FIX: Incorrect Code With TYPE and SI Index Register
ID: Q59374
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The information in this article applies to:
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Microsoft Macro Assembler for MS-DOS, versions 5.1, 5.1a
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Microsoft Macro Assembler for OS/2, versions 5.1, 5.1a
SYMPTOMS
An incorrect opcode is generated by the Microsoft Macro Assembler (MASM)
versions 5.1 and 5.1a when using the TYPE operator and the SI register are
used in an indirect memory operand.
STATUS
Microsoft has confirmed this to be a problem in MASM versions 5.1 and 5.1a.
This problem was corrected in MASM version 6.0.
MORE INFORMATION
The type operator returns a number that represents the type of an
expression. This is normally the size of the variable. For example,
a variable declared as dw will cause TYPE to return the number 2.
Each of the CMP instructions in the sample below should produce the
exact same encoding. Verify with a listing file that an incorrect
encoding is produced. The opcode portion of the instruction is 3b84
in the correct examples and 3b06 in the incorrect examples.
Sample Code
; Assemble options needed: none
.MODEL small
.STACK 4096 ; Allocate 4K stack space
.DATA
var1 dw 0
.CODE
main proc
MOV ax, @data ; Set up the DS register
MOV ds, ax ;
CMP ax,var1[si]+type var1 ; Incorrect code generated
CMP ax,var1[si]+(type var1) ; Incorrect code generated
CMP ax,var1[si]+[type var1] ; Incorrect code generated
CMP ax,type var1+var1[si] ; correct code generated
CMP ax,var1[si+type var1] ; correct code generated
CMP ax,var1[si]+2 ; correct code generated
CMP ax,var1[si+2] ; correct code generated
main ENDP
END main
Additional query words:
5.10 5.10a buglist5.10 buglist5.10a fixlist6.00
Keywords :
Version : :5.1,5.1a
Platform :
Issue type :