BUG: Cannot Cast Double to int for Use in an Array Declarator

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This article was previously published under Q142493

SYMPTOMS

The compiler generates the following error when you type cast a 'const float' or 'const double' to 'const int' in an array declarator:

error C2057: expected constant expression

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RESOLUTION

To work around this problem, use a #defined double value in place of a const double. See the "Workaround Sample Code" section for an example.

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

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MORE INFORMATION

Sample Code to Demonstrate Problem

   /* Compile options needed: /c
   */ 

   const double d_max = 5.55;
   int arr[(const int) d_max];   // Gives C2057 here

   // The following code also gives the error:
   const double d_max = 5.55;
   const int imax = (const int) d_max;

   int arr[imax];   // Gives C2057 here

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Workaround One - Sample Code

   #define D_MAX 5.55
   const int imax = (const int) D_MAX;
   int arr[imax];

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Workaround Two - Sample Code

   #define D_MAX 5.55
   int arr[(const int) D_MAX];

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APPLIES TO

Microsoft Visual C++ 4.0 Professional Edition
Microsoft Visual C++ 4.1 Subscription
Microsoft Visual C++ 4.2 Professional Edition
Microsoft Visual C++ 4.2 Enterprise Edition
Microsoft Visual C++ 5.0 Learning Edition
Microsoft Visual C++ 5.0 Enterprise Edition
Microsoft Visual C++ 5.0 Professional Edition

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kbbug kbcompiler kbcpponly KB142493

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Retired KB Content Disclaimer

This article was written about products for which Microsoft no longer offers support. Therefore, this article is offered "as is" and will no longer be updated.

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