BUG: Trailing Commas May Cause Incorrect Error Messages

ID: Q111500

The information in this article applies to:

Microsoft Macro Assembler for MS-DOS, versions 6.1, 6.1a, 6.11
Microsoft Macro Assembler (MASM) for Windows NT, version 6.11

SYMPTOMS

If extra trailing commas are placed at the end of a data declaration statement, the Microsoft Macro Assembler (MASM) may generate incorrect error messages, which can include:

error A2207: missing right parenthesis in expression
error A2081: missing operand after unary operator
error A2206: missing operator in expression
error A2050: real or BCD number not allowed

The message given may depend upon the surrounding code. In some cases the incorrect message is only given when a listing file is generated (the /Fl switch is used). In other cases the error messages may flag the wrong line.

RESOLUTION

If an error message seems incorrect, check the indicated line and the surrounding lines for extra or improperly placed commas.

STATUS

Microsoft has confirmed this to be a problem in MASM versions 6.1x. We are researching this problem and will post new information here in the Microsoft Knowledge Base as it becomes available.

MORE INFORMATION

The expected error message for extra commas at the end of a data declaration statement is:

error A2009: syntax error in expression

Note that the incorrect errors only occur when more than one trailing comma is used.

If there is a single trailing comma and the following line is blank or a comment then no error is reported. The trailing comma indicates that the data on the following line should be concatenated to the previous data. A blank or comment line is ignored by MASM and so nothing is done. However, if a single comma occurs and the next line is not blank or a comment and does not contain correct data for the type being allocated, the correct error will be generated. For example


   db "Hello",
   nop

correctly generates:

error A2008: syntax error : nop

The following sample illustrates several possible incorrect error messages when assembled with MASM 6.1x. The error messages and their locations are not shown in the sample code as comments because adding the comments will change the behavior of MASM.

Sample Code


;Assembly options needed: /c /Fl

.model small

.data
   db "1",,

   db "1",
      "2",,

   db "1",,
      "2",

   db "1",
      "2",,
      "!"

end

Additional query words: 6.10 6.10a buglist6.10 buglist6.11 buglist6.20

Keywords :
Version : :6.1,6.11,6.1a
Platform :
Issue type :