Thread: How to Free All Memory ?

How to Free All Memory ?

Its possible, or only for to all position and clean one by one ?

Well it's not so hard actually, as long as you know what you're doing and don't care about screwing up libc allocator (never tested it though, but I do not see any reason why it should not).
On UNIX you have brk/sbrk call. Calling sbrk with 0 as argument will give you the pointer to the current heap (top/bottom? depending on arch supposedly). So at the start of the program call sbrk(0), then later at some point call sbrk(0) again, calculate the difference and call sbrk(difference).

Anyway, although it's possible, I'd never do it that way in real application.

My Equipment is crazy
I think it not free memory when I Try.

Because, im all alloc and de-alloc, but sometimes it crash.

Example:

Code:

int VcomCmdUser(TCPREADDATA *p)  	// Processa as Entradas Recebidas Pelo Usuário. (Obj. Comunicação
{ 	
	unsigned int iSckMaxBuffer = 128;
	
	if (p->Length >= 4 && p->Length <= iSckMaxBuffer){	// Pelo Menos 4 Caracteres [STX]XX[13][10]
		ProcessaChamado (p->ReadUartChar, p->Length);
		ClearStr (p->ReadUartChar);
	}	
	return 1;  
}

int ProcessaChamado (unsigned char *pPacote, int pLen){
	
	unsigned char *cFuncao;
	unsigned char *cSubFuncao;
	unsigned char *cPacote;
	
	int iPosStart, iPosEnd, iPosTam;
	
	cPacote = malloc (pLen);
	if (cPacote == NULL)
		VcomSendSocket(iUserSocket, "3-ERRO DE ALOCAÇÃO DE MEMÓRIA", 29);	
	else
		//VcomSendSocket(iUserSocket, pPacote, pLen);	
	
	//Separa o Pacote
	iPosStart = strpos (pPacote, cSTX);

	iPosStart++;
	
	iPosEnd = strpos (pPacote, cCR);
	
	iPosTam = iPosEnd - iPosStart;
		
	if((iPosStart >= 0) && (iPosEnd)){
		substring(&pPacote[iPosStart], cPacote, iPosTam);
	
		if(strlen (cPacote) > 0){
						
			substring(&cPacote[0], cFuncao, 2);
			
			if (strcmp (cFuncao, "OP") == 0){								// Recebe Ordem de Pesagem
				substring(&cPacote[3], cSubFuncao, iPosTam - 2);
				OrdemProducao (cSubFuncao);
			}
			else if (strcmp (cFuncao, "OI") == 0){							// Recebe Ordem de Pesagem Item
				substring(&cPacote[2], cSubFuncao, iPosTam - 2);
				OrdemProducaoItem (cSubFuncao);
			}
			else if (strcmp (cFuncao, "OK") == 0){							// Tratamento de Confirmações
				substring(&cPacote[2], cSubFuncao, 2);
				if (strcmp (cSubFuncao, "OP") == 0)	{						// Recebe Confirmação de Ordem de Pesagem
					EnviaPedidoPC ("OISL", 4);		
				}
				else if (strcmp (cSubFuncao, "OI") == 0){					// Recebe Confirmação de Ordem de Pesagem Item
					//if (iItemID == 1){
					lPesoTara = lPeso;
					iPesaItem = 1;
				}
				else if (strcmp (cSubFuncao, "IR") == 0){					// Recebe Confirmação de Entrega de Resposta de Item 
					EnviaPedidoPC ("OISL", 4);
				}
			}
			else if (strcmp (cFuncao, "FI") == 0){							// Recebe Finaliza Item Indicando que Recebeu Todos Itens da OP
					iStepInput0 = 0;
					iItemID = 0;
					iPesaItem = 0;
					EnviaPedidoPC ("OPFI", 4);
					EscreveDisplay ("ORDEM CONCLUIDA.........................", 3);
			}
			else if (strcmp (cFuncao, "ER") == 0){							// Erro do Objeto de Comunicação
				iStepInput0 = 0;
				substring(&cPacote[3], cSubFuncao, iPosTam - 3);
				EscreveDisplay (cSubFuncao, 3);
			}
			else if (strcmp (cFuncao, "CC") == 0){							// Check Connection
				// CheckConnection, Não faz nada.
			}
			else{
				// Pacote Não Identitificado;
			}
		} 
		else { 
			free (cPacote);
			return 0;
		}
	}
	
	free (cPacote);
	
	return 1;
}

in this function, i send a CC (CheckConnection at each 30 s)
when i receive some of CC
the program crash and send a message indicate alloc not sucessfull.

Originally Posted by Elysia

That indicates memory corruption - which a "free all" function would not solve.
Get a debugger and start debugging!

I love debug,

but this not a pc
is a icp-i7188E3

and, use a Serial RS-232 to communicate with a balance
a serial 485 to send text to a led display
socket to communicate with a listen socket software
and Digital I/O

when the program crash
it closed all outputs, and no send a message about the error.

If by free everything, one only needs to free all handles currently owned by the current process or a certain target process, I do not believe that the question is quite as dangerous nor far-fetched as many have made it sound. Perhaps with a little further explanation as to what purpose this would serve may help us better point you in the right direction.

My gut feeling is that you keep running into issues where your program is eating away a great deal of system resources and your solution is to go ahead and deallocate everything. Thus eliminating the leaked memory handles. If this is the case, you probably should find out why you are leaking so much memory. If not, then if you are doing this in the event that malloc() returns NULL and wish to "free all" to hopefully claim memory resources for your own I would say this is an ill-advised application programming strategy. Considering the fact that your user may have important tasks eating up all the memory you can never assume too much about why the user is out of RAM.

-sphynxster.

Very true, some mallocs keep a full table of handles internally though. So its reasonable to say that with a keen enough understanding of the internal data structures used you could theoretically free a handle without knowing what it was. At this point we are no longer talking OS specific, we are talking a specific libc or a specific kernel build. It would be an implimentation so specific it would hardly be worth investigating if the initial issue is indeed a mishandled memory leak. I can only leave it up to sergioms to point us in the direction of what he was trying to do.