C ++可疑堆栈溢出更改函数参数 [英] C++ Suspected stack overflow changing function parameters

问题描述

我正在使用 setcontext（）， makecontext（）在C ++中实现用户级线程库，在Linux系统上 getcontext（）和 swapcontext（）。

我使用一个包装函数来包装用户想要作为线程运行的函数。例如，用户调用 newthread（funcPtr），并且在线程库 funcPtr 中传递给包装器函数

错误的发生方式有所不同，取决于我是否在函数中启动了一个未使用的字符串。如果我包括行 string s =a; 程序将运行到完成，但 gdb 正在切换到字符串库中的某处。没有这一行，程序在离开函数包装之后就会出现错误。

输出 gdb 到 function（）。

我运行 valgrind 在输出中没有看到任何特别的异常，只是很多大小4的无效读取和大小4的写入无效警告，通常在C ++标准 map 。

解决方案

您也可以尝试 AddressSanitizer 进行调试。它可以检测堆栈缓冲区溢出。下面是如何在Linux上使用它：

AddressSanitizer至少需要gcc 4.8，并且必须安装libasan（例如Fedora上的 yum install libasan 为root）。编译并链接到 -g -fsanitize = address 并运行生成的可执行文件。 AddressSanitizer停止并发出信息，如果它检测到第一个错误，没有长日志文件需要分析。解决报告的问题，编译并再次运行，直到AddressSanitizer不再停止程序。不幸的是，可能会有误报，因为您在程序中使用swapcontext，但值得一试。通过添加属性no_sanitize_address可以关闭特定函数的工具： extern int func（void）__attribute __（（no_sanitize_address））;

I am working on implementing a user level thread library in C++ using setcontext(), makecontext(), getcontext(), and swapcontext() on a Linux system.

I am using a wrapper function to wrap the function the user wants to run as a thread. For example, the user calls newthread(funcPtr), and within the thread library funcPtr is passed to a wrapper function that runs it.

The error occurs differently depending on whether or not I initiate an unused string within the function. If I include the line string s = "a"; the program will run to completion, but gdb reveals that context is switching to somewhere within the string library. Without this line, the program segfaults after leaving the function wrapper.

The gdb output shows the corruption of the parameters to function().

I ran valgrind but did not see anything particularly out of the ordinary in the output, just many "Invalid read of size 4" and "Invalid write of size 4" warnings, usually within the C++ standard map.

解决方案

You could try also AddressSanitizer for debugging. It can detect stack buffer overflows. Here's how to use it on Linux:

At least gcc 4.8 is needed for AddressSanitizer and libasan must be installed (e.g. on Fedora yum install libasan as root). Compile and link with -g -fsanitize=address and run the generated executable. AddressSanitizer stops and emits information if it detects the first error, no long log files have to be analyzed. Solve the reported problem, compile and run again until AddressSanitizer doesn't stop the program anymore. Unfortunately there might be false positives because you use swapcontext in your program, but it's worth a try. Instrumentation can be turned off for a specific function by adding the attribute no_sanitize_address: extern int func(void) __attribute__((no_sanitize_address));

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