What is the correct way of using classes in main.c

[Chao]

Hi,

I have plenty of embedded code that was written in a mixture of C/C++ with target of NXP processors, now I am going to port it onto STM32 targets, I wrote a mini class OutputPort as a test in CubeIDE:

OutputPort.h:

#include "stm32f767xx.h"

class OutputPort

{

public:

OutputPort(GPIO_TypeDef* gpio, uint16_t gpioPin);

virtual ~OutputPort();

private:

GPIO_TypeDef* gpio;

uint16_t gpioPin;

public:

void Toggle();

void Set();

void Reset();

};

OutputPort.cpp:

#include "OutputPort.h"

#include "stm32f7xx_hal.h"

OutputPort::OutputPort(GPIO_TypeDef* gpio, uint16_t gpioPin)

{

this->gpio = gpio;

this->gpioPin = gpioPin;

}

OutputPort::~OutputPort() { }

void OutputPort::Toggle() { HAL_GPIO_TogglePin(gpio, gpioPin); }

void OutputPort::Set() { HAL_GPIO_WritePin(gpio, gpioPin, GPIO_PIN_RESET); }

void OutputPort::Reset() { HAL_GPIO_WritePin(gpio, gpioPin, GPIO_PIN_SET); }

main.c :

/* USER CODE BEGIN Includes */

#include <OutputPort.h>

/* USER CODE END Includes */

/* USER CODE BEGIN 2 */

Port* Led1 = new Port(GPIOB, GPIO_PIN_0);

/* USER CODE END 2 */

The compiler reports: error: unknown type name 'class'

Then I change the main.c to main.cpp as I did with NXP processor which are also ARM Cortex,

it looks like the compilation is OK, but the linker reports error:

Core/Startup/startup_stm32f767zitx.s:99: undefined reference to `main'

The line 99 of startup_stm32f767zitx.s is a jump instruction (jump to main):

/* Call the application's entry point.*/

bl main

Anyone knows any workaround?

Regards

Chao

[TDK]

Classes don't exist in C. You can rename it to main.cpp, or you can put your code in other.cpp and call it from there.

[Chao]

Thanks.

 I changed the main.c to main.cpp and the linker reports error:

The line 99 of startup_stm32f767zitx.s is a jump instruction (jump to main):

/* Call the application's entry point.*/

bl main

Regards

Chao

[Pavel A.]

@Chao To use C++ successfully, one has to know it )) Just to "have plenty of code" does not count. Find a course?

[TDK]

Put the definition of main within an extern "C" { }.

Or maybe you're not compiling C++ files.

[Chao]

I put an extern "C" { }  in two ways for test:

1. surround the main() { }:

extern "C" {

main()

{

... ...

}

}

2. surround the whole main.cpp except for #include <OutputPort.h> that declares a C++ class

But none of them works.

The following is a build after a clean:

I wonder why the compilation of OutputPort.cpp and main.cpp is absent.

Is it possible that something is incorrect in toolset setting?

In NXP's IDE, I got this after I have made a change in main.cpp:

and the following are the contents of main.cpp in my NXP project:

#include "PE_Types.h"

#include "PlcManager.h"

int main(void)

{

  PE_low_level_init();

  PlcManager *plcManager = new PlcManager();

  while (true)    {   plcManager->Run();   }

}

Regards

Chao

[TDK · Accepted solution]

It's not compiling C++ files. Right click project in Project Explorer, select Convert to C++.

[Chao]

Great!

It works now, g++ is used at last.

The current method is to call MyMain() function that is in MyMain.cpp instantiating classes.

Thank you so much

Chao

[Chao]

The current method is to call MyMain() function in main.c, and the MyMain() function is in MyMain.cpp that instantiates classes.

[Andrew Neil]

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