Initialize array of structs - c++

Question

I am trying to initialize an array of struct in C++.

This is my struct:

typedef ap_fixed<16,1> ap_fixed_data_type;
typedef struct {

    ap_fixed_data_type real_part;
    ap_fixed_data_type imaginary_part;

} my_data_struct;

And this is my array of structs:

static my_data_struct IFFT_output[1024];

I would like to initialize my array of struct using (if possible) the same "syntax" of standard arrays, as an example:

int my_array[1024] = {0};

This will initialize my array to all 0.

What I am trying to achieve is something like:

static my_data_struct IFFT_output[1024]={{0,0}};

Where this code should initialize each field (real_part and imaginary_part) in each struct to 0. With the above code I get this error:

terminate called after throwing an instance of '__gnu_cxx::recursive_init_error'

Which seems to be caused by bad initialized static variable (like here).

I know that I could initialize my data with a simple for loop, but I wanted to do something more "compact".

Is there a way to initialize my array of struct with the "syntax" I showed above?

My bad, typo. Fixed

Mattia Surricchio
– Mattia Surricchio

2021-06-25 15:36:53 +00:00
Commented Jun 25, 2021 at 15:36 — Mattia Surricchio
– Mattia Surricchio, Commented Jun 25, 2021 at 15:36

Mircea Ispas · Accepted Answer · 2021-06-25 15:41:44Z

4

This looks like C to me. If you want to use C++ you can have:

using ap_fixed_data_type = ap_fixed<16,1>;
struct my_data_struct
{
    my_data_struct()
        : real_part(/*initialization code here*/)
        , imaginary_part(/*initialization code here*/)
    {
    // more initialization code here
    }
    ap_fixed_data_type real_part;
    ap_fixed_data_type imaginary_part;

};

std::vector<my_data_struct> vec(1024);
std::array<my_data_struct, 1024> array;

edited Jun 25, 2021 at 15:41

answered Jun 25, 2021 at 15:34

Mircea Ispas

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8 Comments

YSC Over a year ago

Suggestion: my_data_struct() : real_part{0}, imaginary_part{0} {} if ap_fixed doesn't have a default constructor.

Mattia Surricchio Over a year ago

The environment i am working with accept c++, I wrote the code in that way because it seemed the simplest way to do what I needed. Is there a way to initialize my array with the syntax i showed? Still a very useful answer

Mircea Ispas Over a year ago

@MattiaSurricchio there is no performance benefit on using static my_data_struct IFFT_output[1024]; over std::array<my_data_struct, 1024> IFFT_output;, you just lose safety. The absence of constructors is also error prone. If you have a C++ compiler I don't see any benefit to write C code

Mattia Surricchio Over a year ago

This code is part of a bigger one that is meant to be synthesized and run on hardware, the easier/lower - level, the better. The static keyword is needed since it is a register which needs to be stored in memory

Mircea Ispas Over a year ago

Those are just example on how to use multiple elements of type my_data_struct. std::vector uses dynamic memory allocation which is useful when you don't know the size in advance and std::array is basically a C style array with extra safety and features.

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