Issues defining a new command.

[jazbaatbadalgaye]

I am trying to write a new M810 command to display an array. Here is what I did

1. Declared a function which returns a pointer to an array.

//In reprap.h 
uint8_t *Gen() noexcept;
uint8_t* my_pointer = Gen();

2. Definition of the function

//in reprap.cpp
uint8_t *RepRap::Gen() noexcept
{
	uint8_t arr[3]={5};
	return arr;
}
 

3. Declared the new Gcode function

//in GCodes.h
void GetData(const StringRef& reply) noexcept;

4. Definition of the new Gcode

//in GCodes.cpp
void GCodes::GetData(const StringRef& reply) noexcept
{
     for (size_t c=0; c<3;c++)
	{
		reply.catf("Arr:  %u" PRIu8 "\n", reprap.my_pointer[c]);
	}	
}

5. Added M810

//in GCodes2.cpp
case 810:
    GetData(reply);
    break;

But when I send M810 on YAT, I get gibberish values like

Arr:  0hhu<LF>Arr:  0hhu<LF>Arr:  2hhu<LF>

What am I doing wrong?

Edit : Fixed it by declaring the

uint8_t arr[3]={5};

as

static uint8_t arr

[oliof]

I think you're not dereferencing your pointer correctly?

[dc42]

@jazbaatbadalgaye function Gen returns a pointer to data in local storage that ceases to exist when the function returns.

[jazbaatbadalgaye]

@dc42 Thanks! I fixed it by declaring the arr as static

[zapta]

@dc42 said in Issues defining a new command.:

function Gen returns a pointer to data in local storage

Some compiler flag this out

https://docs.microsoft.com/en-us/cpp/error-messages/compiler-warnings/compiler-warning-level-1-c4172?view=msvc-160