ESP32 Forum

Posted: **Tue Apr 04, 2017 11:49 am**

Hi,

My goal is to make a component that read from some sensors. Due to the requirements of the project, the code must be in C++ cause I need to use some pattern design, but the project(Main and other components, should be write with C).

file1.c-----Calls static function---->file2..cpp-----Create an A class----->A

when I try to compile, it simply doesn't work. The .cpp(file2) is not C++ code. And when I try to include into file2 class A, it says that it doesn't find the file(I Tripled check that its ok). #ifdef __cplusplus macro is not defined.

Inside the .mk files I have defined the:
COMPONENT_ADD_LDFLAGS=-lstdc++ -l$(COMPONENT_NAME)

It can not even include <string>, it says that it doesn't find the file.

What am I missing?

Thanks for the support!

Posted: **Tue Apr 04, 2017 1:36 pm**

ervays wrote:Hi,

My goal is to make a component that read from some sensors. Due to the requirements of the project, the code must be in C++ cause I need to use some pattern design, but the project(Main and other components, should be write with C).

file1.c-----Calls static function---->file2..cpp-----Create an A class----->A

when I try to compile, it simply doesn't work. The .cpp(file2) is not C++ code. And when I try to include into file2 class A, it says that it doesn't find the file(I Tripled check that its ok). #ifdef __cplusplus macro is not defined.

Inside the .mk files I have defined the:
COMPONENT_ADD_LDFLAGS=-lstdc++ -l$(COMPONENT_NAME)

It can not even include <string>, it says that it doesn't find the file.

What am I missing?

Thanks for the support!

Just because it's not C++ code, if you're putting it in a .cpp file, you're subjected to the C++ rules for everything, including name mangling.

Unless you tell it otherwise, the C++ compiler (which is what you're using with a .cpp per normal makefile or SCons rules (presuming you're using PlatformIO there...) is presuming it is ALL C++ (C code within C++ is simply viewed as classless C++ code with all the rules that apply, including Name Mangling) and name mangling your code so that the linker can't find the references the C compiler makes within your block of code.

Bracket the .h file's for file2.cpp's definitions with an 'extern "C" { }' block for all C functions you're defining and make sure that that .h file is the first thing you include in file2.cpp. At the minimum, this should work right. Failing that, bracket the C functions and variables you're referencing in the .cpp file with the same in the .cpp file. This will turn name mangling off for those functions and variables.

Posted: **Wed Apr 05, 2017 1:44 pm**

Thats not the problem I think. I've test the code in a simple C++ app and it works.

I think that there is smth about the environment cause __cplusplus is not defined.

SensorTask.c

Code: Select all

#include "../Task/SensorsTask.h"
#include "../Controller/SensorsController_Wrapper.h"


static xTaskHandle Sensors_Readings_task_hdl;


/**
 * This function is gonna be the one that handle all the request from other task asking for sensor readings
 */
void sensorsReadingsTask(void *pvParameters)
{

	while(1){



	}
	vTaskDelete(Sensors_Readings_task_hdl);

}




void sensors_Readings_Init() {


	ESP_LOGI("Sensors", "Initializing Sensor_Readings Task");

	struct SensorsController* c = newSensorsController();
	deleteSensorsController(c);

	/* Start BT configuration task*/
	xTaskCreate(sensorsReadingsTask, "SensorReadings Task", 8192, NULL, 5,&Sensors_Readings_task_hdl);





}

SensorsController.h

Code: Select all

#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "esp_log.h"



class SensorsController {
public:
	SensorsController();
	virtual ~SensorsController();
};

SensorsController.cpp

Code: Select all

SensorsController::SensorsController() {

	ESP_LOGI("GasSensorsController", "*******************SIIIIIIIIIIIIIIIIIIIIII***************");
}

SensorsController::~SensorsController() {
	// TODO Auto-generated destructor stub
}

SensorsController_Wrapper.h

Code: Select all

#ifdef __cplusplus
extern "C" {
#endif


typedef struct SensorsController SensorsController;

SensorsController* newSensorsController();



void deleteSensorsController(SensorsController* v);






#ifdef __cplusplus
}
#endif

SensorsController_Wrapper.cc

Code: Select all

#include "SensorsController.h"
#include "SensorsController_Wrapper.h"





extern "C" {
        SensorsController* newSensorsController() {
                return new SensorsController();
        }
        void deleteSensorsController(SensorsController* v) {
                delete v;
        }
}

The problem is that there is no function called newSensorsController or deleteSensorsController. More precisely this is the error:

Code: Select all

$ make -j8
CC src/Task/SensorsTask.o
AR libSensorsReadings.a
LD app-template.elf
.../build/SensorsReadings\libSensorsReadings.a(SensorsTask.o):(.literal.sensors_Readings_Init+0x18): undefined reference to `newSensorsController'
...SensorsReadings\libSensorsReadings.a(SensorsTask.o):(.literal.sensors_Readings_Init+0x1c): undefined reference to `deleteSensorsController'
.../SensorsReadings\libSensorsReadings.a(SensorsTask.o): In function `sensors_Readings_Init':
.../SensorsReadings/src/Task/SensorsTask.c:41: undefined reference to `newSensorsController'
.../components/SensorsReadings/src/Task/SensorsTask.c:42: undefined reference to `deleteSensorsController'
collect2.exe: error: ld returned 1 exit status
make: *** [.../project.mk:323: ..../build/app-template.elf] Error 1

And that's should be smth about cplusplus or the includes(mk files or smth)

Posted: **Wed Apr 05, 2017 5:35 pm**

I think the SensorsController_Wrapper.cc file doesn't get compiled at all. ESP-IDF build system assumes .c extension for C source files and .cpp for C++ source files. You can explicitly list the source files for the given component if you'd like, please see the build system documentation for that.

Posted: **Thu Apr 06, 2017 3:48 am**

Yes, it was the .cc extension.

Thanks for evrthng. This was really frustrating. I'm sort of newby chip programmer, I'm used to plain C++ development.

Cheers!

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