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From: DrPi <314@drpi.fr>
Subject: Re: Record initialisation question
Date: Sun, 17 Jan 2021 18:03:29 +0100
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Le 09/01/2021 à 11:46, Dmitry A. Kazakov a écrit :
> On 2021-01-09 10:30, DrPi wrote:
>> Hi,
>>
>> I'm working on a µP BSP. The boot sequence of this µP requires byte 
>> structures located in FLASH memory.
>> For example :
>>
>>     type t_Dcd_Header is record
>>        Tag     : Unsigned_8  := 16#D2#;
>>        Length  : Unsigned_16 := 4;      -- Length in byte of the DCD 
>> structure (this header included)
>>        Version : Unsigned_8  := 16#41#;
>>     end record
>>       with Object_Size => 32,
>>            Bit_Order => System.Low_Order_First;
>>
>>     for t_Dcd_Header use record
>>        Tag     at 0 range  0 .. 7;
>>        Length  at 0 range  8 .. 23;
>>        Version at 0 range 24 .. 31;
>>     end record;
>>
>> The t_Dcd_Header is part of t_Dcd record.
>> The Length field of t_Dcd_Header must contain the length of t_Dcd.
>>
>>     Dcd : constant t_Dcd :=
>>      ( Dcd_Header => ( Length => ???, -- Length of Dcd
>>                        others => <>),
>>        ...
>>      );
>>
>> Is there a way to automatically set Length ?
> 
> t_Dcd'Max_Size_In_Storage_Elements?
> 
I finally had success using Object_Size attribute.

I have to set Object_Size of all records.
I also have to specify the Size of enums.
Then I can use t_Dcd'Object_Size.

I had a very bad surprise : Enums are used in some records. One enum did 
not have the Size specified (8 bits). All was working as if it was not 
present except I had to assign it a value. I had to lower the 
Object_Size and the enum was removed from the result (its value was not 
present in memory mapping). After setting Size => 8 to this enum, all 
went well.