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Newsgroups: comp.lang.ada
Date: Wed, 1 Aug 2018 10:38:05 -0700 (PDT)
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Subject: Variant record memory storage question
From: NiGHTS <nights@unku.us>
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Xref: reader02.eternal-september.org comp.lang.ada:54008
Date: 2018-08-01T10:38:05-07:00
List-Id: <comp.lang.ada>

Say I had a variant record like this:

type Which_One is (Is_Small, Is_Big);

type Variant_Record (Option : Which_One) is 
record
    case Option is
        when Is_Small =>
            Var_1 : Byte -- 1 byte
        when Is_Big =>
            Var_2 : Some_Large_Record -- 1000 bytes
    end case;
end record;

Will the record Variant_Record( Is_Small ) be stored as 1 byte? Or does it act almost like a C union allocating the memory for Variant_Record( Is_Big ) even though it will never morph at run-time?

I am trying to determine the most memory-efficient way to store a complex record and it seems Variant_Record can help me do this, but I am unsure if it will work the way I think it will.

Note I am using gcc. Thank you.