INFO: C Ignores Preprocessor Directives Inside of Comments

• 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, 1.51 - Microsoft Visual C++ 32-bit Edition, versions 1.0, 2.0, 2.1, 4.0, 5.0

SUMMARY

If a preprocessor directive is contained in a comment, the Microsoft C compiler may generate a message similar to the following:

   fatal error C1004: unexpected end-of-file found

MORE INFORMATION

This is the expected behavior. The message is generated because the compiler evaluates comments before preprocessor directives, thereby ignoring a preprocessor directive within a comment block.

The sample code below illustrates this situation. The #endif directive is inside of a comment because the first comment is missing a closing comment delimiter (*/). The compiler generates a C1004 error when it reaches the end of the file and has not encountered an #endif directive to match the #if directive.

Sample Code

   /* Compile options needed: none
   */

   void main ()
   {
   #if 0
     /* comment begins but doesn't end
      printf ("here 0\n");
   #endif
     /* comment */
      printf ("here 2\n");
   }