INFO: Line Continuation Evaluated Before Inline Comment

• The Microsoft C/C++ Compiler (CL.EXE) included with: - Microsoft C for MS-DOS, versions 6.0, 6.0a, 6.0ax - Microsoft C for OS/2, versions 6.0, 6.0a - Microsoft C/C++ for MS-DOS, version 7.0 - Microsoft Visual C++ for Windows, versions 1.0, 1.5 - Microsoft Visual C++ 32-bit Edition, versions 1.0, 2.0, 4.0, 5.0

SUMMARY

To maintain ANSI compliance, the above C versions evaluate line continuation characters "\" before inline comment tokens "//". This is a change from C version 5.1 behavior, which ignores line continuation characters within inline comments. This order of evaluation may results in the following error in the sample below:

   error C2065: 'INT2' : undeclared identifier

MORE INFORMATION

Section 2.1.1.2 of the ANSI Draft proposal (dated December 7, 1988) states the order in which source code translation is to take place. The second and third steps are paraphrased below.

   2. Each instance of a new-line character and an immediately
      preceding backslash character is deleted, splicing physical
      source lines to form logical source lines. ...

   3. The source file is decomposed into preprocessing tokens and
      sequences of white-space characters... Each comment is replaced
      by one space character.

Sample Code

   #include <stdio.h>

   #define INT1 1          //    Inline comment    \
   #define INT2 2    //  This line is ignored  \

   void main(void)
   {
      printf("%d %d \n",INT1,INT2);
   }