Q31448: Array Index Multiplication with Integers Causes Link Error

Article: Q31448
Product(s): See article
Version(s): 5.00 5.10
Operating System(s): MS-DOS
Keyword(s): ENDUSER | TAR77788 | mspl13_c
Last Modified: 16-JUN-1988

When the following program is compiled and linked, the linker
generates the error "L2029 -unresolved external for the variable
_arr." However, the array appears to be declared legally. The
following code generates the error:

   char huge arr[256*512];
   main(){}

  The problem occurs because the multiplication for the array index is
done with integers and the result of the multiplication is too large
to fit in an integer. This will result in the array index being 0
(zero). Because of this array, the following declaration

   char huge arr[256*512];

is equivalent to the following declaration:

   char huge arr[0];

   The second declaration in turn, is equivalent to the following
declaration:

   char huge arr[];

   This type of declaration will cause the compiler to generate an
explicit external reference for the array arr and force the linker to
look for the variable arr.
   To solve this problem, do the multiplication for the array index
with long integers by declaring one or both of the integer constants
as long. The following is a code example:

   char huge arr[256L*512];