IF1 and IF2
IF1 block is evaluated on first assembly pass.
IF2 block is evaluated on every assembly pass if OPTION:SETIF2 is TRUE.
Syntax
IF1;;
IF2;;
Remarks
See IF for complete syntax.
Unlike version 5.1, MASM 6.1 and above do most of its work on its first pass, then performs as many subsequent passes as necessary. In contrast, MASM 5.1 always assembles in two source passes. As a result, you may need to revise or delete some pass-dependent constructs under MASM 6.1 and above.
Two-Pass Directives
To assure compatibility, MASM 6.1 and above support 5.1 directives referring to two passes. These include .ERR1, .ERR2, IF1, IF2, ELSEIF1, and ELSEIF2. For second-pass constructs, you must specify OPTION SETIF2. Without OPTION SETIF2, the IF2 and .ERR2 directives cause an error:
.ERR2 not allowed : single-pass assembler
MASM 6.1 and above handle first-pass constructs differently. It treats the .ERR1 directive as .ERR, and the IF1 directive as IF.