By running "readelf -d " I have recently become aware
that the Debian Buster linker automatically turns all rpath requests
into runpath, and that runpath versus rpath difference apparently
creates some issues I am trying to debug for the PLplot OCaml binding
that did not appear for my previous (Debian Jessie) platform. (Note,
that our ocaml binding implements its language support in a primitive
way using add_custom_command and add_custom_target because as far as I
know there is no OCaml language support in upstream CMake.) These
runpath issues only show up for the PLplot build-tree configuration
that links all PLplot components statically, but note that external
libraries (such as libLASi, see below) are still linked as shared
for this case.
CMake does the right thing in the build tree for the corresponding C
example (with obviously good CMake language support for C) so I need
some help in figuring out what goes on there so that I can also do the
right thing for OCaml. (Note for the PLplot static build, the PLplot
libraries and C executables are all built using the PUBLIC signature
of target_link_libraries to force transitive linking in this (static)
case.)
The reason I have to be concerned about runpath is one of those external
libraries
(libLASi) is locally built and installed in a non-standard location
so we have this situation for it:
software@merlin> readelf -d /home/software/lasi_svn/install/lib/libLASi.so
|grep -Ei 'needed|path'
0x0001 (NEEDED) Shared library: [libpangoft2-1.0.so.0]
0x0001 (NEEDED) Shared library: [libfontconfig.so.1]
0x0001 (NEEDED) Shared library: [libpango-1.0.so.0]
0x0001 (NEEDED) Shared library: [libgobject-2.0.so.0]
0x0001 (NEEDED) Shared library: [libglib-2.0.so.0]
0x0001 (NEEDED) Shared library: [libfreetype.so.6]
0x0001 (NEEDED) Shared library: [libstdc++.so.6]
0x0001 (NEEDED) Shared library: [libm.so.6]
0x0001 (NEEDED) Shared library: [libgcc_s.so.1]
0x0001 (NEEDED) Shared library: [libc.so.6]
0x001d (RUNPATH)Library runpath:
[/home/software/lasi_svn/install/lib]
In a PLplot C example, the result of a build that was completely automated by
CMake (with
no mention of rpath in our build system for this PLplot static library case) is
as follows:
software@merlin> readelf -d examples/c/x01c |grep -Ei 'needed|path'
0x0001 (NEEDED) Shared library: [libLASi.so.2]
0x0001 (NEEDED) Shared library: [libpangoft2-1.0.so.0]
0x0001 (NEEDED) Shared library: [libpango-1.0.so.0]
0x0001 (NEEDED) Shared library: [libgobject-2.0.so.0]
0x0001 (NEEDED) Shared library: [libglib-2.0.so.0]
0x0001 (NEEDED) Shared library: [libfontconfig.so.1]
0x0001 (NEEDED) Shared library: [libfreetype.so.6]
0x0001 (NEEDED) Shared library: [libshp.so.2]
0x0001 (NEEDED) Shared library: [libqhull.so.7]
0x0001 (NEEDED) Shared library: [libm.so.6]
0x0001 (NEEDED) Shared library: [libstdc++.so.6]
0x0001 (NEEDED) Shared library: [libgcc_s.so.1]
0x0001 (NEEDED) Shared library: [libc.so.6]
0x001d (RUNPATH)Library runpath:
[/home/software/lasi_svn/install/lib]
And the reason for that RUNPATH line was the combination of CMake building
this example using the option -Wl,-rpath,/home/software/lasi_svn/install/lib and
Debian Testing transmuting that rpath request to runpath.
So all is well with that C example, but I would like to know *how*
CMake knew (for the build tree case) that the rpath option was needed.
That information is not available for any of the PLplot static
libraries in this case, and I also cannot find any mention of rpath in
our build system logic for this static case. So assuming I haven't
missed something in the PLplot build system, I am pretty sure that
CMake automatically detected that libLASi itself had RUNPATH set, but
if that is true, how did it detect that? For example, does CMake use
something like "readelf -d |grep -i path" for all
dependent shared libraries to figure this out, or is there an easier
way?
Once I get that information, then I will attempt to do something similar for the
corresponding OCaml example(s) where the current readelf result is
software@merlin> readelf -d examples/ocaml/x01ocaml |grep -Ei 'needed|path'
0x0001 (NEEDED) Shared library: [libLASi.so.2]
0x0001 (NEEDED) Shared library: [libpangoft2-1.0.so.0]
0x0001 (NEEDED) Shared library: [libpango-1.0.so.0]
0x0001 (
