FIX: Operator ++ In Return Statement May Cause Access Violation

View products that this article applies to.

This article was previously published under Q205681

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SYMPTOMS

A compiled program may cause access violation if it contains a function returning a struct by value, and the return expression has either a postfix increment or decrement operator.

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RESOLUTION

There following are workarounds for this problem.

Remove the postfix increment/decrement operator from the return expression.
Use the prefix increment/decrement operator.

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Microsoft has confirmed that this is a bug in the Microsoft products that are listed at the beginning of this article.

This bug was corrected in Visual Studio 6.0 Service Pack 3. For more information about Visual Studio service packs, please see the following articles in the Microsoft Knowledge Base:

194022 (http://support.microsoft.com/kb/194022/EN-US/ ) INFO: Visual Studio 6.0 Service Packs, What, Where, Why

194295 (http://support.microsoft.com/kb/194295/EN-US/ ) HOWTO: Tell That Visual Studio 6.0 Service Packs Are Installed

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MORE INFORMATION

To reproduce the problem, build and run the following sample program.



Sample
----------------

#include <stdio.h>
#include <stdlib.h>

typedef struct
{
 int   type;
 int   offset;
}
ST;

int i;

struct
{
 ST  *tab;   
 int used;  
}
STAdmin;

ST MyFunction ()
{
#ifdef WORKAROUND_1
   int temp = i++;
   return STAdmin.tab[temp];
#endif

#ifdef WORKAROUND_2
   return STAdmin.tab[++i - 1];
#endif<BR/>

   return STAdmin.tab[i++];
}

void main(void)
{
   ST a;
   int i;

   STAdmin.tab = (ST*) malloc(sizeof(ST)*10);
   STAdmin.used = 0;

   // Initialize the Array 
   for(i=0;i<10;i++)
   {
       STAdmin.tab[i].offset=i;
       printf("%d\n",STAdmin.tab[i].offset);
   }

   // Read in the Array 
   for(i=0;i<10;i++)
   {
	a = MyFunction();
	printf("%d\n",a.offset);
   }
}
// End of Sample Code

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