From: robert_s_quinn@yahoo.com (Robert Quinn)
Subject: pragma pack in external packages
Date: 25 Apr 2002 09:49:29 -0700
Date: 2002-04-25T16:49:29+00:00 [thread overview]
Message-ID: <db500a4f.0204250849.61c0791e@posting.google.com> (raw)
I'm trying to figure out something about raw storage. I just
installed gnat and I'm trying to teach myself to represent bits of
data with Ada, but I hit a snag. Basically I can't seem to "pragma
pack" the data type if I am using the data type in a package OTHER
than the declaration package. e.g.:
Suppose I have an array of bits:
package definitions is
ONE_BIT_TYPE is range 0..1;
for ONE_BIT_TYPE'SIZE use 1
5_BIT_ARRAY_TYPE is array (1..5) of ONE_BIT;
pragma pack (5_BIT_ARRAY_TYPE);
end definitions;
It seems like my 5 bit array should now refer to 5 consecutive bits.
But now if I try to use this array in a record in an external package,
I get an error:
package more_definitions is
type my_record is record
IMPORTANT_5_BIT_ARRAY : definitions.5_BIT_ARRAY_TYPE;
end record
pragma pack(my_record);
for my_record use record
IMPORTANT_5_BIT_ARRAY at 0 range 0 .. 4;
end record;
end more_definitions;
after compile I get:
ERROR: size for IMPORTANT_5_BIT_ARRAY too small, minimum allowed is 40
Note that I don't get this error if I move the record declaration
INTERNAL to the package where the array type is defined. Only when I
use the array type in an external package does the compiler decide I
need a whole BYTE for each BIT of data!
Any ideas?
Thanks,
Robert Quinn
Note that I don't do any low-level programming in my job (is this what
you low level programmers do a lot of?), this is just a hobby.
next reply other threads:[~2002-04-25 16:49 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-04-25 16:49 Robert Quinn [this message]
2002-04-25 19:03 ` pragma pack in external packages Stephen Leake
2002-04-25 19:07 ` Pat Rogers
2002-04-26 1:55 ` Robert Dewar
2002-04-26 1:52 ` Robert Dewar
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