FIX: Incorrectly Generated A4100: Impure Memory ReferenceLast reviewed: September 11, 1997Article ID: Q59567 |
5.00 5.10 5.10a | 5.00 5.10 5.10a
MS-DOS | OS/2kbtool kbfixlist kbbuglist The information in this article applies to:
SYMPTOMSMicrosoft Macro Assembler (MASM) may generate the following warning
A4100: Impure memory referenceon a line where data is being accessed from the code segment, not where it is being stored.
STATUSMicrosoft has confirmed this to be a problem in MASM versions 5.0, 5.1, and 5.1a. This problem was corrected in MASM version 6.0.
MORE INFORMATIONWriting data to the code segment is acceptable in real mode; however, it may cause problems in protected (priviledged) mode. The /P option tells MASM 5.0, 5.1, and 5.1a to generate warning messages if an attempt is made to store data in the code segment when operating in protected mode. This is called an impure memory reference. Note that in MASM 6.0, checking for impure memory references is no longer enabled by a command-line option, but by OPTION READONLY. The equivalent warning message in MASM 6.0 would be A4000: cannot modify READONLY segment.
Sample Code; Assemble options needed: none .MODEL small .286p .CODE mov al, cs:[bp] mul word ptr cs:[bp+2] ; flagged as an errorEND
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Additional reference words: 5.00 5.10 5.10a buglist5.00 buglist5.10
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