为什么lldb不再转发我的环境变量? [英] Why doesn't lldb forward my environment variable anymore?

问题描述

我正在为FFmpeg制作补丁程序，需要调试我的代码.我正在加载一个外部库，并且为了测试不同的库版本，我将它们放在不同的文件夹中.要选择我要使用的那个，我一直在使用DYLD_LIBRARY_PATH=/path/to/lib/dir ./ffmpeg，它可以正常工作.但是，当我在lldb中尝试它时，它会崩溃，提示dyld: Library not loaded和Reason: image not found.以前可以在Xcode 7.1之前运行，但是我最近才进行了升级，因此它停止了工作.

I'm working on a patch for FFmpeg and need to debug my code. I'm loading an external library, and in order to test different library versions, I have them in different folders. To select which one I want to use, I've been using DYLD_LIBRARY_PATH=/path/to/lib/dir ./ffmpeg and that works okay. But when I try it within lldb, it crashes saying dyld: Library not loaded and Reason: image not found. This used to work pre-Xcode 7.1, but I just recently upgraded and it stopped working.

这是我的MVCE:

#include <stdio.h>
#include <stdlib.h>

int main() {
  char* str = getenv("DYLD_LIBRARY_PATH");
  if (str) puts(str);
  else     puts("(null)");
  return 0;
}

按以下方式运行该程序会产生输出:

Running this program as follows produces the output:

$ ./a.out
(null)
$ DYLD_LIBRARY_PATH=/tmp ./a.out
/tmp

这看起来还不错.但是当我尝试使用lldb时，它会失败:

That looks okay. But when I try to use lldb it fails:

$ DYLD_LIBRARY_PATH=/tmp lldb ./a.out
(lldb) target create "./a.out"
Current executable set to './a.out' (x86_64).
(lldb) run
Process 54255 launched: './a.out' (x86_64)
(null)
Process 54255 exited with status = 0 (0x00000000)

尝试在lldb中设置环境变量的工作原理:

Trying to set the environment variable inside lldb works:

lldb ./a.out
(lldb) target create "./a.out"
Current executable set to './a.out' (x86_64).
(lldb) env DYLD_LIBRARY_PATH=/tmp
(lldb) run
Process 54331 launched: './a.out' (x86_64)
/tmp
Process 54331 exited with status = 0 (0x00000000) 

lldb版本(来自Xcode 7.1):

lldb version (it's from Xcode 7.1):

$ lldb --version
lldb-340.4.110

问题:这是否是预期的新功能"，或者这是lldb中的新错误(或者我完全疯了，而且从未使用过)?我非常肯定lldb用来转发DYLD_LIBRARY_PATH环境变量，所以它怎么了?

Question: Is this an intended new "feature," or is this a new bug in lldb (or am I totally crazy and this never used to work)? I'm quite positive lldb used to forward the DYLD_LIBRARY_PATH environment variable, so how come it isn't anymore?

这是在OS X 10.11.1.上

This is on OS X 10.11.1.

推荐答案

如果在El Capitan(OS X 10.11)上使用，则几乎可以肯定是系统完整性保护的副作用.来自系统完整性保护指南:运行时保护文章:

If this is on El Capitan (OS X 10.11), then it's almost certainly a side effect of System Integrity Protection. From the System Integrity Protection Guide: Runtime Protections article:

启动进程时，内核检查以查看是否主进程 可执行文件受磁盘保护或使用特殊系统签名 权利.如果任何一个为真，则设置一个标志来表示它 保护免受修改. …

When a process is started, the kernel checks to see whether the main executable is protected on disk or is signed with an special system entitlement. If either is true, then a flag is set to denote that it is protected against modification. …

…任何动态链接器(dyld) 在以下情况下清除环境变量，例如DYLD_LIBRARY_PATH 启动受保护的进程.

… Any dynamic linker (dyld) environment variables, such as DYLD_LIBRARY_PATH, are purged when launching protected processes.

/usr/bin中的所有内容都以这种方式受到保护.因此，当您调用/usr/bin/lldb时，将清除所有DYLD_ *环境变量.

Everything in /usr/bin is protected in this fashion. Therefore, when you invoke /usr/bin/lldb, all DYLD_* environment variables are purged.

应该可以从Xcode.app或命令行工具中运行lldb，如下所示:

It should work to run lldb from within Xcode.app or the Command Line Tools, like so:

DYLD_LIBRARY_PATH=whatever /Applications/Xcode.app/Contents/Developer/usr/bin/lldb <whatever else>

我认为lldb的副本不受保护. /usr/bin/lldb实际上只是一个蹦床，可以在Xcode或命令行工具中执行该版本，因此最终您将运行相同的东西.但是/usr/bin/lldb受保护，因此在运行时会清除DYLD_ *环境变量.

I don't believe that copy of lldb is protected. /usr/bin/lldb is actually just a trampoline that executes the version in Xcode or the Command Line Tools, so you're ultimately running the same thing. But /usr/bin/lldb is protected so the DYLD_* environment variables are purged when running that.

否则，您将必须在lldb中设置环境变量，如

Otherwise, you will have to set the environment variable inside lldb as shown in this thread:

(lldb) process launch --environment DYLD_LIBRARY_PATH=<mydylibpath> -- arg1 arg2 arg3

或使用简短的-v选项:

or using the short -v option:

(lldb) process launch -v DYLD_LIBRARY_PATH=<mydylibpath> -- arg1 arg2 arg3

或者，您可以禁用系统完整性保护，尽管它有很好的用途.

Or, you can disable System Integrity Protection, although it serves a good purpose.

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