INFO: C Ignores Preprocessor Directives Inside of Comments

• The Microsoft C/C++ Compiler (CL.EXE)
  • 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, 16-bit edition, versions 1.0, 1.5, 1.51
  • Microsoft Visual C++, 32-bit Editions, 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");
} 

Additional query words: 8.00 8.00c 9.00 9.10

Keywords          : kbcode kbCompiler kbVC100 kbVC150 kbVC151 kbVC200 kbVC210 kbVC400 kbVC500 
Version           : MS-DOS:6.0,6.00a,6.00ax,7.0; OS/2:6.0,6.00a; WINDOWS:1.0,1.5,1.51; WINDOWS NT:1.0,2.0,2.1,4.0,5.0
Platform          : MS-DOS NT OS/2 WINDOWS 
Issue type        : kbinfo 

Last Reviewed: July 5, 1999