Microsoft KB Archive/68143

= PRB: Stringize Operator Fails to Insert Backslashes =

Article ID: 68143

Article Last Modified on 7/5/2005

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APPLIES TO


 * Microsoft Visual C++ 1.0 Professional Edition
 * Microsoft Visual C++ 1.5 Professional Edition
 * Microsoft Visual C++ 2.0 Professional Edition
 * Microsoft Visual C++ 2.1
 * Microsoft Visual C++ 4.0 Standard Edition
 * Microsoft Visual C++ 5.0 Enterprise Edition
 * Microsoft Visual C++ 6.0 Enterprise Edition
 * Microsoft Visual C++ 5.0 Professional Edition
 * Microsoft Visual C++ 6.0 Professional Edition
 * Microsoft Visual C++ 6.0 Standard Edition

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This article was previously published under Q68143





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 &quot; 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:
 * 1) define print_filename(x) printf(#x);

main { print_filename(d:\test\sscanf.c) } Preprocessor Output:   printf(&quot;d:\test\sscanf.c&quot;); Expected Output:   printf(&quot;d:\\test\\sscanf.c&quot;); Example 2:
 * 1) define print_filename(x) printf(#x);

main {  print_filename(This: \&quot; prints an escaped double quote mark) } Preprocessor Output for C Compiler version 6.0:   printf(&quot;This: \\&quot; prints an escaped double quote mark&quot;) 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(&quot;This: \\\&quot; prints an escaped double quote mark&quot;) Example 3:
 * 1) define print_stuff(x) printf(#x);

main {  print_stuff(I am printing a quote: &quot;) } Preprocessor Output:

error C2001: newline in constant

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

Expected Output:   printf(&quot;I am printing a quote: \&quot;&quot;);

Keywords: kblangc kbprb KB68143

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