Am 01.04.2014 00:11, schrieb Steve Comstock:
On 3/31/2014 4:02 PM, Bernd Oppolzer wrote:
We discussed this further with some co-workers on my customers site.
There are some more aspects of this discussion:
a) the C language manual at one certain point states what are pointers
acceptable
to C and what are not. From the wording there it sounds as if pointers
that come
from parameters from other languages (not C) were not acceptable to C -
only
addresses resulting from parameters from other C functions !!! If this
is true ...
how do I do inter-language calls between PL/1 and C successfully?
Ahem.
http://www.trainersfriend.com/Language_Environment_courses/m520descr.htm
-Steve Comstock
How do you solve the problem that a pointer coming from a PL/1 module
(or ASSEMBLER) and possibly having the high order bit on is not accepted
from the C module as a valid pointer and that the results, if you use
this pointer,
are "unpredictable" or "undefined", as stated by the C manuals? And:
if you try to clean the first bit of this pointer by casting it to an
unsigned int
and switching the bit off, then you get this logic removed from the
object code
by the optimizer, because the optimizer (of the C compiler) THINKS that a
C pointer never has the high order bit set, so there is no need to execute
this logic?
In the past, we were able to clean the first bit, because the logic was NOT
removed, but from the compiler error we faced in the last few days it seems
that now the C compiler (at OPT(2)) believes that all pointers are
limited to
31 bit and that logic dealing with the high order bit is unnecessary and
can
therefore be removed ...
Kind regards
Bernd
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