问题描述

我正在使用名为 ohNet 的框架构建应用程序.构建框架后，可以通过 make install 安装框架.默认情况下，这些库安装在 /usr/local/[lib|include] 文件夹中.好的.

我正在使用 Eclipse 进行开发.为了使用这个库，我必须设置库的包含路径(在本例中为 usr/local/include/ohNet)，设置链接器搜索路径 (-L)(/usr/local/lib/ohNet) 和特定的库 (-l).当我在 Eclipse 中构建项目时，它工作正常，但是如果我尝试运行该程序，我将面临以下消息:

加载共享库时出错:libohNet.so:无法打开共享对象文件:没有这样的文件或目录

我已经仔细检查过，文件 libohNet.so 就在这个目录中！找不到这个文件是什么原因?

我在google上搜索，发现一些帖子，说库安装到/usr/local/lib而不是/usr/lib是有问题的看这里 ...我是否必须在 eclipse 中配置一些其他设置以使 ld 识别此路径中的库?有什么办法解决这个问题?

问候

这是运行时错误，不是构建错误.设置 -L 标志对运行时链接器没有任何作用.您需要做的是告诉运行时加载程序也在/usr/local/lib 中查找库.你可以通过两种方式做到这一点.首先是添加LD_LIBRARY_PATH环境变量的路径:

二是更新运行时链接器的配置文件.这可以在/etc/ld.so.conf 文件中发生，方法是:

在该文件的某个位置，或者通过在包含新路径的/etc/ld.so.conf.d/目录中创建一个新的 *.conf 文件.例如:

只需:

在里面.这是这样做的推荐方式，因为它允许您将自定义库路径与系统设置的路径分开.(99"前缀是为了确保文件与那里的其他文件相比最后加载，这样它就不会抢占可能包含相同库的系统路径.)

在/etc中修改/创建文件后，需要运行:

以 root 身份使更改生效.(此命令更新/etc/ld.so.cache 文件，这是运行时链接器使用的实际文件.)

二进制文件还有另一种方法可以在运行时找到所需的库.您实际上可以将库路径硬编码到可执行文件本身中.这是通过设置所谓的rpath"来实现的.这是一个链接器选项，必须从 gcc(或 g++)传递到链接器，因此必须使用 -Wl 选项.链接器选项是 -rpath=PATH.因此，您需要将其添加到您的链接标志中:

不过，我不建议您这样做.当您将库与可执行文件(可能带有安装程序)以及相对 rpath(使用 rpath $ORIGIN 功能)或绝对路径(当您安装在/opt，例如)然后用于在运行时查找那些捆绑的库.

I am building an application using a framework called ohNet. After building the framework, there is the possibility to install the framework via make install. By default the libraries are installed inside the /usr/local/[lib|include] folders. ok.

I am using eclipse for development. In order to use this libraries I have to set the include path to the library (in this case usr/local/include/ohNet), set the Linker search path (-L)(/usr/local/lib/ohNet) and specific libraries (-l) (in this case i choose a library called libohNet.so which is in this folder. When I build the project in eclipse it works fine, however if i try to run the programm i am faced with the following message:

error while loading shared libraries: libohNet.so: cannot open shared object file: No such file or directory

I've double checked this, and the file libohNet.so is in this directory! What's the reason that this file cannot be found?

I searched on google and found some posts, saying that it is problematic that libraries are getting installed into /usr/local/lib instead of /usr/lib see here ... Do I have to configure some additional settings in eclipse to make ld recognize libraries in this path? What's the solution for this?

regards

This is a runtime error, not a build error. Setting the -L flag does nothing for the runtime linker. What you need to do is to tell the runtime loader to also look in /usr/local/lib for libraries. You can do that in two ways. The first is to add the path to the LD_LIBRARY_PATH environment variable:

export LD_LIBRARY_PATH="$LD_LIBRARY_PATH:/usr/local/lib"

The second is to update the configuration file of the runtime linker. This can happen either in the /etc/ld.so.conf file, by putting the line:

/usr/local/lib

somewhere in that file, or by creating a new *.conf file in the /etc/ld.so.conf.d/ directory that contains the new path. For example:

/etc/ld.so.conf.d/99local.conf

with just:

/usr/local/lib

in it. This is the recommended way of doing this, as it allows you to keep your custom library paths separate from paths set by the system. (The "99" prefix is there to make sure the file is loaded last compared to other files there, so that it won't preempt system paths that could contain the same libraries.)

After you modify/create the file in /etc, you need to run:

ldconfig

as root for the change to take effect. (This command updates the /etc/ld.so.cache file, which is the actual file used by the runtime linker.)

There's also another way for a binary to find needed libraries at runtime. You can actually hard-code library paths into the executable itself. This is accomplished by setting a so called "rpath". This is a linker option and must be passed from gcc (or g++) to the linker, so the -Wl option has to be used. The linker option is -rpath=PATH. So you would need to add this to your link flags:

-Wl,-rpath=/usr/local/lib

I don't recommend this for your case though. An rpath is useful when you're shipping libraries together with your executable (maybe with an installer), and a relative rpath (using the rpath $ORIGIN feature) or absolute one (for when you install in /opt, for example) is then used to find those bundled libs at runtime.

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