ID Number: Q24953
1.25 1.27 3.0x 4.00 5.00 5.10
MS-DOS
Summary:
Phase errors indicate that a relative address of a label changed
between pass 1 and pass 2 of the assembly process. They usually are
caused by improper forward references to labels. During pass 1, the
assembler will have to make assumptions (e.g. it might assume a near
jump during pass 1 if the location of a label is not known). During
pass 2, the assembler may have to change those assumptions (e.g. now
it knows that the jump is to a far label). If this involves changing
the size of an instruction, that difference can cause a phase error.
To examine the assumptions made by the assembler on pass 1, use the
/D option to get a pass 1 listing.
More Information:
Phase errors can usually be prevented by using segment overrides or
explicit type specification, as shown in the following examples:
jmp dword ptr far_label ;jump to far label
mov ax, word ptr label