PRB: SIZE Operator Value (11910)
The information in this article applies to:
- Microsoft Macro Assembler (MASM) 4.0
- Microsoft Macro Assembler (MASM) 5.0
- Microsoft Macro Assembler (MASM) 5.1
- Microsoft Macro Assembler (MASM) 6.0
This article was previously published under Q11910 SYMPTOMS
When trying to get the length of a text string, using the SIZE operator can
produce undesired results. In the example below, MSG_LEN is set to a value
of 1, but it seems it should be set to a value of 11:
MSG DB 'Darth Vader'
MSG_LEN EQU SIZE MSG
CAUSE
The value of MSG_LEN should be 1. The SIZE operator is defined to be the
LENGTH * TYPE as stated in the documentation. The expression, LENGTH MSG,
will be equal to 1 (when applied to a data label, the LENGTH operator
returns the number of elements created by the DUP operator; otherwise it
returns 1) and the expression, TYPE MSG, will be equal to 1. Therefore, the
variable MSG_LEN will be equal to 1.
RESOLUTION
In Macro Assembler version 6.0, the SIZEOF operator can be used to calulate
the total number of bytes allocated to a data item. In versions prior to
6.0, a simple way to calculate the value you want is as follows:
MSG DB 'Darth Vader'
MSG_LEN EQU $-MSG
| Modification Type: | Minor | Last Reviewed: | 2/11/2004 |
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| Keywords: | KB11910 |
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