BUG: Intrinsic Version of strcmp May Return Incorrect Result

ID: Q167326

The information in this article applies to:

Microsoft Visual C++, 32-bit Editions, versions 5.0, 6.0

SYMPTOMS

Explicitly referencing the Null character in the second argument of strcmp causes the intrinsic version of strcmp to incorrectly report the two arguments are not equal. Please see the sample code below.

RESOLUTION

Use one of the following two workarounds:

Do not explicitly reference the Null character.

Do not use the intrinsic version of strcmp.

Please see the "MORE INFORMATION" section and sample code below.

STATUS

Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article.

MORE INFORMATION

You can enable intrinsic functions either by using of the /Oi compiler switch or #pragma intrinsic. To disable intrinsic functions, remove the /Oi compiler switch, add /Oi-, or use #pragma function to force a function call on a function by function basis. Please see the sample code below for use of the #pragma function.

Sample Code


   /* Build Options: /Oi */ 
   #include <stdio.h>
   #include <string.h>
   // uncomment the following line for workaround #2
   //#pragma function(strcmp)

   int main(void)
   {
      char somestr [15]  = "Some String";

      somestr[1] = 0;

   // change the following to strcmp(somestr,"S") for workaround #1
      if (strcmp(somestr,"S\0") == 0)
         printf("match: correct\n");
      else
         printf("no match: incorrect\n");
      return 0;
   }

Note that a more common use of an embedded Null character may be to compare a string to "\0" to see if it is an empty string. For the first workaround above, compare it to "" instead.

Additional query words:

Keywords : kbcode kbprg kbVC500bug kbVC600bug
Version : winnt:5.0,6.0
Platform : winnt
Issue type : kbbug