The OPTIONS directive affects data alignment and warnings about data alignment. It takes the following form:
cDEC$ OPTIONS option [option] ... cDEC$ END OPTIONS
Controls whether warnings are issued by the compiler for data that is not naturally aligned. By default, you receive compiler messages when misaligned data is encountered (/WARN=ALIGNMENT).
Controls alignment of fields in record structures and data items in common blocks. The fields and data items can be naturally aligned (for performance reasons) or they can be packed together on arbitrary byte boundaries.
{ [class =] rule } { (class = rule,...) } { ALL } { NONE }
Packs fields in records or data items in common blocks on arbitrary byte boundaries.
Naturally aligns fields in records and data items in common blocks on up to 64-bit boundaries (inconsistent with the Fortran 95/90 standard).
This keyword causes the compiler to naturally align all data in a common block, including INTEGER(8), REAL(8), and all COMPLEX data.
Naturally aligns data items in common blocks on up to 32-bit boundaries (consistent with the Fortran 95/90 standard).
This keyword only applies to common blocks; so, you can specify /ALIGN=COMMONS=STANDARD, but you cannot specify /ALIGN=STANDARD.
The OPTIONS (and accompanying END OPTIONS) directives must come after OPTIONS, SUBROUTINE, FUNCTION, and BLOCK DATA statements (if any) in the program unit, and before the executable part of the program unit.
The OPTIONS directive supersedes the compiler option that sets alignment.
For performance reasons, Compaq Fortran aligns local data items on natural boundaries. However, EQUIVALENCE, COMMON, RECORD, and STRUCTURE data declaration statements can force misaligned data. If /WARN=NOALIGNMENT is specified, warnings will not be issued if misaligned data is encountered.
If you want aligned data in common blocks, do one of the following:
If you want packed, unaligned data in a record structure, do one of the following:
An OPTIONS directive must be accompanied by an END OPTIONS directive; the directives can be nested up to 100 levels. For example:
CDEC$ OPTIONS /ALIGN=PACKED ! Start of Group A declarations CDEC$ OPTIONS /ALIGN=RECO=NATU ! Start of nested Group B more declarations CDEC$ END OPTIONS ! End of Group B still more declarations CDEC$ END OPTIONS ! End of Group A
The CDEC$ OPTIONS specification for Group B only applies to RECORDS; common blocks within Group B will be PACKED. This is because COMMONS retains the previous setting (in this case, from the Group A specification).