[英]Memory leak after using calloc and free?
I tested my software with "valgrind --leak-check=full", and it shows: 我用“ valgrind --leak-check = full”测试了我的软件,它显示:
==90862== 7,627 bytes in 4 blocks are definitely lost in loss record 858 of 897
==90862== at 0x4C2FB55: calloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==90862== by 0xD64991C: concat(int, ...) (Client.cpp:150)
I can't understand why, because I use free() after calloc. 我不明白为什么,因为我在calloc之后使用free()。 Here's my code:
这是我的代码:
char* p = concat(2, buffOld, buff);
char *x;
while(true) {
x = p;
p = strstr(p,"\\final\\");
if(p == NULL) { break; }
*p = 0;
p+=7;
parseIncoming((char *)x,strlen(x));
}
free(p);
And the "concat" function: 和“ concat”功能:
char* concat(int count, ...)
{
va_list ap;
int i;
// Find required length to store merged string
int len = 1; // room for NULL
va_start(ap, count);
for(i=0 ; i<count ; i++)
len += strlen(va_arg(ap, char*));
va_end(ap);
// Allocate memory to concat strings
char *merged = (char*)calloc(sizeof(char),len);
int null_pos = 0;
// Actually concatenate strings
va_start(ap, count);
for(i=0 ; i<count ; i++)
{
char *s = va_arg(ap, char*);
strcpy(merged+null_pos, s);
null_pos += strlen(s);
}
va_end(ap);
return merged;
}
What I do wrong? 我做错了什么?
I can't understand why, because I use free() after calloc
我不明白为什么,因为我在calloc之后使用free()
Yes, but (if I understand correctly) you free()
the wrong pointer. 是的,但是(如果我理解正确),您
free()
了错误的指针。
You should copy p
in another pointer (before modifing it) and free()
the save copy. 您应该将
p
复制到另一个指针中(在对其进行修改之前),并使用free()
保存副本。
Look at your code 看你的代码
char* p = concat(2, buffOld, buff);
char *x;
while(true) {
x = p;
p = strstr(p,"\\final\\");
if(p == NULL) { break; }
*p = 0;
p+=7;
parseIncoming((char *)x,strlen(x));
}
free(p);
The pointer p
is initialized with the calloc-ed pointer but the while
cicle modify it and return only when p
is NULL
. 指针
p
已使用calloc-ed指针初始化, while
cicle对其进行了修改,并且仅在p
为NULL
时返回。
So, when you call 所以,当你打电话
free(p)
you're calling 你在打电话
free(nullptr)
--- EDIT --- -编辑-
I still don't understand it.
我还是不明白。 I added free(x) at the end, and it crashes
我在最后添加了free(x),它崩溃了
My initial suggestion to free(x)
was a mistake of mine because I didn't pointed the attention to the fact that x
is initializes with the p
value but is modified in the while
loop. 我最初对
free(x)
建议是我的一个错误,因为我没有将注意力集中在x
用p
值初始化但在while
循环中修改的事实。 Thanks again to Johnny Mopp for pointing my attention to it. 再次感谢约翰尼·莫普(Johnny Mopp)引起我的注意。
I suggest the use of another variable to memorize the original value of p
(the exact value returned by calloc()
) and free this value. 我建议使用另一个变量来记住
p
的原始值(由calloc()
返回的确切值)并释放该值。
Something like 就像是
char* p = concat(2, buffOld, buff);
char *x;
char * const forFree = p; /* <--- saving calloc() returned value */
while(true) {
x = p;
p = strstr(p,"\\final\\");
if(p == NULL) { break; }
*p = 0;
p+=7;
parseIncoming((char *)x,strlen(x));
}
free(forFree);
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