Microsoft KB Archive/79821

= FIX: MASM 6.0 May Incorrectly Generate A4000 for CMP =

Article ID: 79821

Article Last Modified on 10/29/2003

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APPLIES TO


 * Microsoft Macro Assembler 6.0 Standard Edition

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This article was previously published under Q79821



SYMPTOMS
Microsoft Macro Assembler (MASM) version 6.0 will incorrectly generate the following error when the sample code below is assembled:

A4000: cannot modify READONLY segment



CAUSE
This problem occurs because the segment is tagged as READONLY, and MASM treats the CMP instruction as if it modifies memory. This is incorrect behavior because the CMP instruction does not modify any memory.



RESOLUTION
To work around this problem, either remove the READONLY tag from the segment or ignore the warning when it is generated for CMP instructions.



STATUS
Microsoft has confirmed this to be a problem in MASM version 6.0. This problem was corrected in MASM version 6.0a.



MORE INFORMATION
The sample code below reproduces the problem.

Sample Code
; Assemble options needed: none

code   SEGMENT word public readonly 'code' ASSUME cs:code cmp word ptr cs:[di], 0 code   ENDS

END

Additional query words: 6.00 buglist6.00 fixlist6.00a

Keywords: kbfix KB79821

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