C語言隨筆

@一般而言，區域變數會被存放在stack上，而stack在很多機器上都無法很大，這個時候的變通辦法就是將大容量的變數宣告成static的儲存類別，若是遞迴程式，則可能需要重新安排程式的架構了。

@Below is an example code from stack over flow, the subject is

returning a local variable from function in C and return

here we get the warning as below:

"warning: function returns address of local variable"

#include <stdio.h>

int foo1(void)
{
    int p;
    p = 99;
    return p;
}

char *foo2(void)
{
    char buffer[] = "test_123";
    return buffer;
}

int *foo3(void)
{
    int t[3] = {1,2,3};
    return t;
}

int main(void)
{
    int *p;
    char *s;

    printf("foo1: %d\n", foo1());
    printf("foo2: %s\n", foo2());
    printf("foo3: %d, %d, %d\n", p[0], p[1], p[2]);
    return 0;
}

And there's one guy has answer as below:

For foo1(), you return a copy of the local variable, not the local variable itself.

For the other functions, you return a copy of a pointer to a local variable. However, that local variable is deallocated when the function finishes, so you end up with nasty issues if you try to reference it afterwards.