Thread: dynamic allocation from 1 instead of zero

Right; writing on a forum gets me quite distracted apparently!

thanks for spotting them out.
It should work now; I will post something if I get errors in compilations

Thank you again
cfd

Hi again,

I unfortunately get a BUS error with the function that I posted.
I then tried to modify it by making it a pointer to function since I need to return the matrix that I want to allocate, and instead of a BUS error, I now get a segmentation fault

what could that be?

thank you in advance
best,

Code:

int **iarray2d(size_t nrows, size_t ncols, int index)
{
	//nrows = number of rows
	//ncols = ncolumns
	//index = 1 if you want allocation in the fortran way starting from 1
	//index = 0 if you want the standard C allocation way starting from 0
	
	long i;
	int **mat;

	//Malloc pointers to rows
	mat= malloc((nrows+index+1)*sizeof(int*));
	if (!mat){
		printf("Matrix MAT could not be allocted");
		exit(1);
	}
	
	mat[0] = NULL;

	for(i=index; i<nrows+index+1; i++){
		mat[i] = malloc((ncols+index)*sizeof(int*));
		if (!mat[i]){
			printf("Matrix MAT could not be allocted\n The exec. will Exit now\n");
			exit(1);
		}
	}
	
return mat;
}

Originally Posted by cfdprogrammer

Hi again,

... instead of a BUS error, I now get a segmentation fault

Apologies, I solved the segmentation fault. I was freeing the memory twice!
So, to sum it up: I get a bus error with the original version of the function, but it works fine when I use a pointer to function instead.
What would be the cause to it? Are they not equivalent?

thanks

Originally Posted by matsp

Ah, yes, to modify a pointer to pointer, you need a pointer to pointer to pointer (so int ***mat, and use *mat inside the function - it may be better to use a new variable inside the function, and before the function returns, you set the *mat = tmpMat or whatever you call it).

--
Mats

Great, thank you very much.
I'll use the pointer to function now since it works well as it is.

Regards,
cfd

I now get a new error in execution:

this line repeated many many times

Code:

meteoIni.a(32753) malloc: *** error for object 0x30303130: 
Non-aligned pointer being freed (2)

does anyone know what is happening?
thanks

Originally Posted by matsp

Probably that you are freeing something that you didn't allocate.

--
Mats

Hi,

that is the strange thing, since I am only freeing what I am allocating.
I am allocating 6 different variables with this new function, and what is strange about the error that I get, is that it is only happening when I allocate ONE of the six variables, and this variable is not even the last to be allocated and freed

thank you again

Thank you, I'll figure it out although I can't explain it. It worked with no problem when I was allocating it with the NR library with the same range
strange

best