Replying to an old message by Paul Gilmartin:
How many passes does HLASM make over the source?
Two passes.
This could lead to a situation where the displacements oscillate
back and forth for each pass.
Similar problems exist with the old-fashioned type attribute.
I can code a test which, depending on the type attribute,
defines that symbol with a different type. This really ought
to cause an assembly error.
**--> Not at all! The T attribute is defined to return the type
of a symbol, provided it is pre-defined. That is, the symbol
must be defined at a source location before the T' type reference
is made to it. This is because the assembler needs to evaluate
the T' reference in the first pass, therefore the label must be
defined (hlasm must have processed its definition).
Look-ahead mode cannot be used, as the label may be
defined using conditional assembly - there might be
conflicting definitions - thus look-ahead might yield the
wrong variant of the defiinition.
What you do in your own macro code is your own
business, the assembler is in no position to tell whether
or not your code is in error, or you ar purposely doing
something that may or may not look like an error to
someone else.
Anyway - if you want to use attribute references like T'
then define your DSECTs at the top of your program,
rather than at the bottom. It will allow you to properly make
use of such references, it will allow proper derivation
(or inheritance) of field characteristics, et cetera.
On top of that, it severely reduces the need for hlasm
to use look-ahead mode, which shortens execution time
of your assemblies, and also saves processor cycles...
Cheers,
Abe Kornelis.
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-- gil
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