VC++ macro definition ## operator

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VC++ macro definition ## operator



I am trying to port our solution from VS2010 to VS2017 and have hit this compilation error with the macro definition involving token pasting operator. Here is the code below


#include “stdafx.h”

#define TEST_MACRO(str)

_T(“Error”) ## str ## _T(“””);


int main()

TEST_MACRO(“ check “);
return 0;



This compiles fine in VS2010 but fails in VS2017/VS2015. It doesn’t seem to recognize _T(“””) following str ##. I am using “multi byte character set” and hence _T(x) resolves to x ( in tchar.h ).



Can someone help me understand this issue?





for what you use _T at all ?
– RbMm
Aug 10 at 11:38


_T





Is it because you are using the “ char - replace with " Also you might need to #include <tchar.h> for the _T
– Angus Comber
Aug 10 at 11:42






what is sense of this macro at all ? what you try get ?
– RbMm
Aug 10 at 11:43





@Bathsheba - say this for microsoft. this is standard windows macro. exist large count of another such (leading underscore followed by a capital letter) macros and symbols
– RbMm
Aug 10 at 11:45





@RbMm: So long as you don't define it yourself, it's fine. Yes, didn't read the code in the question carefully enough. My bad.
– Bathsheba
Aug 10 at 11:46





3 Answers
3



Try this variant:


#define TEST_MACRO(str)

_T("Error") _T(str) _T(""");



Using ## you concatеnate your strings and for compiler it looks like: _T("Error")" check "_T("""). And " check "_T is a problem here. It is an user defined literal _T which is undefined


##


_T("Error")" check "_T(""")


" check "_T


_T





Thank you @Lex Sergeev. This solved the issue. Also using this expression with ## operator also seems to work fine. _T("Error") ## _T(str) ## _T(""").
– Tsst
Aug 10 at 13:09





Why is _T("Error") ## _T(str) ## _T(""") not an issue? _T(str) gets preprocessed to str which is "check", so the compiler should still see " check "_T
– Tsst
Aug 10 at 13:16


_T("Error") ## _T(str) ## _T(""")


" check "_T



You don't need the ##. Concatenating string literals is pointless.


##



"foo" "bar" "baz" is equivalent to "foobarbaz".


"foo" "bar" "baz"


"foobarbaz"



More likely it's stuck on the left double sharp as it tries to concatenate a closing parenthesis and str to produce a token. Have you tried to remove it?


str


#define TEST_MACRO(str) _T(“Error”) str ## _T(“””);






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