matrix.h
#if !defined MATRIX_H
#define MATRIX_H
#define _CRT_SECURE_NO_WARNINGS
#include <stdlib.h>
#include <stdio.h>

struct matrix
{
	size_t rows, cols;
	double*data;
};
extern struct matrix** leggi_matrici(const char*filename, size_t*size);
#endif

matrix.c
#include "matrix.h"
struct matrix** leggi_matrici(const char*filename, size_t *size)
{
	*size = 0;
	FILE* f = fopen(filename, "rt");
	if (f==NULL)
	{
		return NULL;
	}
	struct matrix** ret = NULL;
	struct matrix*tmp=malloc(sizeof(struct matrix));
	tmp->data = NULL;
	int err=0;
	int test = fscanf(f, "%u\n",size);
	if (test != 1)
		return ret;
	ret = realloc(ret,(*size) * sizeof(struct matrix*));
	unsigned count = 0;
	while (count<*size)
	{
		test = fscanf(f, "%u,%u,", &(tmp->rows),&(tmp->cols));
		if (test != 2)
			err = 1;
		tmp->data = realloc(tmp->data, (tmp->rows*tmp->cols) * sizeof(double));
		for (size_t i = 0; i < (tmp->rows*tmp->cols); i++)
		{
			test = fscanf(f, "%lf,", tmp->data + i);
			if (test != 1)
			{
				err = 1;
				break;
			}
		}
		if (err)
		{
			for (size_t i = 0; i < count; i++)
			{
				free(ret[count]);
				free(tmp->data);
				free(tmp);
				free(ret);
				return NULL;
			}
			break;
		}
		else
		{
			ret[count]=malloc(sizeof(struct matrix));
			*(ret[count]) = *tmp;
			ret[count]->data = realloc(ret[count]->data, (tmp->rows*tmp->cols) * sizeof(double));
			for (size_t i = 0; i < tmp->rows*tmp->cols; i++)
			{
				ret[count]->data[i] = tmp->data[i];
			}
			count++;
		}
	}

	return ret;
}