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#include <bits/stdc++.h>
int main(){
    int a, b = 10, r;
    printf("%d\n", a);
}

==13235== Memcheck, a memory error detector
==13235== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==13235== Using Valgrind-3.15.0 and LibVEX; rerun with -h for copyright info
==13235== Command: ./assign
==13235==
==13235== error calling PR_SET_PTRACER, vgdb might block
==13235== Conditional jump or move depends on uninitialised value(s)
==13235==    at 0x4AAEAD8: __vfprintf_internal (vfprintf-internal.c:1687)
==13235==    by 0x4A98EBE: printf (printf.c:33)
==13235==    by 0x1091B1: main (assignment.cpp:5)
==13235==
==13235== Use of uninitialised value of size 8
==13235==    at 0x4A9281B: _itoa_word (_itoa.c:179)
==13235==    by 0x4AAE6F4: __vfprintf_internal (vfprintf-internal.c:1687)
==13235==    by 0x4A98EBE: printf (printf.c:33)
==13235==    by 0x1091B1: main (assignment.cpp:5)
==13235==
==13235== Conditional jump or move depends on uninitialised value(s)
==13235==    at 0x4A9282D: _itoa_word (_itoa.c:179)
==13235==    by 0x4AAE6F4: __vfprintf_internal (vfprintf-internal.c:1687)
==13235==    by 0x4A98EBE: printf (printf.c:33)
==13235==    by 0x1091B1: main (assignment.cpp:5)
==13235==
==13235== Conditional jump or move depends on uninitialised value(s)
==13235==    at 0x4AAF3A8: __vfprintf_internal (vfprintf-internal.c:1687)
==13235==    by 0x4A98EBE: printf (printf.c:33)
==13235==    by 0x1091B1: main (assignment.cpp:5)
==13235==
==13235== Conditional jump or move depends on uninitialised value(s)
==13235==    at 0x4AAE86E: __vfprintf_internal (vfprintf-internal.c:1687)
==13235==    by 0x4A98EBE: printf (printf.c:33)
==13235==    by 0x1091B1: main (assignment.cpp:5)
==13235== 0
==13235==
==13235== HEAP SUMMARY:
==13235==     in use at exit: 0 bytes in 0 blocks
==13235==   total heap usage: 2 allocs, 2 frees, 73,216 bytes allocated
==13235==
==13235== All heap blocks were freed -- no leaks are possible
==13235==
==13235== Use --track-origins=yes to see where uninitialised values come from
==13235== For lists of detected and suppressed errors, rerun with: -s
==13235== ERROR SUMMARY: 5 errors from 5 contexts (suppressed: 0 from 0)

我无法从此输入中出错，堆摘要显示什么，为什么未初始化的变量为size = 8？另外，“总堆使用量：2个分配，2个空闲，分配的73,216个字节”是什么意思？“错误摘要：来自5个上下文的5个错误（被抑制：从0开始为0）”？

o梦倾城

2020-05-23 23:32:11

未初始化的变量错误来自此行：

printf("%d\n", a);

since you are using a without giving it an initial value. This invokes undefined behavior, and should never be done.

The size of the variable being 8 bytes suggests that you are compiling on a 64bit architecture, where an int is 8 bytes, or 64 bits.

总堆使用情况只是程序执行期间已分配并释放的所有内存的摘要。由于最后使用的字节数为0，这意味着您的程序不会泄漏任何内存。

zamet

valgrind发出的第一条消息指出“条件跳转或移动取决于未初始化的值”，并在代码中引用此行：

This line uses the variable a. If you then look at the preceding line:

int a, b = 10, r;

You'll see that a is never assigned a value. That is, it is uninitialized. This is what valgrind is complaining about. You can fix this by giving a a value:

int a = 1, b = 10, r;

其余的valgrind消息引用了文件中的同一行代码，因此其余的错误从第一个开始出现，并且修复一个错误应该可以修复其余的错误。

我该如何解释此错误，堆摘要，未初始化的变量？