C：从函数返回char *会使printf崩溃

Question

因此，这是包含printf的代码（带有行号，这来自think.c）：

30: char *think = getRandomMemory();
31: printf("\33[2K\r");
32: if(think == NULL)
33:     think = "NULL";
34: printf("I have an idea: %s\n", think);
35: parse(think);
36: freeMemory(think);
37: printf("> ");

而getRandomMemory()的代码可确保返回的指针指向堆分配的空间：

char *getRandomMemory()
{
    char *ret;

    // --SNIP--

    size_t l = strlen(ret) + 1;
    char *rret = getMemory(sizeof(char) * l);
    for(int i = 0; i < l; i++)
        rret[i] = ret[i];
    printf("--- %s ---\n", rret);
    return rret;
}

最后，这是gdb在运行此命令时给我的。 请注意，“ ---测试---”来自上面的“ printf("--- %s ---\\n", rret) ”：

(gdb) run
Starting program: /home/v10lator/Private/projekte/KI/Lizzy 
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib64/libthread_db.so.1".
Loading Lizzy 0.1... Done!

> --- test ---
[New Thread 0x7ffff781f700 (LWP 32359)]

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7ffff781f700 (LWP 32359)]
0x00007ffff7869490 in _IO_vfprintf_internal (s=<optimized out>, format=<optimized out>, 
ap=ap@entry=0x7ffff781ee68) at vfprintf.c:1642
1642    vfprintf.c: Datei oder Verzeichnis nicht gefunden.
(gdb) bt
#0  0x00007ffff7869490 in _IO_vfprintf_internal (s=<optimized out>, format=<optimized out>, 
ap=ap@entry=0x7ffff781ee68) at vfprintf.c:1642
#1  0x00007ffff7919235 in ___printf_chk (flag=1, format=<optimized out>) at printf_chk.c:35
#2  0x00000000004016bc in printf () at /usr/include/bits/stdio2.h:104
#3  run (first=<optimized out>) at think.c:34
#4  0x00007ffff7bc64c6 in start_thread (arg=0x7ffff781f700) at pthread_create.c:333
#5  0x00007ffff790a86d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109

我真的不知道这是怎么回事，所以希望有人能看到错误。

//编辑：忘记了getMemory / freeMemory函数：

/*
  * This allocates memory.
  * The difference between usig malloc directly is that this function will
  * print an error and exit the program in case something bad happens.
  */
char *getMemory(size_t size)
{
    char *mem = malloc(size);
    if(mem == NULL)
        crashWithMsg("Internal error (malloc failed)!");
    return mem;
}

/*
 * This deallocates memory.
 * The difference between using free directly is that this function will
 * set the pointer to NULL afterwards.
 */
void freeMemory(void **ptr)
{
    free(*ptr);
    *ptr = NULL;
}

Answer 1

问题是您对freeMemory的调用：

freeMemory(think);

您已经对该函数进行了编码，以获取指向要释放的内存的指针的地址，而不是指向指针本身的地址。 因此，您需要使用以下命令调用它：

freeMemory(&think);

Answer 2

[删除了错误的断言]

为什么不使用strcpy()呢？