如何在 Mac OS X (C++) 中使用 dylib

How to use dylib in Mac OS X (C++)(如何在 Mac OS X (C++) 中使用 dylib)

问题描述

我制作了一个应用程序(一个可执行文件)成功调用了一些 dylib.但是，dylib 文件和可执行文件位于不同的目录中.我将包含 dylib 文件的目录添加到 $PATH 环境变量中.但是，它仍然无法加载.我将所有 dylib 文件复制到可执行文件中，程序终于运行了.这证实了 dylib 文件没有问题.但是，我如何告诉操作系统找到它?
在windows中，我只需要将包含dll文件的目录路径添加到$PATH.我需要为 Mac OS X 做什么?

I made an application (an executable) calling some dylib successfully. However, the dylib files and the executable are in different directory. I added the directory contains dylib files to the $PATH environment variable. However, it still doesn't load. I copy all the dylib files to the executable, the program finally runs. This confirms the dylib files have no problem. However, how can I tell the OS to find it?
In windows, I just need to add the directory path contains dll files to $PATH. What do I need to do for Mac OS X?

推荐答案

在阅读 Justin 提供的链接后，我成功地使用 @executable_path 令牌将我的 dylib install_name 更改为指向与我的可执行文件所在的目录相同.

After reading the link that Justin provided, I was successfully able to use the @executable_path token to change my dylib install_name to point to the same dir where my executable is located.

@executable_path 绝对路径很烦人.有时您想将框架嵌入到应用程序中，而不必安装将框架放入/Library 或类似位置.

@executable_path Absolute paths are annoying. Sometimes you want to embed a framework into an application instead of having to install the framework into /Library or a similar location.

Mac 对此的解决方案是@executable_path.这是一个神奇的令牌当放在库安装名称的开头时，会得到扩展到加载它的可执行文件的路径，减去最后一个组件.例如，假设 Bar.app 链接到Foo.framework.如果 Bar.app 安装在/Applications 中，@executable_path 将扩展到/Applications/Bar.app/Contents/MacOS.如果您打算在 Contents/Frameworks 中嵌入框架，那么您可以将 Foo.framework 的安装名称设置为@executable_path/../Frameworks/Foo.framework/Versions/A/Foo.这动态链接器会将其扩展为/Applications/Bar.app/Contents/MacOS/../Frameworks/Foo.framework/Versions/A/Foo并会在那里找到框架.

The Mac's solution to this is @executable_path. This is a magic token that, when placed at the beginning of a library's install name, gets expanded to the path of the executable that's loading it, minus the last component. For example, let's say that Bar.app links against Foo.framework. If Bar.app is installed in /Applications, @executable_path will expand to /Applications/Bar.app/Contents/MacOS. If you intend to embed the framework in Contents/Frameworks, then you can just set Foo.framework's install name to @executable_path/../Frameworks/Foo.framework/Versions/A/Foo. The dynamic linker will expand that to /Applications/Bar.app/Contents/MacOS/../Frameworks/Foo.framework/Versions/A/Foo and will find the framework there.

http://www.mikeash.com/pyblog/friday-qa-2009-11-06-linking-and-install-names.html

我会用一个例子来演示.

I will demonstrate with an example.

假设我有以下可执行文件 /opt/local/bin/convert，其动态库位于 /opt/local/lib 中.我想将它复制到另一个目录，并让它从与我复制可执行文件的目录相同的目录加载它的 dylib.

Let's say I have the following executable /opt/local/bin/convert and its dylibs are in /opt/local/lib. I want to copy it to another dir and have it load its dylibs from the same directory as where I copied the executable.

> mkdir ~/tmp/bin
> cp /opt/local/bin/convert ~/tmp/bin

获取可执行文件 dylibs 的列表

Get a list of the executables dylibs

> otool -L ~/tmp/bin/convert
~/tmp/bin/convert:
    /opt/local/lib/libtiff.3.dylib (compatibility version 13.0.0, current version 13.5.0)
    /usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 159.1.0)
    /opt/local/lib/libjpeg.8.dylib (compatibility version 12.0.0, current version 12.0.0)
    /opt/local/lib/libfontconfig.1.dylib (compatibility version 6.0.0, current version 6.4.0)
    /opt/local/lib/libiconv.2.dylib (compatibility version 8.0.0, current version 8.1.0)
    /opt/local/lib/libfreetype.6.dylib (compatibility version 15.0.0, current version 15.0.0)
    /opt/local/lib/libexpat.1.dylib (compatibility version 7.0.0, current version 7.2.0)
    /opt/local/lib/libbz2.1.0.dylib (compatibility version 1.0.0, current version 1.0.6)
    /opt/local/lib/libz.1.dylib (compatibility version 1.0.0, current version 1.2.6)
    ...

我只关心 /opt/local/lib 目录中的 dylib，所以我们只提取 /opt 中的 dylib.我想保持所有其他 dylib 引用完整无缺，尤其是对 /usr/lib/libSystem 的东西.

I only care about the dylibs in the /opt/local/lib dir, so we pull out only dylibs in /opt. I want to keep all other dylib references intact especially to /usr/lib/libSystem stuff.

> DYLIBS=`otool -L ~/tmp/bin/convert | grep "/opt" | awk -F' ' '{ print $1 }'`

将可执行文件引用的所有 dylib 复制到可执行文件复制到的同一目录.

Copy all the dylibs that the executable references to the same dir where the executable has been copied to.

> for dylib in $DYLIBS; do cp $dylib ~/tmp/bin/; done;

使用install_name_tool 更改我们在上述步骤中提取的所有 dylib 的安装名称，并通过在 dylib 名称前添加 @executable_path 来替换它们.这将使动态链接器在可执行文件所在的同一目录中查找 dylib.

Use the install_name_tool to change the install name of all the dylibs we pulled out in the step above, and replace them by prepending the @executable_path to the dylib name. This will make the dynamic linker look for the dylib in the same directory as where the executable is located.

> for dylib in $DYLIBS; do install_name_tool -change $dylib @executable_path/`basename $dylib` ~/tmp/bin/convert; done;

确认安装名称已更改并且 libSystem 仍指向 /usr/lib/libSystem.

Confirm that the install names have been changed and that libSystem is still pointing to /usr/lib/libSystem.

> otool -L ~/tmp/bin/convert
~/tmp/bin/convert:
    @executable_path/libtiff.3.dylib (compatibility version 13.0.0, current version 13.5.0)
    /usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 159.1.0)
    @executable_path/libjpeg.8.dylib (compatibility version 12.0.0, current version 12.0.0)
    @executable_path/libfontconfig.1.dylib (compatibility version 6.0.0, current version 6.4.0)
    @executable_path/libiconv.2.dylib (compatibility version 8.0.0, current version 8.1.0)
    @executable_path/libfreetype.6.dylib (compatibility version 15.0.0, current version 15.0.0)
    @executable_path/libexpat.1.dylib (compatibility version 7.0.0, current version 7.2.0)
    @executable_path/libbz2.1.0.dylib (compatibility version 1.0.0, current version 1.0.6)
    @executable_path/libz.1.dylib (compatibility version 1.0.0, current version 1.2.6)
    ...

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