c++ array initialization on nRF9160

[WhiteCloud2]

Hi, 

I have a C++ array or structure initialization issue that only occurs on nRF9160, but not other devices.

I am looking at the possibility of using JEDI in our IoT devices. On other devices, it runs without issues. On nRF9160, I used the mqtt_simple example as a starting point and wrote some test code to exercise JEDI features. Right at the beginning, it does not produce the expected results. I spent a few days tracking it down and eventually discovered at least one of the problem is about C++ array of structure initializations.

I have a 4-level nested structure. Each level is actually the same 48 bytes wrapped in the structure next level up. The issue is when the structure is initialized and declared as a scalar value, it is correctly initialized with the provided values. However, when it is declared as a single element array, all 48 bytes become zeros, as shown below. 

Has anyone experienced similar issues? What am I missing? What compiler flags, options, etc could lead to such a problem? Appreciate any comments and help.

The test project is attached below.

Device: nRF9160-DK

nRF Connect 3.6.1

nRF Connect SDK v1.7.1

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#include <stdint.h>

#include <stdio.h>

#include <string.h>

#include <stdlib.h>

#include "bls12_381/fq.hpp"

static constexpr embedded_pairing::bls12_381::Fq scalar = {

{{{.std_words = {0x1c7238e5, 0xcf1c38e3, 0x786f0c70, 0x1616ec6e, 0x3a6691ae, 0x21537e29,

0x4d9e82ef, 0xa628f1cb, 0x2e5a7ddf, 0xa68a205b, 0x47085aba, 0xcd91de45}}}}

};

static constexpr embedded_pairing::bls12_381::Fq array[1] = {

{{{{.std_words = {0x1c7238e5, 0xcf1c38e3, 0x786f0c70, 0x1616ec6e, 0x3a6691ae, 0x21537e29,

0x4d9e82ef, 0xa628f1cb, 0x2e5a7ddf, 0xa68a205b, 0x47085aba, 0xcd91de45}}}}}

};

void print_struct(const char *title, const uint8_t *cbuf, int len)

{

printf("\n");

printf("[%s] %d\n", title, len);

XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

#include <stdint.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>

#include "bls12_381/fq.hpp"

static constexpr embedded_pairing::bls12_381::Fq scalar = {
        {{{.std_words = {0x1c7238e5, 0xcf1c38e3, 0x786f0c70, 0x1616ec6e, 0x3a6691ae, 0x21537e29, 
                         0x4d9e82ef, 0xa628f1cb, 0x2e5a7ddf, 0xa68a205b, 0x47085aba, 0xcd91de45}}}}
};

static constexpr embedded_pairing::bls12_381::Fq array[1] = {
        {{{{.std_words = {0x1c7238e5, 0xcf1c38e3, 0x786f0c70, 0x1616ec6e, 0x3a6691ae, 0x21537e29, 
                          0x4d9e82ef, 0xa628f1cb, 0x2e5a7ddf, 0xa68a205b, 0x47085aba, 0xcd91de45}}}}}
};

void print_struct(const char *title, const uint8_t *cbuf, int len)
{
    printf("\n");
    printf("[%s] %d\n", title, len);
    for (int i = 0; i < len; i++) {
        if (i % 30 == 0 && i != 0)
            printf("\n");
        else if ((i % 10 == 0 || i % 20 == 0) && i != 0)
            printf("  ");
        printf("%02X ", cbuf[i]);
    }
    printf("\n");
}

void run_tests() 
{
    print_struct("scalar", (const uint8_t *) &scalar, sizeof(scalar));
    print_struct("array", (const uint8_t *) &array[0], sizeof(array[0]));
}

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[scalar] 48

E5 38 72 1C E3 38 1C CF 70 0C 6F 78 6E EC 16 16 AE 91 66 3A 29 7E 53 21 EF 82 9E 4D CB F1

28 A6 DF 7D 5A 2E 5B 20 8A A6 BA 5A 08 47 45 DE 91 CD

[array] 48

00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

[scalar] 48
E5 38 72 1C E3 38 1C CF 70 0C   6F 78 6E EC 16 16 AE 91 66 3A   29 7E 53 21 EF 82 9E 4D CB F1
28 A6 DF 7D 5A 2E 5B 20 8A A6   BA 5A 08 47 45 DE 91 CD

[array] 48
00 00 00 00 00 00 00 00 00 00   00 00 00 00 00 00 00 00 00 00   00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00   00 00 00 00 00 00 00 00

array_init.zip