DOCUMENT:Q68143  14-NOV-2001  [visualc]
TITLE   :PRB: Stringize Operator Fails to Insert Backslashes
PRODUCT :Microsoft C Compiler
PROD/VER::1.0,1.5,2.0,2.1,4.0,5.0,6.0
OPER/SYS:
KEYWORDS:kbLangC kbVC100 kbVC150 kbVC200 kbVC210 kbVC400 kbVC500

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The information in this article applies to:

 - Microsoft C/C++ compiler for MS-DOS 
 - Microsoft Visual C++, versions 1.0, 1.5, 2.0, 2.1, 4.0 
 - Microsoft Visual C++, 32-bit Enterprise Edition, versions 5.0, 6.0 
 - Microsoft Visual C++, 32-bit Professional Edition, versions 5.0, 6.0 
 - Microsoft Visual C++, 32-bit Learning Edition, version 6.0 
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SYMPTOMS
========

The Microsoft C and C/C++ compilers support the use of the stringizing
preprocessor operator only in macros that take arguments. If a # precedes a
formal parameter in the definition of a macro, the actual argument is enclosed
in double quotation marks and treated as a string when the macro is expanded.

If the argument contains characters that normally must be preceded by a backslash
(\) when appearing in a string (such as " or \), the backslash should be
automatically inserted. However, there are many cases where the preprocessor
fails to do this.

STATUS
======

This behavior is by design.

MORE INFORMATION
================

Following are some sample macros that use the stringizing operator. They are
followed by a line showing the incorrect preprocessor output (compiling with /P)
and the output that was expected.

Sample Code
-----------

Example 1:

   #define print_filename(x) printf(#x);

   main()
   {
    print_filename(d:\test\sscanf.c)
   }

Preprocessor Output:

   printf("d:\test\sscanf.c");

Expected Output:

   printf("d:\\test\\sscanf.c");

Example 2:

   #define print_filename(x) printf(#x);

   main()
   {
      print_filename(This: \" prints an escaped double quote mark)
   }

Preprocessor Output for C Compiler version 6.0:

   printf("This: \\" prints an escaped double quote mark")

Preprocessor Output for C/C++ Compilers, Versions 7.0 and above:

   error C2001: newline in constant
   fatal error C1057: unexpected end-of-file in macro expansion

Expected Output:

   printf("This: \\\" prints an escaped double quote mark")

Example 3:

   #define print_stuff(x) printf(#x);

   main()
   {
      print_stuff(I am printing a quote: ")
   }

Preprocessor Output:

   error C2001: newline in constant
   fatal error C1057: unexpected end-of-file in macro expansion

Expected Output:

   printf("I am printing a quote: \"");

Additional query words:

======================================================================
Keywords          : kbLangC kbVC100 kbVC150 kbVC200 kbVC210 kbVC400 kbVC500 
Technology        : kbVCsearch kbVC400 kbAudDeveloper kbZNotKeyword8 kbvc150 kbvc100 kbZNotKeyword3 kbVC500 kbVC600 kbVC200 kbVC210 kbVC32bitSearch kbVC500Search
Version           : :1.0,1.5,2.0,2.1,4.0,5.0,6.0
Issue type        : kbprb

=============================================================================

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