c - 如何在 GCC 4.6.3 中更改堆和堆栈内存大小？

Question

在使用 malloc 时，我注意到分配的指针为空。我想在代码执行期间为堆内存分配更多大约 30 MB 的内存。如何在 Ubuntu 12.04 LTS 上使用 GCC 4.6.3 作为编译器？我应该分配更多的堆栈内存吗？会更好吗？

谢谢

编辑代码有问题的部分，代码在if语句后终止。

#include <stdio.h>
#include <math.h>
#include <limits.h>
#include <stdlib.h>
#define a0 0.53 
#define N LONG_MAX
// This value of N is the highest possible number in long double
// data format over 100. Higher is not possible due to the size of 
// the default heap memory. Change its value  to adjust the precision of 
// integration and computation time. Since exponential decays really fast
// a modest value of N is enough for this integration.
// The discrete integral may be defined as follows:
long double trapezoid(long double x[],long double f[]) {
  int i;
  long double dx = x[1]-x[0];
  long double sum = 0.5*(f[0]+f[N]);

    for (i = 1; i <  N; i++) 
        sum+=f[i];
  return sum*dx;  
}
main() {
    printf("LONG_MAX constant has the following value: %ld \n", LONG_MAX);
    long double * P = malloc(N * sizeof(long double));
    long double * r = malloc(N * sizeof(long double));
    long double * PP = malloc(N * sizeof(long double));
    // The if statement is to check if the memory allocation has 
    // been done and terminate the program otherwise.
    if (P == 0 || r == 0)
        {
            printf("ERROR: Out of memory\n");
            return 1;
        }
    // Declare and initialize the loop variable
}