Enumerating Locals
When Visual Studio is ready to populate the Locals window, it calls IDebugProperty2::EnumChildren on the IDebugProperty2 object returned from IDebugExpressionEvaluator::GetMethodProperty (see Implementing GetMethodProperty). IDebugProperty2::EnumChildren returns an IEnumDebugPropertyInfo2 object.
This implementation of IDebugProperty2::EnumChildren performs the following tasks:
Ensures this is representing a method.
Uses the guidFilter argument to determine which method to call on the IDebugMethodField object. If guidFilter equals:
guidFilterLocals, call IDebugMethodField::EnumLocals to obtain an IEnumDebugFields object.
guidFilterArgs, call IDebugMethodField::EnumArguments to obtain an IEnumDebugFields object.
guidFilterLocalsPlusArgs, synthesize an enumeration that combines the results from IDebugMethodField::EnumLocals and IDebugMethodField::EnumArguments. This synthesis is represented by the class CEnumMethodField.
Instantiates a class (called CEnumPropertyInfo in this example) that implements the IEnumDebugPropertyInfo2 interface and contains the IEnumDebugFields object.
Returns the IEnumDebugProperty2Info2 interface from the CEnumPropertyInfo object.
Managed Code
This example shows an implementation of IDebugProperty2::EnumChildren in managed code.
namespace EEMC
{
public class CFieldProperty : IDebugProperty2
{
public HRESULT EnumChildren (
uint dwFields,
uint radix,
ref Guid guidFilter,
ulong attribFilter,
string nameFilter,
uint timeout,
out IEnumDebugPropertyInfo2 properties)
{
properties = null;
IEnumDebugFields fields = null;
// If this field is a method...
if (0 != ((uint) fieldKind & (uint) FIELD_KIND.FIELD_TYPE_METHOD))
{
IDebugMethodField methodField = (IDebugMethodField) field;
// Enumerate parameters.
if (guidFilter == FilterGuids.guidFilterArgs)
{
methodField.EnumParameters(out fields);
}
// Enumerate local variables.
else if (guidFilter == FilterGuids.guidFilterLocals)
{
methodField.EnumLocals(address, out fields);
}
// Enumerate all local variables, including invisible compiler temps.
else if (guidFilter == FilterGuids.guidFilterAllLocals)
{
methodField.EnumAllLocals(address, out fields);
}
// Enumerate "this", if any, and all parameters and local variables.
else if (guidFilter == FilterGuids.guidFilterLocalsPlusArgs)
{
IDebugClassField fieldThis = null;
IEnumDebugFields parameters = null;
IEnumDebugFields locals = null;
methodField.GetThis(out fieldThis);
methodField.EnumParameters(out parameters);
methodField.EnumLocals(address, out locals);
CEnumMethodField enumMethodField =
new CEnumMethodField(fieldThis, parameters, locals);
fields = (IEnumDebugFields) enumMethodField;
}
// Enumerate only "this".
else if (guidFilter == FilterGuids.guidFilterThis)
{
IDebugClassField fieldThis = null;
methodField.GetThis(out fieldThis);
CEnumMethodField enumMethodField =
new CEnumMethodField(fieldThis, null, null);
fields = (IEnumDebugFields) enumMethodField;
}
else throw new COMException();// E_FAIL
}
// Wrap a property enumerator around the field enumerator.
CEnumPropertyInfo propertiesInfo =
new CEnumPropertyInfo(provider, address, binder, radix, fields,
(DEBUGPROP_INFO_FLAGS) dwFields);
properties = (IEnumDebugPropertyInfo2) propertiesInfo;
return COM.S_OK;
}
}
}
Unmanaged Code
This example shows an implementation of IDebugProperty2::EnumChildren in unmanaged code.
STDMETHODIMP CFieldProperty::EnumChildren(
in DEBUGPROP_INFO_FLAGS infoFlags,
in DWORD radix,
in REFGUID guidFilter,
in DBG_ATTRIB_FLAGS attribFilter,
in LPCOLESTR pszNameFilter,
in DWORD timeout,
out IEnumDebugPropertyInfo2 ** ppchildren )
{
if (ppchildren == NULL)
return E_INVALIDARG;
else
*ppchildren = 0;
//get enumeration
HRESULT hr;
IEnumDebugFields* pfields = NULL;
if (m_fieldKind & FIELD_TYPE_METHOD)
{
//-----------------------------------------------------
// A Method
IDebugMethodField* pmethod = NULL;
//enumerate the requested properties
hr = m_field->QueryInterface( IID_IDebugMethodField,
reinterpret_cast<void**>(&pmethod) );
if (FAILED(hr))
return hr;
if (guidFilter == guidFilterArgs)
{
hr = pmethod->EnumParameters( &pfields );
}
else if (guidFilter == guidFilterLocals)
{
hr = pmethod->EnumLocals( m_address, &pfields );
}
else if (guidFilter == guidFilterAllLocals)
{
hr = pmethod->EnumAllLocals( m_address, &pfields );
}
else if (guidFilter == guidFilterLocalsPlusArgs)
{
//we create a special enumerator for this
IDebugClassField* pfieldThis = NULL;
IEnumDebugFields* pparameters = NULL;
IEnumDebugFields* plocals = NULL;
pmethod->GetThis( &pfieldThis );
pmethod->EnumParameters( &pparameters );
pmethod->EnumLocals( m_address, &plocals );
CEnumMethodField* penumMethodField =
new CEnumMethodField( pfieldThis, pparameters, plocals );
if (pfieldThis != NULL)
pfieldThis->Release();
if (pparameters != NULL)
pparameters->Release();
if (plocals != NULL)
plocals->Release();
if (!penumMethodField)
{
hr = E_OUTOFMEMORY;
}
else
{
hr = penumMethodField->QueryInterface( IID_IEnumDebugFields,
reinterpret_cast<void**>(&pfields) );
penumMethodField->Release();
}
}
else if (guidFilter == guidFilterThis )
{
IDebugClassField* pfieldThis = NULL;
hr = pmethod->GetThis( &pfieldThis );
if (SUCCEEDED(hr))
{
CEnumMethodField* penumMethodField =
new CEnumMethodField( pfieldThis, NULL, NULL );
pfieldThis->Release();
if (!penumMethodField)
{
hr = E_OUTOFMEMORY;
}
else
{
hr = penumMethodField->QueryInterface( IID_IEnumDebugFields,
reinterpret_cast<void**>(&pfields) );
penumMethodField->Release();
}
}
}
else
{
hr = E_FAIL;
}
pmethod->Release();
if (hr != S_OK)
return hr;
}
//create a property info enumeration around the field enumerator
CEnumPropertyInfo* pproperties =
new CEnumPropertyInfo( m_provider, m_address, m_binder,
radix, pfields, infoFlags );
if (pfields != NULL)
pfields->Release();
if (pproperties == NULL)
return E_OUTOFMEMORY;
hr = pproperties->QueryInterface( IID_IEnumDebugPropertyInfo2,
reinterpret_cast<void**>(ppchildren) );
pproperties->Release();
return hr;
}
See Also
Concepts
Sample Implementation of Locals