FIX: MASM Fails to Generate Error When Real Values Are Too Small (72791)
The information in this article applies to:
- Microsoft Macro Assembler (MASM) 6.0
- Microsoft Macro Assembler (MASM) 6.0a
- Microsoft Macro Assembler (MASM) 6.0b
This article was previously published under Q72791 SYMPTOMS
The Microsoft Macro Assembler (MASM) may fail to generate an error
when a floating-point value is outside the range of the minimum
allowable values.
As documented on page 142 of the "Microsoft Macro Assembler
Programmer's Guide" included with version 6.0, the limits when
using the 4-byte REAL4 (or DD), 8-byte REAL8 (or DQ), or the
10-byte REAL10 (or DT) are as follows:
Size Low High
---- --- ----
4 byte 1.18E-38 3.40E+38
8 byte 2.23E-308 1.79E+308
10 byte 3.37E-4932 1.18E+4932
However, MASM versions 5.1, 5.1a, 6.0, 6.0a, and 6.0b fail to generate
an error when exceeding the low end of this range until a value of
3.37E-32752 or smaller for the 4 and 8-byte types and a value of
3.37E-32746 or smaller for the 10-byte type.
STATUS
Microsoft has confirmed this to be a problem in MASM versions 5.1,
5.1a, 6.0, 6.0a, and 6.0b. This problem was corrected in MASM for
MS-DOS version 6.1.
MORE INFORMATION
The sample program below may be used to illustrate this problem. In
the code, two of each of the 4-, 8-, and 10-byte data types are
declared and initialized. For each type, one initializing value is
used that correctly causes an error, while the other similar
initializing value fails to cause an error, even though it should.
The declaration of n1, n3, and n5 correctly result in the following
error in MASM version 6.0, 6.0a, and 6.0b:
error A2071: initializer magnitude too large for specified size
MASM versions 5.1 and 5.1a are not as explicit in their error message,
but they correctly generate the following overflow error for n1, n3,
and n5:
error A2029: division by 0 or overflow
Neither MASM version 5.1, 5.1a, 6.0, 6.0a, or 6.0b generates an error
(as they should) on the declaration of n2, n4, and n6. (These versions
fail to produce the expected error for any number smaller than the
values listed above for each data type.)
Sample Code
; Assemble options needed: none
.MODEL large
.STACK 4096
.DATA
n1 DD 1.18E-32752 ;Causes error
n2 DD 1.18E-32751 ;Should cause error, but doesn't
n3 DQ 2.23E-32752 ;Causes error
n4 DQ 2.23E-32751 ;Should cause error, but doesn't
n5 DT 3.37E-32746 ;Causes error
n6 DT 3.37E-32745 ;Should cause error, but doesn't
.CODE
start:
mov ax, 4C00h
int 21h
END start
| Modification Type: | Minor | Last Reviewed: | 11/19/2003 |
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| Keywords: | kbfix KB72791 |
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