Valgrind Memcheck输出

Question

我正在使用valgrind在我的系统上找到内存泄漏,我收到了这个输出

==9697== Memcheck, a memory error detector
==9697== Copyright (C) 2002-2011, and GNU GPL'd, by Julian Seward et al.
==9697== Using Valgrind-3.7.0 and LibVEX; rerun with -h for copyright info
==9697== Command: bin/vfirewall-monitor
==9697== 
==9697== 
==9697== HEAP SUMMARY:
==9697==     in use at exit: 0 bytes in 0 blocks
==9697==   total heap usage: 1 allocs, 1 frees, 37 bytes allocated
==9697== 
==9697== All heap blocks were freed -- no leaks are possible
==9697== 
==9697== For counts of detected and suppressed errors, rerun with: -v
==9697== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 2 from 2)
==9700== Thread 2:
==9700== Conditional jump or move depends on uninitialised value(s)
==9700==    at 0x56DE3B1: vfprintf (vfprintf.c:1630)
==9700==    by 0x5706441: vsnprintf (vsnprintf.c:120)
==9700==    by 0x56E6971: snprintf (snprintf.c:35)
==9700==    by 0x403A1A: save_interfaces_info (interfaces.c:351)
==9700==    by 0x403DC4: get_all_system_info (kernel.c:135)
==9700==    by 0x547DE99: start_thread (pthread_create.c:308)
==9700==    by 0x57873FC: clone (clone.S:112)
==9700==  Uninitialised value was created by a heap allocation
==9700==    at 0x4C2B6CD: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==9700==    by 0x403D6F: get_all_system_info (kernel.c:118)
==9700==    by 0x547DE99: start_thread (pthread_create.c:308)
==9700==    by 0x57873FC: clone (clone.S:112)
==9700== 

它说没有错误,但我在kernel.c上有一个未初始化的值:118.

这是我在118的1kernel.c1:

117    Interface * ifaces;
118    ifaces = malloc(sizeof (Interface));
119    ifaces->next_interface = NULL;

我不明白这里有什么问题.我在找错了地方吗？或者我正在阅读valgrind日志错误？

Answer 1

错误是interfaces.c:351,它正在调用snprintf未初始化的值.

该值是在kernel.c:118使用时分配的malloc.您可能知道,malloc不会初始化它返回的内存,它可能包含垃圾.这就是它的抱怨.

很可能你的Interface对象有一个char name[]或一些像第一个成员,你传递该成员snprintf没有设置它.

编辑:我知道问题的原因是第一个成员Interface是因为如果它是一些其他内存valgrind会说类似Uninitialised value is 4 bytes into a block created by a heap allocation而不是只是Uninitialised value was created by a heap allocation.