segmentation fault, it's big problem to me

[rgmmelo]

hello, I'm trying to write a source in c, but I've a big problem. when i write my code
like this:

#include <stdio.h>
#include "lfixo.h"
 
extern long int a,m;
extern float nad[7];
 
float Tgl0 = 580;
float Tr0 = 590;
 
void ci(float **Tgl,float **Ts,float **Tr)
{
Tgl = Alocar(a,m);Ts = Alocar(a,m);Tr = Alocar(a,m);
long int i,j,k;
 
for(j=0;j<m;j++)
{
// inicialização das temperaturas
 
Tgl[0][j]=Tgl0;
 
//condições iniciais de temperatura na fase fluida
Ts[0][j]=Tgl0; //condições iniciais de temperatura na fase sólida
Tr[0][j]=Tr0; //condições iniciais de temperatura na fluido refrigerante
 
 
Liberar(a,m,Tgl);Liberar(a,m,Ts);Liberar(a,m,Tr);}
 
 
 

where is Alocar and Liberar are function to alocate and release memory for may 2d matrix.
and the main function are:

#include <stdio.h>
#include "lfixo.h"
long int a=2400,m=6;
float nad[7],dt;
 
void main(void)
 
{
float **Tgl, **Ts, **Tr;
 
ci(Tgl,Ts,Tr);
}
 

thus, my program works. but if put any change(considering the same main function) as the follow(The line 30 is the difference between 2 codes ):

 
#include <stdio.h>
#include "lfixo.h"
 
extern long int a,m;
extern float nad[7];
 
float Tgl0 = 580;
float Tr0 = 590;
 
void ci(float **Tgl,float **Ts,float **Tr)
{
Tgl = Alocar(a,m);Ts = Alocar(a,m);Tr = Alocar(a,m);
long int i,j,k;
 
 
for(j=0;j<m;j++)
{
// inicialização das temperaturas
 
Tgl[0][j]=Tgl0;
 
//condições iniciais de temperatura na fase fluida
Ts[0][j]=Tgl0; //condições iniciais de temperatura na fase sólida
Tr[0][j]=Tr0; //condições iniciais de temperatura na fluido refrigerante
}
for(k=0;k<a;k++){
for (j=1;j<=m-1;j++) {
//   nós internos
// the line below is cause of my problem       Tgl[k+1][j]=Tgl[k][j]*(1-2*nad[1]-nad[2]-nad[3])+Tgl[k][j-1]*(nad[0]+nad[1])+Tgl[k][j+1]*(-nad[0]+nad[1])+nad[2]*Ts[k][j]+nad[3]*Tr[k][j];
 
  }
}
 
Liberar(a,m,Tgl);Liberar(a,m,Ts);Liberar(a,m,Tr);}
 

my code doesn't work well, for example, if set a=240(in main function), the loop goes up to a=226. then if set a=226 the loop run until a=200(or something like this). and now what I have to do?what or where is the problem?

[weaknessforcats]

void ci(float **Tgl,float **Ts,float **Tr) <<<<<<<<<<<<<<<<<<<<<
{
Tgl = Alocar(a,m);Ts = Alocar(a,m);Tr = Alocar(a,m);
long int i,j,k;

void main(void)

{
float **Tgl, **Ts, **Tr;

ci(Tgl,Ts,Tr); <<<<<<<<<<<<<<<<<<<<<<<
}

I'm not sure what you are doing here. ci() takes float** argiments. Your main() passes float** variables. The problem is that the Tgl, Ts and Tr in the function are copies of the Tgl, Ts and Tr variables used on the call. At the end of ci(), these copies will be destroyed. The net effect is nothing comes out of your function and the variables in main() never do get initialized. If main() continues, you will crash shortly.

Normally in a case like this, ou declare pointers in main() and pass the addresses to the function. The function now had the address of the pointer so it can dereference this address to update the address in the pointer used on the call.

void MyFunction(float** arg)
{
    *arg = malloc(sizeof(float));
}
 
int main()
{
    float* result;
    MyFunction(&result);
}
 

Maybe you can clear this up before I look at your other main().