我试图弄清楚 Valgrind 的用法，所以我做了一个简单的程序，但是当我在课堂上进行动态内存分配时，Valgrind 似乎给出了一个奇怪的错误。
我的程序是：
class Valgrind_testclass
{
Valgrind_testclass *Obj;
public:
Valgrind_testclass() {
// Obj = new Valgrind_testclass(); // Test point #3
}
~Valgrind_testclass() {
//delete Obj; // Test point #4
}
};
int main()
{
Valgrind_testclass valObj;
// Valgrind_testclass * valObjPtr = new Valgrind_testclass(); // Test point #1
//delete valObjPtr; // Test point #2
return 0;
}
带有注释掉的测试点 Valgrind 给了我以下信息：
==5273== HEAP SUMMARY:
==5273== in use at exit: 0 bytes in 0 blocks
==5273== total heap usage: 0 allocs, 0 frees, 0 bytes allocated
我想这是预期的结果。
现在，当我取消注释测试点 #1 时：
==5288== HEAP SUMMARY:
==5288== in use at exit: 4 bytes in 1 blocks
==5288== total heap usage: 1 allocs, 0 frees, 4 bytes allocated
==5288==
==5288== Searching for pointers to 1 not-freed blocks
==5288== Checked 102,116 bytes
==5288==
==5288== 4 bytes in 1 blocks are definitely lost in loss record 1 of 1
这又是正确的结果，因为我没有执行删除。
在未注释测试点 #2 的情况下，我得到：
==5300== HEAP SUMMARY:
==5300== in use at exit: 0 bytes in 0 blocks
==5300== total heap usage: 1 allocs, 1 frees, 4 bytes allocated
==5300==
==5300== All heap blocks were freed -- no leaks are possible
再次正确的结果。
现在我取消注释测试点#3，我希望 Valgrind 能够检测到内存泄漏。这就是我得到的：
==5313== Process terminating with default action of signal 11 (SIGSEGV)
==5313== Access not within mapped region at address 0xBE17AFE4
==5313== at 0x40263A0: operator new(unsigned int) (vg_replace_malloc.c:255)
==5313== If you believe this happened as a result of a stack
==5313== overflow in your program's main thread (unlikely but
==5313== possible), you can try to increase the size of the
==5313== main thread stack using the --main-stacksize= flag.
==5313== The main thread stack size used in this run was 8388608.
==5313== Stack overflow in thread 1: can't grow stack to 0xbe17afe0
==5313==
==5313== Process terminating with default action of signal 11 (SIGSEGV)
==5313== Access not within mapped region at address 0xBE17AFE0
==5313== at 0x402040C: _vgnU_freeres (vg_preloaded.c:58)
==5313== If you believe this happened as a result of a stack
==5313== overflow in your program's main thread (unlikely but
==5313== possible), you can try to increase the size of the
==5313== main thread stack using the --main-stacksize= flag.
==5313== The main thread stack size used in this run was 8388608.
==5313==
==5313== HEAP SUMMARY:
==5313== in use at exit: 1,047,576 bytes in 261,894 blocks
==5313== total heap usage: 261,894 allocs, 0 frees, 1,047,576 bytes allocated
==5313==
==5313== Searching for pointers to 261,894 not-freed blocks
==5313== Checked 5,339,952 bytes
==5313==
==5313== LEAK SUMMARY:
==5313== definitely lost: 0 bytes in 0 blocks
==5313== indirectly lost: 0 bytes in 0 blocks
==5313== possibly lost: 0 bytes in 0 blocks
==5313== still reachable: 1,047,576 bytes in 261,894 blocks
==5313== suppressed: 0 bytes in 0 blocks
==5313== Reachable blocks (those to which a pointer was found) are not shown.
==5313== To see them, rerun with: --leak-check=full --show-reachable=yes
==5313==
==5313== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 17 from 6)
我不确定为什么在这里没有看到类似的内存泄漏错误。有人可以帮助理解这种情况，无论我做错了什么。我使用的 Valgrind 命令是：
valgrind -v --tool=memcheck --leak-check=full --num-callers=40 ./ValgrindOutput
谢谢你。