What the ANSI standard says.
On Fri, 24 Aug 2012 12:37:05 +0200, Bernd Oppolzer wrote:
>
>we have some modules written in C that have large arrays with constants.
>For some reasons we are forced to compile those modules using the RENT
>compiler option, which moves those arrays to the WSA (writable storage
>area)
>at runtime, which is not a desired behaviour, because this way, the
>storage is
>occupied twice - once �n the WSA and second in the initialization area
>in the
>STATIC CSECT - and there is coding needed at startup to move the constants
>into the WSA.
>
>We are not able to move to NORENT due to site conventions.
>
>Now my question: is it sufficient to mark those arrays with the const
>attribute,
>that is
>
>static const double tab [100000] = { ... values follow ... };
>
>or are there special #pragmas needed to prevent this table from being
>moved to the WSA, given the RENT compiler option?
>
Years ago, I investigated such behavior with an ISV compiler, not
IBM's. In that case, yes, if an object was declared const it was not
moved to writable storage area. I looked further at the ANSI
standard which says, IIRC, that if an object is declared const in
one translation unit and declared not const in another translation
unit (of course you would _never_ do that), and the latter modifies
the object, the result is undefined. It stated no restriction if the
object is never modified. I concluded that the ISV compiler might
be stretching the standard by allowing the two translation units to
refer to different instances of the object. I didn't press the point.
But an object declared static shouldn't be accessible by name
from more than one translation unit.
-- gil
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