BUG: C1017 Occurs with /Zg and #if

The information in this article applies to:

• The Microsoft C/C++ Compiler (CL.EXE), included with:

      - Microsoft Visual C++ for Windows, versions 1.0 and 1.5
  

SYMPTOMS

A C1017 error is incorrectly generated when using /Zg and the preprocessor directive #if on an integer constant. For example, using #if 0 or #if 3 causes the following error:

   file.c(3) : fatal error C1017: invalid integer constant expression

   #define ZERO 0
   #if ZERO

RESOLUTION

The following are two possible workarounds:

• This error occurs only if the /Zg compiler switch is used. If it's not necessary, do not use /Zg with the file.

  -or-

• If the expression being evaluated is 0 (zero), then it will never evaluate to true. If the expression is nonzero, then it will always evaluate to true. It should be possible to use #ifdef instead of #if (see MORE INFORMATION below).

MORE INFORMATION

The most common reason for using an expression that always evaluates to an integer constant is to enable conditional compilation, which is dependent on a particular symbol being used. For example, the following code prints out information only when the MYDEBUG_BUILD_OPTION symbol is defined to be equal to 1:

   #include <stdio.h>

   #define MYDEBUG_BUILD_OPTION 1
   // Use #define MYDEBUG_BUILD_OPTION 0 to do a non-debug build.

   void main(void)
   {
   #if MYDEBUG_BUILD_OPTION
     printf("We are debugging\n");
   #endif
     printf("Hello world\n");
   }

   #include <stdio.h>

   #define MYDEBUG_BUILD_OPTION

   // Remove the above line to do a non-debug build, or
   // eliminate the define and use the /D compiler option
   // to define MYDEBUG_BUILD_OPTION for debug builds.

   void main(void)
   {
   #ifdef MYDEBUG_BUILD_OPTION
     printf("We are debugging\n");
   #endif
     printf("Hello world\n");
   }

STATUS

Microsoft has confirmed this to be a problem in the Microsoft C/C++ compiler versions 8.0 and 8.0c for MS-DOS. We are researching this problem and will post new information here in the Microsoft Knowledge Base as it becomes available.