Microsoft KB Archive/72791

= FIX: MASM Fails to Generate Error When Real Values Are Too Small =

Article ID: 72791

Article Last Modified on 11/19/2003

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APPLIES TO


 * Microsoft Macro Assembler 6.0 Standard Edition
 * Microsoft Macro Assembler 6.0a
 * Microsoft Macro Assembler 6.0b

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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 &quot;Microsoft Macro Assembler Programmer's Guide&quot; 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

Additional query words: 5.10 5.10a 6.00 6.00a 6.00b buglist6.00 buglist6.00a buglist6.00b fixlist6.10

Keywords: kbfix KB72791

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