + m_nComboHeight, rectClient.Width(), cyTlb, SWP_NOACTIVATE | SWP_NOZORDER);
	m_wndPropList.SetWindowPos(NULL, rectClient.left, rectClient.top + m_nComboHeight + cyTlb, rectClient.Width(), rectClient.Height() -(m_nComboHeight+cyTlb), SWP_NOACTIVATE | SWP_NOZORDER);
}

clang-format:
void CPropertiesWnd::AdjustLayout() {
  if (GetSafeHwnd() == NULL ||
      (AfxGetMainWnd() != NULL && AfxGetMainWnd()->IsIconic())) {
    return;
  }

  CRect rectClient;
  GetClientRect(rectClient);

  int cyTlb = m_wndToolBar.CalcFixedLayout(FALSE, TRUE).cy;

  m_wndObjectCombo.SetWindowPos(NULL, rectClient.left, rectClient.top,
                                rectClient.Width(), m_nComboHeight,
                                SWP_NOACTIVATE | SWP_NOZORDER);
  m_wndToolBar.SetWindowPos(NULL, rectClient.left,
                            rectClient.top + m_nComboHeight, rectClient.Width(),
                            cyTlb, SWP_NOACTIVATE | SWP_NOZORDER);
  m_wndPropList.SetWindowPos(
      NULL, rectClient.left, rectClient.top + m_nComboHeight + cyTlb,
      rectClient.Width(), rectClient.Height() - (m_nComboHeight + cyTlb),
      SWP_NOACTIVATE | SWP_NOZORDER);
}

Original:
m_wndToolBar.SetPaneStyle(m_wndToolBar.GetPaneStyle() & ~(CBRS_GRIPPER | CBRS_SIZE_DYNAMIC | CBRS_BORDER_TOP | CBRS_BORDER_BOTTOM | CBRS_BORDER_LEFT | CBRS_BORDER_RIGHT));

clang-format:
  m_wndToolBar.SetPaneStyle(m_wndToolBar.GetPaneStyle() &
                            ~(CBRS_GRIPPER | CBRS_SIZE_DYNAMIC |
                              CBRS_BORDER_TOP | CBRS_BORDER_BOTTOM |
                              CBRS_BORDER_LEFT | CBRS_BORDER_RIGHT));

clang-format is also highly customizable for your particular coding style, see Clang-Format Style Options. You can create a .clang-format or _clang-format file with options like IndentWidth: 4, BreakBeforeBraces: Allman and place this file to the source file directory or one of its parent directories.

The Tools.ClangFormat command from the extensions formats the cursor line when no text is selected or the selected lines. In my experience it works best when the whole document is selected. I want to investigate how to format the whole document without manually selecting it first. I also want to run formatting in other Visual Studio versions, primarily in Visual Studio 2008, Visual Studio 2010 and Visual Studio 2013.

If you use Visual Studio 2012, you can try clang-format right now.

Update: The corresponding Reddit discussion thread for this article describes how to run the ClangFormat extension in Visual Studio 2013 if you don’t want to wait for an official update.

Update 2 (November 27, 2013): Manuel Klimek has added support for VS 2010 and VS 2013 to the ClangFormat extension. You can download it from the official page.