您在问题中提供的输出包含以下行：
==5190== Use --track-origins=yes to see where uninitialised values come from
根据此消息，您应该运行./ex4像这样：
valgrind --track-origins=yes ./ex4
为了避免Valgrind无法找到调试信息的一些问题，可以使用静态链接：
gcc -static -g -o ex4 ex4.c
Valgrind 的输出将包含如下消息Uninitialised value was created by a stack allocation:
==17673== Memcheck, a memory error detector
==17673== Copyright (C) 2002-2011, and GNU GPL'd, by Julian Seward et al.
==17673== Using Valgrind-3.7.0 and LibVEX; rerun with -h for copyright info
==17673== Command: ./ex4
...
==17673== Use of uninitialised value of size 4
==17673== at 0x805CA7B: _itoa_word (in /home/user/ex4)
==17673== by 0x8049D5F: printf (in /home/user/ex4)
==17673== by 0x8048ECD: main (ex4.c:8)
==17673== Uninitialised value was created by a stack allocation
==17673== at 0x8048EFA: bad_function (ex4.c:17)
...
==17673== Use of uninitialised value of size 4
==17673== at 0x805CA7B: _itoa_word (in /home/user/ex4)
==17673== by 0x8049D5F: printf (in /home/user/ex4)
==17673== by 0x80490BE: (below main) (in /home/user/ex4)
==17673== Uninitialised value was created by a stack allocation
==17673== at 0x8048EBE: main (ex4.c:4)
...
I am -1094375076 years old.
...
I am -1094369310 inches tall.
...
==17673==
==17673== HEAP SUMMARY:
==17673== in use at exit: 0 bytes in 0 blocks
==17673== total heap usage: 0 allocs, 0 frees, 0 bytes allocated
==17673==
==17673== All heap blocks were freed -- no leaks are possible
==17673==
==17673== For counts of detected and suppressed errors, rerun with: -v
==17673== ERROR SUMMARY: 83 errors from 21 contexts (suppressed: 0 from 0)
File ex4.c:
1 #include <stdio.h>
2
3 int main()
4 {
5 int age = 10;
6 int height;
7
8 bad_function();
9
10 printf("I am %d years old.\n");
11 printf("I am %d inches tall.\n", height);
12
13 return 0;
14 }
15
16 int bad_function()
17 {
18 int x;
19 printf("%d\n", x);
20 }
Valgrind 的输出并不理想。它标识包含未初始化变量的堆栈帧（函数），但不打印变量的名称。
在 VirtualBox 下运行 Linux 对 Valgrind 没有影响。
