Valgrind的抱怨，当函数返回字符数组的指针

Question

我想这是一个新手ç的问题，但我无法找到答案。这是我的代码：

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

char *copy(char *in) { 
    char *out = (char *) malloc(strlen(in)+1); 
    strcpy(out,in); 
    return out; 
} 

int main() {  
    char *orig = (char *) malloc(100); 
    strcpy(orig,"TEST"); 
    printf("Original reads : %s\n",orig); 
    printf("Copy reads  : %s\n",copy(orig)); 
} 

它工作正常，但是的valgrind --leak检查= YES抱怨：

==4701== Memcheck, a memory error detector 
==4701== Copyright (C) 2002-2013, and GNU GPL'd, by Julian Seward et al. 
==4701== Using Valgrind-3.10.0 and LibVEX; rerun with -h for copyright info 
==4701== Command: ./copy 
==4701== 
Original reads : TEST 
Copy reads  : TEST 
==4701== 
==4701== HEAP SUMMARY: 
==4701==  in use at exit: 105 bytes in 2 blocks 
==4701== total heap usage: 2 allocs, 0 frees, 105 bytes allocated 
==4701== 
==4701== 5 bytes in 1 blocks are definitely lost in loss record 1 of 2 
==4701== at 0x4C28C20: malloc (vg_replace_malloc.c:296) 
==4701== by 0x400609: copy (in /root/alfred/copy) 
==4701== by 0x40066C: main (in /root/alfred/copy) 
==4701== 
==4701== 100 bytes in 1 blocks are definitely lost in loss record 2 of 2 
==4701== at 0x4C28C20: malloc (vg_replace_malloc.c:296) 
==4701== by 0x400638: main (in /root/alfred/copy) 
==4701== 
==4701== LEAK SUMMARY: 
==4701== definitely lost: 105 bytes in 2 blocks 
==4701== indirectly lost: 0 bytes in 0 blocks 
==4701==  possibly lost: 0 bytes in 0 blocks 
==4701== still reachable: 0 bytes in 0 blocks 
==4701==   suppressed: 0 bytes in 0 blocks 
==4701== 
==4701== For counts of detected and suppressed errors, rerun with: -v 
==4701== ERROR SUMMARY: 2 errors from 2 contexts (suppressed: 0 from 0) 

可能有人请告诉我，我究竟做错了什么？提前致谢！

Answer 1

您正在分配copy函数中的内存块，但从不释放它。所以你的代码会产生一个内存泄漏，这是Valgrind报告的。你的代码的正确版本应该是

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

char *copy(char *in) { 
    char *out = malloc(strlen(in)+1); 
    //You need to check malloc result here! 
    strcpy(out,in); 
    return out; 
} 

int main() {  
    char *orig = (char *) malloc(100); 
    strcpy(orig,"TEST"); 
    printf("Original reads : %s\n",orig); 
    char* copy = copy(orig); 
    printf("Copy reads  : %s\n",copy); 
    free(orig); 
    free(copy); 
    return 0; 
} 

而且do not cast malloc() results.

Answer 2

您是的malloc（）'荷兰国际集团两次，但不免费（）他们。因此，valgrind抱怨泄漏。 释放你分配的内存块，它应该没问题。

char *p = copy(orig); 
    printf("Copy reads  : %s\n", p); 
    free(orig); 
    free(p);