【问题标题】：Why does Valgrind not detect a memory leak in a Rust program using nightly 1.29.0?为什么 Valgrind 在使用 nightly 1.29.0 的 Rust 程序中没有检测到内存泄漏？
【发布时间】：2019-01-01 16:58:29
【问题描述】：

我正在尝试在 this blog post 之后使用 Valgrind 检测 Rust 程序中的内存泄漏。我的源代码很简单：

#![feature(alloc_system)]
extern crate alloc_system;

use std::mem;

fn allocate() {
    let bad_vec = vec![0u8; 1024*1024];
    mem::forget(bad_vec);
}

fn main() {
    allocate();
}

我希望对 mem::forget() 的调用会产生内存泄漏，Valgrind 将能够处理该泄漏。但是，当我运行 Valgrind 时，它报告说不可能发生泄漏：

[memtest]> cargo run
   Compiling memtest v0.1.0 (file:///home/icarruthers/memtest)
    Finished dev [unoptimized + debuginfo] target(s) in 0.28s
     Running `target/debug/memtest`
[memtest]> valgrind target/debug/memtest
==18808== Memcheck, a memory error detector
==18808== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al.
==18808== Using Valgrind-3.11.0 and LibVEX; rerun with -h for copyright info
==18808== Command: target/debug/memtest
==18808== 
==18808== 
==18808== HEAP SUMMARY:
==18808==     in use at exit: 0 bytes in 0 blocks
==18808==   total heap usage: 0 allocs, 0 frees, 0 bytes allocated
==18808== 
==18808== All heap blocks were freed -- no leaks are possible
==18808== 
==18808== For counts of detected and suppressed errors, rerun with: -v
==18808== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)

我升级到最新的 nightly (1.29.0-nightly (6a1c0637c 2018-07-23))。

我错过了什么？

【问题讨论】：

标签： rust valgrind

【解决方案1】：

锈 1.32

从 Rust 1.32 开始，可执行文件的默认分配器是now the system allocator，因此您无需默认设置任何内容。

以前的版本

您没有正确使用全局分配器设置。这是一个nightly 功能，这意味着它随时可能发生变化。您的博文已过期。

查看module docs for std::alloc 以查看正确用法：

#![feature(alloc_system)]
extern crate alloc_system;

#[global_allocator]
static GLOBAL: alloc_system::System = alloc_system::System;

use std::mem;

fn allocate() {
    let bad_vec = vec![0u8; 1024*1024];
    mem::forget(bad_vec);
}

fn main() {
    allocate();
}

root@3fb431791293:/tmp/vg# valgrind target/debug/vg
==6326== Memcheck, a memory error detector
==6326== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al.
==6326== Using Valgrind-3.11.0 and LibVEX; rerun with -h for copyright info
==6326== Command: target/debug/vg
==6326==
==6326==
==6326== HEAP SUMMARY:
==6326==     in use at exit: 1,048,576 bytes in 1 blocks
==6326==   total heap usage: 12 allocs, 11 frees, 1,050,753 bytes allocated
==6326==
==6326== LEAK SUMMARY:
==6326==    definitely lost: 1,048,576 bytes in 1 blocks
==6326==    indirectly lost: 0 bytes in 0 blocks
==6326==      possibly lost: 0 bytes in 0 blocks
==6326==    still reachable: 0 bytes in 0 blocks
==6326==         suppressed: 0 bytes in 0 blocks
==6326== Rerun with --leak-check=full to see details of leaked memory
==6326==
==6326== For counts of detected and suppressed errors, rerun with: -v
==6326== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)

【讨论】：