Thread: Pointer becomes NULL inside loop

Hi all,

I'm having a problem with a pointer struct to pointer passed in a function...
We'll, better show first.

Code:

void defCompraBuscaLocal ( int * vCOMP, Instancia * I, Solucao * S, VetDeListas * K, int prod )
{
	Noh * p = 0;
	int i=0, aux=0, aux_DEM=0, qtmcd=0, qtdCOMP=0;
	
	aux_DEM = I->DEM[prod];
	qtmcd = I->merc;

	for(i=0; i<qtmcd; i++) {
		assert(S->binMcd != 0);
		vCOMP[i] = 0;
	}
	
	p = (K->VL[prod])->cab;
	while ( p != 0 )
	{
		if ( S->binMcd[p->dado] > -1 )
		{
			if ( aux_DEM > 0 )
			{
				aux = detMinimo(aux_DEM, I->DISPB[prod*qtmcd+p->dado]);
				vCOMP[p->dado] = aux;
				aux_DEM = aux_DEM - aux;
			}
			else
			{
			    qtdCOMP = somaElemVetor(vCOMP,qtmcd);
			    vCOMP[0] = qtdCOMP;
				return;
			}	
		}	/*if ( S->binMcd[p->dado] == 1 )*/
		p = p->prox;
	}	/*while ( p != 0 )*/
	
    qtdCOMP = somaElemVetor(vCOMP,qtmcd);
    vCOMP[0] = qtdCOMP;    
	
	return;
}

I hope this amount of code will suffice to explain my point: The assertion fails after some loops in the 9th line

Code:

for(i=0; i<qtmcd; i++) {
	assert(S->binMcd != 0);
	vCOMP[i] = 0;
}

The struct S is

Code:

typedef struct Solucao
{
    int fo_total;
    int fo_comp;
    int fo_transp;
    _Bool fac;
    int * binMcd;
    Lista * sol;
    int * COMP;
} Solucao;

Running GDB I get

Code:

Breakpoint 1, defCompraBuscaLocal (vCOMP=0x61e010, I=0x609910, S=0x61e030, K=0x6096d0, prod=6)
    at heur_const_atpp.c:148
148		Noh * p = 0;
(gdb) break 155
Ponto de parada 2 at 0x403b94: file heur_const_atpp.c, line 155.
(gdb) continue 
Continuing.

Breakpoint 2, defCompraBuscaLocal (vCOMP=0x61e010, I=0x609910, S=0x61e030, K=0x6096d0, prod=6)
    at heur_const_atpp.c:155
155		for(i=0; i<qtmcd; i++) {
(gdb) print S->binMcd 
$1 = (int *) 0x6207a0
(gdb) print S->COMP 
$2 = (int *) 0x61e080
(gdb) print *S->binMcd 
$3 = 13
(gdb) next
156		  assert(S->binMcd != 0);
(gdb) 
157			vCOMP[i] = 0;
(gdb) 
155		for(i=0; i<qtmcd; i++) {
(gdb) 
156		  assert(S->binMcd != 0);
(gdb) 
157			vCOMP[i] = 0;
(gdb) 
155		for(i=0; i<qtmcd; i++) {
(gdb) 
156		  assert(S->binMcd != 0);
(gdb) 
157			vCOMP[i] = 0;
(gdb) continue 
Continuing.
heur_const_atpp: heur_const_atpp.c:156: defCompraBuscaLocal: Assertion `S->binMcd != 0' failed.
 Rodando ../Clase5-SymCapTPP/CapEuclideo.50.50.1.1.tpp     
Program received signal SIGABRT, Aborted.
0x00007ffff780aa75 in *__GI_raise (sig=<value optimized out>) at ../nptl/sysdeps/unix/sysv/linux/raise.c:64
64	../nptl/sysdeps/unix/sysv/linux/raise.c: Arquivo ou diretório não encontrado.
	in ../nptl/sysdeps/unix/sysv/linux/raise.c

Translation of the last part 'Arquivo ou diretório não encontrado'='file or directory not found'.

I did some checking and found out that S is not NULL after the assertion, but S->COMP and S->binMcd are.

If anyone can point a direction I would be very thankful.

Thanks a lot,
Abel

Thank you for the effort, and sorry to waste your time. I found what happened (though I haven't found where it happen yet).

The vector vCOMP was pointing to right before where S where pointing to. When I did the for, it set all vector in S to 0, hence NULLifying them.

Since the vector vCOMP was allocated before, I don't know what is going wrong. But knowing the error is very useful.

Thank you everyone, this thread can be closed.

Abel