🔄 Returning a Pointer to a Local Variable : C/C++ 🆚 Java ☕

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⚠️ ️One of the classic pitfalls in C/C++ programming is returning a pointer to a local variable.

At first glance, it may seem trivial to store a computed value in a local array and then return a pointer to it. But as soon as that function ends, the local variable goes out of scope 🚫. This can lead to undefined behavior, ranging from printing garbage characters to crashing 💥 your program altogether.

In this post, we’ll walk through:

1. A buggy version of a C++ program returning a pointer to a local array.
2. A corrected C++ version that avoids undefined behavior by dynamically allocating memory on the heap.
3. An equivalent Java code snippet, showing how memory management in Java sidesteps this particular issue.

Finally, we’ll look at the expected outputs of these snippets and discuss why they differ.

🚨 The Buggy C++ Code

#include <stdio.h>
#include <string.h>
#include <time.h>

char* get_date()
{
    char buf[80];
    time_t now = time(0);
    strcpy(buf, ctime(&now));
    return buf;  // Returning pointer to a local stack array
}

int main(int argc, char *argv[])
{
    char *date = get_date();
    printf("date=%s\n", date);
    return 0;
}