Is it fail-safe to use CString as parameter type for the method CStringT::Format?

Question

I am using the following method: CStringT::Format.

Is it fail-safe to use CString as parameter type, just like in the following?

CString a = _T("This is a %s. And it %s.");  
CString b = _T("test");  
CString c = _T("works");  
  
CString str;  
str.Format(a, b, c);  
  
// str == "This is a test. And it works."  

If it is fail-safe, please also provide a reason for this fact.

Answer 1

Hi，

According to the Doc:

You can freely substitute CStringT objects for PCXSTR function arguments.

Whenever a function parameter expects a constant C-style string, you can pass a CStringT object, that is implicitly converted by invoking the operator PCXSTR().

For more details I suggest you could refer to the link: https://stackoverflow.com/questions/48245284/using-cstring-object-in-cstringformat

Best Regards,

Jeanine

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Answer 2

Even if sizeof(CString) is the size of a pointer, and the only member of CString is a pointer to zero-terminated string or null, the documentation recommends: “[…] it is essential that you use an explicit type cast when passing a CString object to a function that takes a variable number of arguments”. See: https://learn.microsoft.com/en-us/cpp/atl-mfc-shared/cstring-operations-relating-to-c-style-strings?view=msvc-160#_core_using_cstring_objects_with_variable_argument_functions.