Question

所以基本上我的输入是一个未知大小的字符串。我所做的就是创建一个函数来扫描它并为每个char动态分配内存。

char* GetUnknownStr(){
char* string = NULL;
char input = 0;
int charCount = 0;
//scan for chars until ENTER is pressed
while (input != '\n'){
    scanf("%c", &input);
    //on last iteration (when ENTER is pressed) break from loop
    if (input == '\n')
        break;
    //realloc new amount of chars
    string = (char*)realloc(string, (++charCount)*sizeof(char));
    //check if realloc didnt fail
    if (string == NULL){
        puts("failed to allocate");
        return 0;
    }
    //assign char scanned into string
    string[charCount-1] = input;
}
//realloc 1 more char for '\0' in the end of string
string = (char*)realloc(string, (++charCount)*sizeof(char)); <--leak
string[charCount-1] = '\0';
return string;
}

Valgrind的：

==30911== HEAP SUMMARY:
==30911==     in use at exit: 4 bytes in 1 blocks
==30911==   total heap usage: 7 allocs, 6 frees, 16 bytes allocated
==30911== 
==30911== 4 bytes in 1 blocks are definitely lost in loss record 1 of 1
==30911==    at 0x4A05255: realloc (vg_replace_malloc.c:476)
==30911==    by 0x40091F: GetUnknownStr (in /u/stud/krukfel/C/e5/a.out)
==30911==    by 0x40266B: main (in /u/stud/krukfel/C/e5/a.out)
==30911== 
==30911== LEAK SUMMARY:
==30911==    definitely lost: 4 bytes in 1 blocks
==30911==    indirectly lost: 0 bytes in 0 blocks
==30911==      possibly lost: 0 bytes in 0 blocks
==30911==    still reachable: 0 bytes in 0 blocks
==30911==         suppressed: 0 bytes in 0 blocks
==30911== 
==30911== For counts of detected and suppressed errors, rerun with: -v
==30911== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 6 from 6)

由于某种原因，我得到了内存泄漏，无法弄清楚为什么，尝试使用valgrind，但从它没有多大意义。谢谢！

Answer 1

除了轻微的风格问题，例如投射malloc并乘以sizeof(char)，您的代码就可以了。实际泄漏位于调用函数的代码中。

处理内存泄漏的一个核心问题是所有权问题。一旦你知道谁拥有分配的内存块，就知道需要释放它以避免泄漏。在这种情况下，字符串在GetUnknownStr内创建，但随后该字符串的所有权将传输给调用者。您的GetUnknownStr函数的调用者负责调用函数返回的结果free。如果调用者没有释放字符串，则会报告泄漏。泄漏的位置将是最后重新分配的点，即您在代码中标记的行。

内存泄漏与动态字符串

1 个答案: