MASM 6.0 May Parse a Comment as a Conditional Directive

ID Number: Q72700

6.00 | 6.00

MS-DOS | OS/2

buglist6.00

Summary:

The Microsoft Macro Assembler (MASM) version 6.0 will incorrectly

parse a comment as if it were a conditional-assembly directive if the

following conditions are met:

1. There is a conditional-assembly directive (or word that is the same

as a conditional directive) inside a comment block that does not

directly follow the delimiter character and is the first thing on

the line.

2. The comment block itself is contained in a conditional-assembly

block, which will NOT be evaluated by the assembler.

When both of these conditions are true, the conditional-assembly

directive is given precedence over the comment block. The conditional

directive is treated as a keyword although it was not meant to be

treated as such.

More Information:

If the conditional-assembly directive is either IF, IFE, IFB, IFNB,

IFDEF, IFNDEF, IFIDN, or IFDIF and there is no associated ENDIF at the

beginning of another line, then the following errors will be

generated:

error A2088 : END directive required at end of file

fatal error : A1010 : unmatched block nesting : if-else

If the conditional-assembly directive is ELSE, then the following

error is generated:

error A2008 : syntax error : <the text following the ELSE>

If the conditional-assembly directive is ELSEIF, then the following

errors are generated:

error A2008 : syntax error

error A2081 : missing operand after unary operator

If the conditional-assembly directive is ENDIF, then the following

errors are generated

error A2008 : syntax error

error A2044 : invalid character in file

where the invalid character referred to is the closing delimiter.

The sample code below illustrates this problem. It meets the above

conditions, so it is parsed incorrectly and the following errors are

generated:

error A2088 : END directive required at end of file

fatal error : A1010 : unmatched block nesting : if-else

To work around the problem, make sure that the first word on the line

inside the comment block is not the same as a conditional directive.

For example, in the sample code, one solution is to change the line

"If should be ignored in a comment" to "An if should be ignored in a

comment."

Microsoft has confirmed this to be a problem in MASM version 6.0. We

are researching this problem and will post new information here as it

becomes available.

Sample Code

-----------

.model small

.stack

.code

.startup

IFDEF xyz ; xyz is not defined

COMMENT ^

If should be ignored in this comment.

^

ENDIF

.exit

END