Undesired reserved space

[0xfede7c8]

Hi, first of all, thank you very much for the work. It is very useful and professional.

Now, the "issue" I had is the following. Maybe I'm doing something wrong but, I don't know why I have this padding created on the .h file.

The RDL is a simple file:

regfile regfile1 {
  default regwidth = 32;

  reg {field {} field1reg1;} reg1;

  reg {field {} field1reg2;} reg2;
};

addrmap test2_regmap {
    default regwidth = 32;
    
    reg {field {} field1reg3;} reg3;

    regfile1 regf;
};

And I run peakrdl with:

peakrdl c-header test2_regmap.rdl -o out.h

I'm getting the .h:

....
// Addrmap - test2_regmap
typedef struct __attribute__ ((__packed__)) {
    uint32_t reg3;
    uint8_t RESERVED_4_7[0x4];
    regfile1_t regf;
} test2_regmap_t;
...

I don't know why there is a reserved array of chars. I think it is aligned to 32bits.

Do you know what may be happening? Any recommendations appreciated.

[0xfede7c8]

Update:

I checked the code where this padding is added:

https://github.com/SystemRDL/PeakRDL-cheader/blob/main/src/peakrdl_cheader/header_generator.py#L275

#...
padding = child.raw_address_offset - current_offset
if padding:
    self.write_byte_padding(current_offset, padding)
    current_offset += padding
#...

Basically this is saying that if the child's (current node) max offset (the size of the child basically) is bigger than the current offset (the current position in the addrmap) a padding will be added to match the maximum of the child.

It's fun because if I include a bunch of registers as a regfile, the child.raw_address_offset is bigger than if I add the registers to the regmap "manually" (this means not using a regfile). In that last case each register will be processed manually, where the child.raw_address_offset is always smaller than the current_offset so no padding is needed.

Example:

regfile regfile1 {
  default regwidth = 32;

  reg {field {} field1reg1;} reg1;

  reg {field {} field1reg2;} reg2;
};

addrmap test2_regmap {
    default regwidth = 32;
    
    reg {field {} field1reg3;} reg3;

    regfile1 regf;
};

This creates padding.

addrmap test2_regmap {
    default regwidth = 32;
    
    reg {field {} field1reg3;} reg3;
    
   reg {field {} field1reg1;} reg1;
   reg {field {} field1reg2;} reg2;
};

This doesn't.

Am I missing something here?

I would understand this logic a bit more if we were creating a C union but we are talking about structs here.
Every hing would be appreciated.