问题描述
我一直在使用 Valgrind 查找代码中的内存泄漏，虽然未发现任何内存泄漏，但报告了一些错误，所有错误均源于单个函数/类方法:
I've been using Valgrind to look for memory leaks in my code, and while no memory leaks are being found, some errors are reported all of them originating at a single function/class method:
==17043== ERROR SUMMARY: 10100 errors from 3 contexts (suppressed: 0 from 0)
==17043==
==17043== 100 errors in context 1 of 3:
==17043== Syscall param socketcall.sendto(msg) points to uninitialised byte(s)
==17043== at 0x5441DA2: send (send.c:28)
==17043== by 0x404C2D: unix_socket::sendMsg(char, double) (in /home/joao/CloudPT/Bolsa/Webots/controllers/darwin-pi2/client)
==17043== by 0x404F1C: unix_socket::sendVectorXd(Eigen::Matrix<double, -1, 1, 0, -1, 1> const&) (in /home/joao/CloudPT/Bolsa/Webots/controllers/darwin-pi2/client)
==17043== by 0x401F2A: main (in /home/joao/CloudPT/Bolsa/Webots/controllers/darwin-pi2/client)
==17043== Address 0x7feffff61 is on thread 1's stack
==17043== Uninitialised value was created by a stack allocation
==17043== at 0x404BE6: unix_socket::sendMsg(char, double) (in /home/joao/CloudPT/Bolsa/Webots/controllers/darwin-pi2/client)
==17043==
==17043==
==17043== 100 errors in context 2 of 3:
==17043== Syscall param socketcall.sendto(msg) points to uninitialised byte(s)
==17043== at 0x5441DA2: send (send.c:28)
==17043== by 0x404C2D: unix_socket::sendMsg(char, double) (in /home/joao/CloudPT/Bolsa/Webots/controllers/darwin-pi2/client)
==17043== by 0x404E8A: unix_socket::sendVectorXd(Eigen::Matrix<double, -1, 1, 0, -1, 1> const&) (in /home/joao/CloudPT/Bolsa/Webots/controllers/darwin-pi2/client)
==17043== by 0x401F2A: main (in /home/joao/CloudPT/Bolsa/Webots/controllers/darwin-pi2/client)
==17043== Address 0x7feffff61 is on thread 1's stack
==17043== Uninitialised value was created by a stack allocation
==17043== at 0x404BE6: unix_socket::sendMsg(char, double) (in /home/joao/CloudPT/Bolsa/Webots/controllers/darwin-pi2/client)
==17043==
==17043==
==17043== 9900 errors in context 3 of 3:
==17043== Syscall param socketcall.sendto(msg) points to uninitialised byte(s)
==17043== at 0x5441DA2: send (send.c:28)
==17043== by 0x404C2D: unix_socket::sendMsg(char, double) (in /home/joao/CloudPT/Bolsa/Webots/controllers/darwin-pi2/client)
==17043== by 0x404EE8: unix_socket::sendVectorXd(Eigen::Matrix<double, -1, 1, 0, -1, 1> const&) (in /home/joao/CloudPT/Bolsa/Webots/controllers/darwin-pi2/client)
==17043== by 0x401F2A: main (in /home/joao/CloudPT/Bolsa/Webots/controllers/darwin-pi2/client)
==17043== Address 0x7feffff61 is on thread 1's stack
==17043== Uninitialised value was created by a stack allocation
==17043== at 0x404BE6: unix_socket::sendMsg(char, double) (in /home/joao/CloudPT/Bolsa/Webots/controllers/darwin-pi2/client)
==17043==
==17043== ERROR SUMMARY: 10100 errors from 3 contexts (suppressed: 0 from 0)
错误所指向的sendMsg(const char _type, const double _value)是unix_socket类的一部分:
The sendMsg(const char _type, const double _value), that the errors are pointing at, is part of unix_socket class:
//...
typedef struct{
char type;
double value;
} MESSAGE;
//...
int unix_socket::sendMsg(const char _type, const double _value){
MESSAGE msg;
msg.type=_type;
msg.value=_value;
int n = send(client_sock, &msg, sizeof(msg), 0);
if (n < 0) {
perror("send");
return -1;
}
c_sent=msg.type;
v_sent=msg.value;
return 0;
}
我看不出问题所在.未初始化的值到底在哪里?还是我应该忽略Valgrind报告的错误?
I don't see what is the problem. Where exactly are the uninitialized values? Or should I just ignore the errors reported by Valgrind?
推荐答案
查看MESSAGE结构:
typedef struct{
char type;
double value;
} MESSAGE;
由于数据结构的对齐方式，value的地址可能被迫对齐到字长倍数的地址.因此，在MESSAGE::type和MESSAGE::value之间填充了几个未使用的字节.这些是Valgrind未初始化并因此报告的字节.
Due to data structure alignment, value's address may be forced to align to address of a multiple of word size. Therefore, several unused bytes is padded between MESSAGE::type and MESSAGE::value. Those are the bytes which weren't initialized and thus reported by Valgrind.
作为一种解决方法，您可以通过memset()强制初始化整个结构.
As a workaround, you could force initializing the whole struct by memset().
MESSAGE msg;
memset(&msg, 0, sizeof(MESSAGE));
msg.type=_type;
msg.value=_value;
这篇关于“指向未初始化的字节". Valgrind错误的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！