ID Number: Q73684
6.00 | 6.00
MS-DOS | OS/2
buglist6.00
Summary:
The Microsoft Macro Assembler (MASM) version 6.0 may incorrectly
initialize data that is intended to be uninitialized. The problem will
occur with every 256th data symbol in a module that is defined using
the "dup" operator. This may be illustrated with the sample program
below. To work around the problem, either avoid using the dup operator
when declaring a variable or limit the number of occurrences to less
than 256 per module.
More Information:
Uninitialized data is created by specifying the ? (question mark)
symbol as a value at declaration time. It is primarily used to
indicate that the initial value of a data symbol is unimportant. It
can also be used to indicate that a symbol is actually defined in a
separate compilation module and merely serves as a place holder for
this module.
If a segment contains only uninitialized data, the linker can reduce
the size of the resultant .EXE file by modifying the minalloc field in
the header by the corresponding amount. The loader will then allocate
the space at run-time and fix the addresses as required. Because the
assembler incorrectly initializes some data, the segment will not be
completely uninitialized; therefore, LINK copies the segment in its
entirety into the .EXE file and the resulting disk file is larger than
necessary.
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
-----------
; Assemble options needed: none
mymac macro
local ldat
ldat dd 1 dup (?)
endm
data segment
REPEAT 512
mymac
endm
data ends
end