Valgrind没有显示任何分配

我正在学习Rust而且我正在玩 Box ，所以我尝试使用 valgrind 检查泄漏，但它显示堆上没有分配：

$ rustc -C opt-level=0 raii.rs
$ valgrind ./raii
==3850== Memcheck, a memory error detector
==3850== Copyright (C) 2002-2013, and GNU GPL'd, by Julian Seward et al.
==3850== Using Valgrind-3.10.1 and LibVEX; rerun with -h for copyright info
==3850== Command: ./raii
==3850== 
5
Changed:10
==3850== 
==3850== HEAP SUMMARY:
==3850==     in use at exit: 0 bytes in 0 blocks
==3850==   total heap usage: 0 allocs, 0 frees, 0 bytes allocated
==3850== 
==3850== All heap blocks were freed -- no leaks are possible
==3850== 
==3850== For counts of detected and suppressed errors, rerun with: -v
==3850== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)

valgrind --leak-check=full ./raii 显示exaclty相同的结果 .

这是Rust代码：

fn main() {
    let mut _box2 = Box::new(5i32);

    println!("{}", _box2);
    *_box2 = 10i32;
    println!("Changed:{}", _box2);

    {
        let _box3 = Box::new(4i32);
    }
}

其他一些信息：

$ rustc -V
rustc 1.8.0 (db2939409 2016-04-11)
$ valgrind --version
valgrind-3.10.1
$ uname -a
Linux 3.19.0-59-generic #65~14.04.1-Ubuntu SMP Tue Apr 19 18:57:09 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux

这是为什么？我以为 Box 在堆上分配变量 . 此外，this example显示几乎相同的代码，valgrind显示那里的分配 .

如果我添加以下代码：

let _stack = (1u64, 2u64, 3u64);
let _heap = Box::new((4u64, 5u64, 6u64));
println!("Memory used by stack: {} bytes", std::mem::size_of_val(&_stack));
println!("Memory used by heap: {} bytes", std::mem::size_of_val(&_heap));

它打印完全符合预期：

$ ./raii 
Memory used by stack: 24 bytes
Memory used by heap: 8 bytes

• 在第二种情况下，元组被放置在堆上，指针（8个字节）被推入堆栈，而在第一种情况下，元组被放置在堆栈上，因此需要24个字节 .

Valgrind似乎能够计算其他程序的堆分配：

$ valgrind echo "test"
==4575== Memcheck, a memory error detector
==4575== Copyright (C) 2002-2013, and GNU GPL'd, by Julian Seward et al.
==4575== Using Valgrind-3.10.1 and LibVEX; rerun with -h for copyright info
==4575== Command: echo test
==4575== 
test
==4575== 
==4575== HEAP SUMMARY:
==4575==     in use at exit: 0 bytes in 0 blocks
==4575==   total heap usage: 30 allocs, 30 frees, 3,681 bytes allocated
==4575== 
==4575== All heap blocks were freed -- no leaks are possible
==4575== 
==4575== For counts of detected and suppressed errors, rerun with: -v
==4575== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)