To make it clear:
* scp1215ein in1215 = { 0 };
ST r6,<a5:d272:l4>(,r13,272)
MVI <a5:d276:l1>(r13,276),0
* scp1215aus out1215 = { 0 };
ST r6,<a5:d296:l4>(,r13,296)
MVI <a5:d300:l1>(r13,300),0
The ST operations initialize the first components of the structures,
which are fullwords. This is what should be done, according to
the IBM C language reference.
The rest of the structures should remain unchanged (uninitialized),
according to IBM's language reference, and should be set to zero,
according to ANSI C language reference. The structure out1215,
for example, is 24 bytes long.
Now the MVI makes absolutely no sense to me.
It would only make some sense, if it was followed by an overlapped MVC
instruction, which would set the rest of the structure to zero. But such a
instruction is not generated by the compiler.
???
Kind regards
Bernd
Bernd Oppolzer schrieb:
Hello all,
sorry for asking this question on IBM-Main, but the C370 list is so
silent
that I doubt that anyone is actually listening.
We observed a sort of problem today which showed up as a 0C4 abend
due to a not proper initialized pointer component of a C structure.
Further examination showed that the structured was initialized as follows
structure_type structure_identified = { 0 };
The structure has several components; the last component is the pointer.
According to the IBM C language reference, only the first component is
initialized to zero, and the other components have random contents,
because the storage class is automatic. The compiler generates only
initialization logic for the first few bytes of the auto structure. So
from this
point of view, everything is right.
But: the ANSI C language reference, for example in the Kernighan Ritchie
book appendix, and most other C language references I found on the web,
clearly state that if the number of initializers on structure
initialization is less
than the number of structure components, the remaining components are
initialized to zero, even for auto structures.
This is not an error in that sense that the compiler does not what is
written
in the language reference, but instead it is a contradiction between
IBM's
language reference and ANSI language reference.
What do you think about this? Does it make sense to complain at IBM
about it? We have hundreds of C programs in production use which use
this kind of initialization (maybe) and now we are afraid that we need to
examine all these programs.
Kind regards
Bernd
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