std::string内存布局

Security Classification: 【C-1】 | Publish Time:2024-02-20 | Category:Test Notes | Edit

Expiry Notice: The article was published three months ago. Please independently assess the validity of the technical methods and code mentioned within. :)

AI摘要:本文探讨了protobuf的`SerializeToString`返回值`std::string`的内存布局，展示了在不同编译环境下（CLion和Android Studio）观察到的内存布局差异。通过demo代码，展示了如何在`cout`处打断点并查看`std::string`的内存结构，发现其内存布局为【cap+size+data地址】的形式。文章附有多张内存布局的截图，以便于理解和比较。 --- (来自模型:gpt-4o-mini-2024-07-18)

## 前言

由于protobuf的SerializeToString返回值是std::string，在frida hook的工作中遇到了一些晦涩难懂的问题。需要去了解一下它的内存布局。

demo代码：

```cpp
#include <iostream>
using namespace std;

int main(){
    long bottom = -1;
    std::string buildId = "123123123123123123123123123123123123123123123123123123123123123123123123123123123123123123123123123123123123123123123123123123123123123123123123";
    cout << buildId <<endl;
}
```

## clion编译下的内存布局

使用clion观测，在cout此处打上断点：

![](https://p1.meituan.net/xianfu/948448105f388ee304360b20eb02eaa9314697.png%40watermark=1&&object=L3dkY2Zsb3cvN2RiN2M4NTFjYmVjZDg4MTM1OTZjMTYzOWE2MzQ4MDM0MjY0LnBuZw==&p=8&t=90&x=10&y=10)

使用memory查看 &buildId的内存布局

![](https://p0.meituan.net/xianfu/5023027fc0848c9b14e1e4bfc5468e68146642.png%40watermark=1&&object=L3dkY2Zsb3cvN2RiN2M4NTFjYmVjZDg4MTM1OTZjMTYzOWE2MzQ4MDM0MjY0LnBuZw==&p=8&t=90&x=10&y=10)

![](https://p0.meituan.net/xianfu/2fdba91f7d4928df9e63f679a7d80d00103659.png%40watermark=1&&object=L3dkY2Zsb3cvN2RiN2M4NTFjYmVjZDg4MTM1OTZjMTYzOWE2MzQ4MDM0MjY0LnBuZw==&p=8&t=90&x=10&y=10)

![](https://p0.meituan.net/xianfu/4c7d18258ea8b84b7efaf9276cd9f1fa156835.png%40watermark=1&&object=L3dkY2Zsb3cvN2RiN2M4NTFjYmVjZDg4MTM1OTZjMTYzOWE2MzQ4MDM0MjY0LnBuZw==&p=8&t=90&x=10&y=10)

## android studio编译下的内存布局

![](https://p1.meituan.net/xianfu/ce597865a71263c20887c6b66c4d6c96204688.png%40watermark=1&&object=L3dkY2Zsb3cvN2RiN2M4NTFjYmVjZDg4MTM1OTZjMTYzOWE2MzQ4MDM0MjY0LnBuZw==&p=8&t=90&x=10&y=10)

![](https://p1.meituan.net/xianfu/eb744c25e3f690d21adc1d7fb760e9bd100695.png%40watermark=1&&object=L3dkY2Zsb3cvN2RiN2M4NTFjYmVjZDg4MTM1OTZjMTYzOWE2MzQ4MDM0MjY0LnBuZw==&p=8&t=90&x=10&y=10)

可以看出是以【cap+size+data地址】的形式布局。

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std::string内存布局

© Copyright: This article is an original work and the copyright belongs to the Depy's docs unless marked as ReproducedPlease contact the blogger for authorization to reprint

© Copyright: This article is an original work and the copyright belongs to the Depy's docs unless marked as Reproduced

Please contact the blogger for authorization to reprint