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Datas.asm(854): error: Must be a constant integer expression.
strlen1 EQU ($ - str) ; will not work as in MASM; the tokens (, $, -, str, ) are assigned to strlen1, but no "current location" is associated with $ at this point !
The special here token ($) holds the current location in the active code or data section.Note! The here token should only be used in instructions or data directives. It will not work as expected if used in the EQU directive - only the token will be stored, not the current location.