c - 如何发现代码中的内存泄漏问题

Question

我有内存泄漏问题，我怀疑问题可能出在下面的“base64_decode()”函数中。另外，请阅读代码中的注释。

uint8_t *unbase64_ct = NULL;
uint8_t *unbase64_sig = NULL;

int i = 0;

 // ptr is just a buffer of fixed size containing encoded data 
 //separated with delim (i.e. "&" sign). The ptr may contain 
 //base64(ct)&base64(sig)& where base64(ct) is encoded ciphertext and 
 //base64(sig) is encoded signature of public key cryptography

char *next = NULL;
char *tokens = strtok_r(ptr, delim, &next);

do
{
    if(i == 0)
    {
        int ln = strlen(tokens);
        unbase64_ct = base64_decode((uint8_t*)tokens, (uint32_t*)&ln);
        i++;
        continue;
    }

    if(i == 1)
    {
        int ln = strlen(tokens);
        unbase64_sig = base64_decode((uint8_t*)tokens, (uint32_t*)&ln);
        i++;
        continue;
    }
}
while((tokens = strtok_r(NULL, delim, &next)) != NULL);

// I believe this function leaves leftovers.
uint8_t *base64_decode(uint8_t *bbuf, uint32_t *len)
{
     uint8_t *ret;
     uint32_t bin_len;

     bin_len = (((strlen((char*)bbuf) + 3)/4) * 3);
     ret = (uint8_t*)malloc(bin_len);

    *len = EVP_DecodeBlock(ret, bbuf, strlen((char*)bbuf));
     // Following good code practice, ret must be freed within the 
     //code block... 
     //However, how do i pass random number of bytes in the 
     //different way without using malloc?
     return ret;
}

// I release here unbase64_ct and unbase64_sig as the output is 
// dynamically allocated.

free(tokens);
free(unbase64_ct);
free(unbase64_sig);

它工作得很好，但是在多次运行整个代码(例如 1000 次)后，它会停止在 100 - 1000 范围内的随机值上。如何在没有动态内存分配的情况下重写 base64_decode 函数，或者发现内存泄漏问题我看不到？

Answer 1

每次调用base64_decode都会分配一个新的缓冲区，因此unbase64_ct和unbase64_sig会被多次分配，但只释放一次。