The value indicates the maximum alignment (in bytes) for data elements within common blocks and standard numeric sequence types.
A standard numeric sequence type is a derived type containing a SEQUENCE statement and only default component data types ( INTEGER, REAL, DOUBLEPRECISION, COMPLEX without KIND= or * size) . Any other type, such as REAL*8, will make the type non-standard.
For example, -aligncommon=4 would align data elements with natural alignments of 4 bytes or more on 4-byte boundaries.
This option does not affect data with natural alignment smaller than the specified size.
Without -aligncommon, the compiler aligns elements in common blocks and numeric sequence types on (at most) 4-byte boundaries.
Specifying -aligncommon without a value defaults to 1 - all common block and numeric sequence type elements align on byte boundaries (no padding between elements).
-aligncommon=16 reverts to -aligncommon=8 on platforms that are not 64-bit enabled.