Valgrind Block are Lost - c

Question

I'm trying to understand why the follow code is wrong using valgrind. The problem apparently is in the function destroy_poli, I say this because when I comment this part of the main function
poli ** p = (poli **) malloc( sizeof( poli *) * npols );
for(k=0;k<npols;k++) {
p[k] = new_poli( nvars, w );
}
for(k=0;k<npols;k++)
destroy_poli(p[k]);
free(p);
I get 0 errors with valgrind. Please Could you help to undersantd where my error is?
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "bits.h"
#include "parsemap.h"
#include "galois.h"
#define ANF 1
#define pos(i,j) (((1+i)*i)/2 + j)
int *table_red;
typedef struct _mono {
int w;
char ** v;
} mono;
typedef struct _poli {
int nvars;
mono ** p;
} poli;
void destroy_mono(mono * m){
int i=0;
for(i=0;i<2*(m->w);i++)
free(m->v[i]);
free(m->v);
}
void destroy_poli(poli * p){
int nvars = p->nvars;
int i;
for(i=0;i<((nvars+1)*nvars)/2;i++)
destroy_mono(p->p[i]);
free(p->p);
}
mono * new_mono( int w, int idx ) {
int i;
mono * r = (mono *) malloc( sizeof(mono) );
r->w = w;
r->v = (char **) malloc( sizeof(char *)*( 2*w ) );
for( i = 0; i < 2*w; i++ ) {
r->v[i] = (char *) malloc( sizeof(char )*( 4096 ) );
r->v[i][0] = 0;
}
return r;
}
poli * new_poli( int nvars, int w ) {
poli * p = (poli *) malloc( sizeof(poli) );
p->nvars = nvars;
int i,j;
nvars++;
p->p = (mono **) malloc( sizeof( mono * ) * ((nvars+1)*nvars)/2);
nvars--;
for(i=0; i < nvars; i++ )
for(j=0; j <=i; j++ )
p->p[pos(i,j)] = new_mono( w, i );
}
return p;
}
void create_table( int w ) {
table_red = (int *) malloc( sizeof( int ) * 2 * w );
int i, j, a, b;
for(i=0;i<2*w;i++) {
table_red[i] = mod( (1 << i), w );
}
}
int ** read_input( int * npols, int * nvars, int * w, int ** enc ) {
int i, j;
*npols = 1;
*nvars = 1;
int nv = *nvars + 1;
int np = *npols;
*enc = (int *) malloc( sizeof( int) * np );
for(i=0; i < np; i++ ) {
(*enc)[i] = 0;
}
int ** coefs = (int **) malloc( sizeof( int *) * np );
for(i=0; i < np; i++ ) {
coefs[i] = (int *) malloc( sizeof( int) * ((nv+1)*nv)/2 );
for(j=0; j < ((nv+1)*nv)/2; j++)
coefs[i][j] = 0;
}
return coefs;
}
int main(int argc, char ** argv) {
int nvars;
int npols;
int i;
int w = 2, *enc;
int ** coefs = read_input( &npols, &nvars, &w, &enc );
int k, j;
create_table( w );
npols = 1;
poli ** p = (poli **) malloc( sizeof( poli *) * npols );
for(k=0;k<npols;k++) {
p[k] = new_poli( nvars, w );
}
for(k=0;k<npols;k++)
destroy_poli(p[k]);
free(p);
for(i=0; i < npols; i++ )
free(coefs[i]);
free(coefs);
free(enc);
return 0;
}
==24066== 16 bytes in 1 blocks are definitely lost in loss record 2 of 3
==24066== at 0x4C2AB80: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==24066== by 0x400CE8: new_poli (in /home/grados-sanchez/workspace/mq2sat/mq2sat/mq2sat)
==24066== by 0x400FD7: main (in /home/grados-sanchez/workspace/mq2sat/mq2sat/mq2sat)
==24066==
==24066== 16 bytes in 1 blocks are definitely lost in loss record 3 of 3
==24066== at 0x4C2AB80: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==24066== by 0x400C46: new_mono (in /home/grados-sanchez/workspace/mq2sat/mq2sat/mq2sat)
==24066== by 0x400D70: new_poli (in /home/grados-sanchez/workspace/mq2sat/mq2sat/mq2sat)
==24066== by 0x400FD7: main (in /home/grados-sanchez/workspace/mq2sat/mq2sat/mq2sat)
==24066==

Answer 1

You are missing free(p) in destroy_poli() and free(m) in destroy_mono(). I was able to determine that by compiling with -g and using valgrind to check the line nunmber where the leaked pointer was allocated tracking it led me to find the problem. Another thing I did was write the code in a way that it can be debugged and maintained, please check this and tell me whether or not it's worth the effort
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#define ANF 1
#define pos(i, j) (((1 + (i)) * (i)) / 2 + (j))
int *table_red;
typedef struct _mono
{
int w;
char **v;
} mono;
typedef struct _poli
{
int nvars;
mono **p;
} poli;
void
destroy_mono(mono *m)
{
if (m == NULL)
return;
for (int i = 0 ; i < 2 * m->w ; i++)
free(m->v[i]);
free(m->v);
free(m);
}
void
destroy_poli(poli *p)
{
if (p == NULL)
return;
for (int i = 0 ; i < ((p->nvars + 1) * p->nvars) / 2 ; i++)
destroy_mono(p->p[i]);
free(p->p);
free(p);
}
mono *
new_mono(int w, int idx)
{
mono *r;
r = malloc(sizeof(*r));
if (r == NULL)
exit(-1);
r->w = w;
r->v = malloc(2 * w * sizeof(*r->v));
if (r->v == NULL)
exit(-1);
for (int i = 0 ; i < 2 * w ; i++)
{
r->v[i] = malloc(4096);
if (r->v[i] == NULL)
exit(-1);
r->v[i][0] = 0;
}
return r;
}
poli *
new_poli(int nvars, int w)
{
poli *p;
p = malloc(sizeof(*p));
if (p == NULL)
exit(-1);
p->nvars = nvars++;
p->p = malloc(((nvars + 1) * nvars * sizeof(*p->p)) / 2);
if (p->p == NULL)
exit(-1);
nvars -= 1;
for (int i = 0 ; i < nvars ; i++)
{
for (int j = 0 ; j <= i ; j++)
p->p[pos(i, j)] = new_mono(w, i);
}
return p;
}
void
create_table(int w)
{
table_red = malloc(2 * w * sizeof(*table_red));
if (table_red == NULL)
exit(-1);
for (int i = 0 ; i < 2 * w ; i++)
table_red[i] = mod((1 << i), w);
}
int **
read_input(int *npols, int *nvars, int *w, int **enc)
{
int i, j;
int **coefs;
int nv;
int np;
*npols = 1;
*nvars = 1;
nv = *nvars + 1;
np = *npols;
enc[0] = malloc(sizeof(**enc) * np);
if (enc[0] == NULL)
exit(-1);
for (i = 0 ; i < np ; i++)
enc[0][i] = 0;
coefs = malloc(sizeof(*coefs) * np);
if (coefs == NULL)
exit(-1);
for (i = 0 ; i < np ; i++)
{
coefs[i] = malloc(((nv + 1) * nv) / 2 * sizeof(**coefs));
if (coefs[i] == NULL)
exit(-1);
for (j = 0 ; j < ((nv + 1) * nv) / 2 ; j++)
coefs[i][j] = 0;
}
return coefs;
}
int main(int argc, char ** argv)
{
int nvars;
int npols;
int i;
int w;
int *enc;
int **coefs;
int k;
poli **p;
w = 2;
coefs = read_input(&npols, &nvars, &w, &enc);;
create_table(w);
npols = 1;
p = malloc(npols * sizeof(*p));
for (k = 0 ; k < npols ; k++) {
p[k] = new_poli(nvars, w);
}
for (k = 0 ; k < npols ; k++)
destroy_poli(p[k]);
free(p);
for (i = 0 ; i < npols ; i++)
free(coefs[i]);
free(coefs);
free(enc);
return 0;
}