BUG: Intrinsic Version of strlen() Fails

The information in this article applies to:

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

      - Microsoft C/C++ for MS-DOS, version 7.0
      - Microsoft Visual C++ for Windows, versions 1.0 and 1.5
  

SYMPTOMS

The intrinsic version of the strlen() function fails for arrays larger than 65535 bytes. The compiler options needed to reproduce the problem are /Oi and /AL, as shown with the sample code in the "MORE INFORMATION" section of this article.

RESOLUTION

The problem can be worked around using one of the following methods:

• Compile without /Oi.

  -or-

• Compile with /Od.

  -or-

• Compile with /f- in Visual C++, versions 1.0, 1.50, or 1.50.01.

  -or-

• Use #pragma function(strlen).

  -or-

• Use #pragma optimize("", off) in Visual C/C++ 1.0, 1.50, or 1.50.01.

STATUS

Microsoft has confirmed this to be a bug in the products listed above. We are researching this problem and will post new information here in the Microsoft Knowledge Base as it becomes available.

This is not a problem in Visual C++ 1.0, 32-bit Edition.

MORE INFORMATION

The following code can be used to demonstrate this problem:

Sample Code

/* Compile options needed: /Oi /AL
*/

#include <string.h>
#include <stdio.h>

// #pragma function(strlen) // This line needed to fix the problem

char _far sz65535[65536];

void main(void)

   size_t length;

   memset(sz65535, 'A', 65535U);
   sz65535[65535] = '\0';
   length = strlen( sz65535);

   printf( "Actual Length of string is 65535,\n"
           "strlen(sz65535) returned %u\n", length);
}

REFERENCE

More information on #pragma can be found in the online Help for Visual C++ or by typing "qh #pragma" at the MS-DOS prompt in C/C++, version 7.0.