UB in macros? (MS VC compiler does unbelievable tricks)

UB in macros? (MS VC compiler does unbelievable tricks)

• noahmattern

  <noobOOP@discussions.microsoft.com> wrote in message
  news:d69843ac-76b7-4797-82c1-2c0fd203c173@discussions.microsoft.com
  > Sure it does.
  > Here we go:
  > #define Yad(x) Y ## x
  > Yad(()
  > Result - error.

   

  Not surprising. Macro invocation is missing a closing paren. A () pair is treated as part of argument x, together with the rest of the translation unit (unless you happen to have an unmatched right paren in there somewhere).

  
  > Here we go again:
  > #define Yad(x) (

  > #define REDO(x) x
  > #define AREDO(x) #x A ## x
  > #define A(x) A ## REDO(x)
  > A(Yad)
  > Result - "(" A(
  > Is it conformable with C++ Standart (This trick doesnt work in gcc)
  

  I guess you mean

   

  #define Yad (

   

  (no parameter list). According to my reading of the standard, this should have produced the same error, since at one point the preprocessor should have wound up with AREDO( ( ) that it had to rescan for more macros.
  --
  With best wishes,
      Igor Tandetnik

  
  

• BPeck

  Could you please log the issue at http://lab.msdn.microsoft.com/productfeedback/default.aspx where the responsible folks can take a look
  
  Thanks in advance for taking the time to report the issue!
  
  Thanks,
    Ayman Shoukry
    VC++ Team
  
  

• Bruno Denuit - MSFT

  First arent suprising for me too, but the second :)
  
  But this bug can be usefull, should MS programmers fix it :D
  
  

• SujathaJaganathan

  Ok, I will do it.
  
  
  BEGGING MY PARDONS, there were a little error in the source code, so it's work wasnt correctly (bug wasnt seen). But now I fix it, so the bug is now seen.
  Submitted to lab.
  
  
• UB in macros? (MS VC compiler does unbelievable tricks)