Problem with compiling C++ code for nRF52820

[db_lw]

Hi,

I tried to build the ble_app_uart example for nRF52820/s140. In my project I need to use C++ modules.

My usual approach that worked so far:

• Take an example project
• Rename the main.c to main.cpp
• Replace line 381-385
  

  ble_gap_phys_t const phys =
  {
      .tx_phys = BLE_GAP_PHY_AUTO,
      .rx_phys = BLE_GAP_PHY_AUTO,
  };

• Compile with -std=gnu+11.

Oddly this doesn't work with the nRF52820 example and I always get the following error when compiling.

In file included from ../nrf5_sdk/modules/nrfx/mdk/nrf.h:192,
                 from D:\Development\wDALI2_BT_Switch\wdali-2-bt-button\firmware\ble_app_uart_pca10100e_s140\main.cpp:55:
../nrf5_sdk/modules/nrfx/mdk/compiler_abstraction.h:193:60: error: expected constructor, destructor, or type conversion before '(' token
../nrf5_sdk/modules/nrfx/mdk/compiler_abstraction.h:232:5: note: in expansion of macro 'NRF_STATIC_ASSERT'
../nrf5_sdk/modules/nrfx/mdk/nrf_erratas.h:48:1: note: in expansion of macro 'NRF_MDK_VERSION_ASSERT_AT_LEAST'

When I do the same thing with the ble_app_uart example for nRF52840/s140 it compiles just fine with C++.

Does anyone have an idea how to fix this problem and why it only occurs when compiling for nRF52820?

Thanks in advance.

[db_lw]

I was able to trace the problem down to the header file nrf_gpio.h. It seems like it doesn't build with C++ for nRF52820 because of the include in line 65. But I'm not sure how to solve this properly.

#if defined(NRF52820_XXAA)
#include <nrf_erratas.h>
#endif

[Edvin]

Hello,

Please search for

extern "C"

In your project. See how some files have this:

    #ifdef __cplusplus
         }  /* extern "C" */
      }  /* namespace std */
    #endif /* __cplusplus */
    
    
    
    ...
    
    
    #ifdef __cplusplus
    #ifndef __STDARG_NO_EXPORTS
      using ::std::va_list;
    #endif
  #endif /* __cplusplus */

Try to include that in nrf_erratas.h.

Best regards,

Edvin

[Edvin]

Can you try to comment out some lines in nrf_erratas.h to see whether it is one of the lines or one of the files from there that your compiler doesn't like? It may look like it is from compiler_abstraction.h. Perhaps you can try to add the cplusplus guart in that file as well. 

[Edvin]

db_lw said:

Replace line 381-385

 Those are the original lines. (except tx and rx is swapped). Are you sure you started with a clean example?

Line 378 - 387 from the original main.c file:

        case BLE_GAP_EVT_PHY_UPDATE_REQUEST:
        {
            NRF_LOG_DEBUG("PHY update request.");
            ble_gap_phys_t const phys =
            {
                .rx_phys = BLE_GAP_PHY_AUTO,
                .tx_phys = BLE_GAP_PHY_AUTO,
            };
            err_code = sd_ble_gap_phy_update(p_ble_evt->evt.gap_evt.conn_handle, &phys);
            APP_ERROR_CHECK(err_code);

[db_lw]

I have added the extern C part to compiler_abstraction.h but it is still not working.

Those are the three files I made changes to, to make it work with C++:

2475.main.cpp

compiler_abstraction.h

6278.nrf_erratas.h

[Edvin]

I still don't have the setup (IDE settings and so on) to replicate this. Is there any additional modifications from the SDK, apart from this? The compiler error is a quite generic error that you'll see when you add an '{' or '(' on the wrong place. 

The fact that you mentioned the lines:

ble_gap_phys_t const phys =
{
    .tx_phys = BLE_GAP_PHY_AUTO,
    .rx_phys = BLE_GAP_PHY_AUTO,
};

Which are identical to the original example makes me wonder whether this comes from a clean SDK, or if someone else has handed you the SDK. Perhaps they already did some changes to make it compile for the other boards?

BR,

Edvin

[db_lw]

I fixed the problem by replacing lines 192-198 with this code:

#ifndef NRF_STATIC_ASSERT
    #ifdef __cplusplus
    #define NRF_STATIC_ASSERT(cond, msg) extern char (*_do_assert(void)) [sizeof(char[1 - 2*!(cond)])]
    #else
    #define NRF_STATIC_ASSERT(cond, msg) _Static_assert(cond, msg)
    #endif
#endif

Something similar is done in app_util.h of nRF5 SDK 17.0.2.

Thanks Edvin for your help!