MC＋＋ basic

[hangaround]

What does these codes mean as following?
#pragma push_macro("new ")
#undef new

[Carl Daniel [VC++ MVP]]

hangaround wrote:

What does these codes mean as following?
#pragma push_macro("new ")
#undef new

Try reading the documentation. It's online and installed with VC++.

http://msdn.microsoft.com/library/de...push_macro.asp
http://msdn.microsoft.com/library/de...fpop_macro.asp
http://msdn.microsoft.com/library/de..._directive.asp

-cd

[Jochen Kalmbach [MVP]]

Hi hangaround!

What does these codes mean as following?
#pragma push_macro("new ")
#undef new

See: push_macro
http://msdn.microsoft.com/library/en...Push_macro.asp

See: pop_macro
http://msdn.microsoft.com/library/en...fpop_macro.asp

See: undef
http://msdn.microsoft.com/library/en..._directive.asp

In short:
It saves the state of the macro "new" and then undefines this macro (so
it will use the C++ new-method).

--
Greetings
Jochen

My blog about Win32 and .NET
http://blog.kalmbachnet.de/

[hangaround]

Now see the code snippet in which that two statements stays
.......
#pragma push_macro("new ")
#undef new
CFileDialog dlg(TRUE);
dlg.m_pOFN->lpstrInitialDi r = m_strWorkingDir ;
dlg.m_pOFN->lpstrTitle = _T("Open an XMLSingle XML File");
dlg.m_pOFN->lpstrFilter = _T("XML Files (*.xml)\0*.xml\ 0");

if (IDOK == dlg.DoModal())
{
m_lbxAuthors.Re setContent();

XmlTextReader* xmlreader;
try
{
xmlreader = new XmlTextReader(d lg.GetPathName( ));
.......
since we undef the new , how can we use it in the
xmlreader = new XmlTextReader(d lg.GetPathName( ));

It confuses me.

[Carl Daniel [VC++ MVP]]

hangaround wrote:

Now see the code snippet in which that two statements stays
......
#pragma push_macro("new ")
#undef new
CFileDialog dlg(TRUE);
dlg.m_pOFN->lpstrInitialDi r = m_strWorkingDir ;
dlg.m_pOFN->lpstrTitle = _T("Open an XMLSingle XML File");
dlg.m_pOFN->lpstrFilter = _T("XML Files (*.xml)\0*.xml\ 0");

if (IDOK == dlg.DoModal())
{
m_lbxAuthors.Re setContent();

XmlTextReader* xmlreader;
try
{
xmlreader = new XmlTextReader(d lg.GetPathName( ));
......
since we undef the new , how can we use it in the
xmlreader = new XmlTextReader(d lg.GetPathName( ));

It confuses me.

new is a built-in operator in C++, but some libraries (particularly MFC)
define a macro of the same name to "hijack" memory allocation and hook their
own memory tracking system in.

In this case, the #undef is simply to make sure that it's the built-in new
that's being used, not any macro by that name.

-cd

[hangaround]

aha! I know, millions of thanks!