is there any difference between passing a CString and passing CString.GetBuffer to a %s in a CString.Format

Question

Given

CString buffer = "";
Cstring value = "blah";

buffer.Format ("%s %s", value, value.GetBuffer());

are the two ways of passing a CString equivalent, or does passing the CString have something happening behind the scenes that causes it to be equivalent?

Answer 1

Neither one is correct. The first one seems to work, by coincidence while the latter uses a tool that serves a different purpose. The only correct way is to invoke the cast operator:

buffer.Format("%s", static_cast<LPCTSTR>(value));

Passing a CString object directly works by coincidence only since the pointer-sized value at the beginning of the object is interpreted as a pointer to a character array. The first class member of the CString class happens to be the m_pszData member - a pointer that stores the controlled sequence of characters.

GetBuffer should only be used if you have to manipulate a CStrings contents directly. Note that this returns a non-const pointer. This is often used when interfacing with C APIs (see Modifying CString Contents Directly for details).