Don’t set RUNPATH if it is the system search path - CMAKE_SKIP_RPATH

[heitbaum]

The following libevent commit forces RPATH ce8be23 on Linux.

With the cleanup of RPATH/RUNPATH in - LibreELEC/LibreELEC.tv#6094 - we are cleaning up incorrect and unnecessary RPATH/RUNPATH, we have used the CMAKE_SKIP_RPATH build option but given that libevent.so is in the system search path - the RUNPATH is unnecessary.

reading:

• https://gitlab.kitware.com/cmake/community/-/wikis/doc/cmake/RPATH-handling

Suggest that RUNPATH can still be used when installing, but only if it's not a system directory (as per the wiki) so that it is not necessary to use CMAKE_SKIP_RPATH

 # readelf --dynamic /usr/lib/libevent.so | grep '\['
 Addr: 0x000000000005fd48  Offset: 0x04fd48  Link to section: [ 2] '.dynstr'
  NEEDED            Shared library: [libc.so.6]
  SONAME            Library soname: [libevent-2.1.so.7]
  RUNPATH           Library runpath: [/usr/lib]

# LD_LIBRARY_PATH= LD_DEBUG=libs ldd -v /usr/lib/libevent.so 
    190127:     find library=libm.so.6 [0]; searching
    190127:      search cache=/etc/ld.so.cache
    190127:      search path=/usr/lib/tls/aarch64:/usr/lib/tls:/usr/lib/aarch64:/usr/lib                (system search path)
    190127:       trying file=/usr/lib/tls/aarch64/libm.so.6
    190127:       trying file=/usr/lib/tls/libm.so.6
    190127:       trying file=/usr/lib/aarch64/libm.so.6
    190127:       trying file=/usr/lib/libm.so.6
    190127:     
    190127:     find library=libc.so.6 [0]; searching
    190127:      search cache=/etc/ld.so.cache
    190127:      search path=/usr/lib           (system search path)
    190127:       trying file=/usr/lib/libc.so.6
    190127:     
    190127:     
    190127:     calling init: /lib/ld-linux-aarch64.so.1
    190127:     
    190127:     
    190127:     calling init: /usr/lib/libc.so.6
    190127:     
    190127:     
    190127:     calling init: /usr/lib/libm.so.6
    190127:     
    190127:     
    190127:     initialize program: /bin/bash
    190127:     
    190127:     
    190127:     transferring control: /bin/bash
    190127:     
ldd: $warning: you do not have execution permission for `/usr/lib/libevent.so'
    190131:     find library=libc.so.6 [0]; searching
    190131:      search path=/usr/lib/tls/aarch64:/usr/lib/tls:/usr/lib/aarch64:/usr/lib                (system search path)
    190131:       trying file=/usr/lib/tls/aarch64/libc.so.6
    190131:       trying file=/usr/lib/tls/libc.so.6
    190131:       trying file=/usr/lib/aarch64/libc.so.6
    190131:       trying file=/usr/lib/libc.so.6
    190131:     
        linux-vdso.so.1 (0x0000ffffbb324000)
        libc.so.6 => /usr/lib/libc.so.6 (0x0000ffffbb10d000)
        /usr/lib/ld-linux-aarch64.so.1 (0x0000ffffbb2f4000)

        Version information:
        /usr/lib/libevent.so:
                libc.so.6 (GLIBC_2.17) => /usr/lib/libc.so.6
                libc.so.6 (GLIBC_2.25) => /usr/lib/libc.so.6
                libc.so.6 (GLIBC_2.33) => /usr/lib/libc.so.6
        /usr/lib/libc.so.6:
                ld-linux-aarch64.so.1 (GLIBC_PRIVATE) => /usr/lib/ld-linux-aarch64.so.1
                ld-linux-aarch64.so.1 (GLIBC_2.17) => /usr/lib/ld-linux-aarch64.so.1

[azat]

Thanks for the detailed report, fixed (Now RPATH will not be installed for when libevent is installed into system wide directories).

[heitbaum]

Hi @azat - tested the patch in our build tree. Works as expected 👍. Thanks.