Question

使用gcc运行-Wl,--verbose会打印

之类的内容

attempt to open /foo/gcc-6.3.0/lib64/../lib64/libm.so failed
attempt to open /foo/gcc-6.3.0/lib64/../lib64/libm.a failed
attempt to open /foo/gcc-6.3.0/lib/x86_64-redhat-linux/6.3.0/libm.so failed
attempt to open /foo/gcc-6.3.0/lib/x86_64-redhat-linux/6.3.0/libm.a failed
attempt to open /foo/gcc-6.3.0/lib/../lib64/libm.so failed
attempt to open /foo/gcc-6.3.0/lib/../lib64/libm.a failed
attempt to open /foo/gcc-6.3.0/lib/gcc/x86_64-redhat-linux/6.3.0/libm.so failed
attempt to open /foo/gcc-6.3.0/lib/gcc/x86_64-redhat-linux/6.3.0/libm.a failed
attempt to open /foo/gcc-6.3.0/lib/gcc/x86_64-redhat-linux/6.3.0/../../../x86_64-redhat-linux/6.3.0/libm.so failed
attempt to open /foo/gcc-6.3.0/lib/gcc/x86_64-redhat-linux/6.3.0/../../../x86_64-redhat-linux/6.3.0/libm.a failed
attempt to open /foo/gcc-6.3.0/lib/gcc/x86_64-redhat-linux/6.3.0/../../../../lib64/libm.so failed
attempt to open /foo/gcc-6.3.0/lib/gcc/x86_64-redhat-linux/6.3.0/../../../../lib64/libm.a failed
attempt to open /lib/../lib64/libm.so failed
attempt to open /lib/../lib64/libm.a failed
attempt to open /usr/lib/../lib64/libm.so succeeded

这些路径是否需要在其中包含一堆../？例如，为什么/foo/gcc-6.3.0/lib64/../lib64/libm.so不仅仅是/foo/gcc-6.3.0/lib64/libm.so？此外，一些较长的路径扩展到相同的东西，例如， /foo/gcc-6.3.0/lib/gcc/x86_64-redhat-linux/6.3.0/../../../../lib64/libm.so和/foo/gcc-6.3.0/lib/../lib64/libm.so。

此外，明显缺少/foo/gcc-6.3.0/lib，而大多数库都安装在lib而不是lib64。

Answer 1

我在这里发现了两个类似的问题：

Why does g++ look in LIBRARY_PATH/../lib64 and where is this documented?

g++ searches /lib/../lib/, then /lib/

评论here阐明了决定这些路径形成的方式。

然而，这些并没有回答为什么使用这么多路径，即使它们解析到同一目录。

Answer 2

/foo/gcc-*中的库由gcc-*个包提供，这是/lib64/或/lib中提供的实际库的符号链接。

这些符号链接为gcc提供了有针对性的支持。

实际的库包含共享库。

以gcc-objc为例，以及它所指向的库libobjc。

$ rpm -ql gcc-objc
<snip>
/usr/lib/gcc/x86_64-redhat-linux/4.4.4/include/objc/thr.h
/usr/lib/gcc/x86_64-redhat-linux/4.4.4/include/objc/typedstream.h
/usr/lib/gcc/x86_64-redhat-linux/4.4.4/libobjc.a
/usr/lib/gcc/x86_64-redhat-linux/4.4.4/libobjc.so
/usr/lib/gcc/x86_64-redhat-linux/4.4.7
<snip>

$ ls -l /usr/lib/gcc/x86_64-redhat-linux/4.4.4/libobjc.so
/usr/lib/gcc/x86_64-redhat-linux/4.4.4/libobjc.so -> ../../../../lib64/libobjc.so.2

$ rpm -ql libobjc
/usr/lib64/libobjc.so.2
/usr/lib64/libobjc.so.2.0.0

现在让我们看看这些软件包的描述。

$ rpm -qi gcc-objc
gcc-objc provides Objective-C support for the GCC.
Mainly used on systems running NeXTSTEP, Objective-C is an
object-oriented derivative of the C language.

$ rpm -qi libobjc
This package contains Objective-C shared library which is needed to run
Objective-C dynamically linked programs.

奇怪的gcc链接器搜索路径

2 个答案: