问题
When building a binary or library, specifying the rpath
, i.e.
-Wl,rpath,<path/to/lib>
tells the linker where to find the required library at runtime of the binary.
What is the UNIX philosphy regarding absolute and relative paths here? Is it better to use an absolute path so the lib can be found from everywhere? Or is it better to make it relative so copying an entire directory or renaming a higher level path won't render the binary unusable?
Update
Using $ORIGIN
is usually the preferred way of building binaries. For libraries I like to put in the absolute path, because otherwise you won't be able to link to the library. A symbolic link will change the $ORIGIN
to point to the path of the link and not of the link target.
回答1:
What is the UNIX philosphy regarding absolute and relative paths here?
Using relative path makes an executable that only works when invoked from a particular directory, which is almost never what you want. E.g. if the executable is in /app/foo/bin/exe
and has DT_RUNPATH
of lib/
, and a dependent library is in /app/foo/lib/libfoo.so
, then the exe
would only run when invoked from /app/foo
, and not when invoked from any other directory.
Using absolute path is much better: you can do cd /tmp; /app/foo/bin/exe
and have the executable still work. This is still however less than ideal: you can't easily have multiple versions of the binary (important during development), and you dictate to end-users where they must install the package.
On systems that support $ORIGIN
, using DT_RUNPATH
of $ORIGIN/../lib
would give you an executable what works when installed anywhere and invoked from any directory, so long as relative paths to bin/
and lib/
are preserved.
回答2:
In the case of rpath
, it makes no sense to use a relative path, since a relative path will be relative to the current working directory, NOT relative to the directory where the binary/library was found. So it simply won't work for executables found in $PATH
or libraries in pretty much any case.
Instead, you can use the $ORIGIN
"special" path to have a path relative to the executable with-Wl,-rpath,'$ORIGIN'
-- note that you need quotes around it to avoid having the shell interpret it as a variable, and if you try to do this in a Makefile, you need $$
to avoid having make interpret the $
as well.
来源:https://stackoverflow.com/questions/38058041/correct-usage-of-rpath-relative-vs-absolute