switch-examples/templates/sysmodule/source/main.c

// Include the most common headers from the C standard library
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

// Include the main libnx system header, for Switch development
#include <switch.h>

// Sysmodules should not use applet*.
u32 __nx_applet_type = AppletType_None;

// Adjust size as needed.
#define INNER_HEAP_SIZE 0x80000
size_t nx_inner_heap_size = INNER_HEAP_SIZE;
char   nx_inner_heap[INNER_HEAP_SIZE];

void __libnx_initheap(void)
{
	void*  addr = nx_inner_heap;
	size_t size = nx_inner_heap_size;

	// Newlib
	extern char* fake_heap_start;
	extern char* fake_heap_end;

	fake_heap_start = (char*)addr;
	fake_heap_end   = (char*)addr + size;
}

// Init/exit services, update as needed.
void __attribute__((weak)) __appInit(void)
{
    Result rc;

    // Initialize default services.
    rc = smInitialize();
    if (R_FAILED(rc))
        fatalSimple(MAKERESULT(Module_Libnx, LibnxError_InitFail_SM));

    // Enable this if you want to use HID.
    /*rc = hidInitialize();
    if (R_FAILED(rc))
        fatalSimple(MAKERESULT(Module_Libnx, LibnxError_InitFail_HID));*/

    //Enable this if you want to use time.
    /*rc = timeInitialize();
    if (R_FAILED(rc))
        fatalSimple(MAKERESULT(Module_Libnx, LibnxError_InitFail_Time));

    __libnx_init_time();*/

    rc = fsInitialize();
    if (R_FAILED(rc))
        fatalSimple(MAKERESULT(Module_Libnx, LibnxError_InitFail_FS));

    fsdevMountSdmc();
}

void __attribute__((weak)) userAppExit(void);

void __attribute__((weak)) __appExit(void)
{
    // Cleanup default services.
    fsdevUnmountAll();
    fsExit();
    //timeExit();//Enable this if you want to use time.
    //hidExit();// Enable this if you want to use HID.
    smExit();
}

// Main program entrypoint
int main(int argc, char* argv[])
{
    // Initialization code can go here.

    // Your code / main loop goes here.
    // If you need threads, you can use threadCreate etc.

    // Deinitialization and resources clean up code can go here.
    return 0;
}