Re: Gnulib use of -Wl,-rpath

[Bruno Haible]

Hi,

Jeffrey Walton wrote:
> Second, here is a failed Gnulib runner. IDN's runner 3 does this:
> 
> libtool: link: gcc -g2 -O2 -fsanitize=address -fno-omit-frame-pointer
> -march=native -fPIC -pthread -fsanitize=address -Wl,-R
> -Wl,/var/sanitize/lib64 -Wl,--enable-new-dtags -o tst_tld tst_tld.o
> -Wl,--no-as-needed  -L/var/sanitize/lib64 libutils.a
> ../lib/.libs/libidn.so ../gl/.libs/libgnu.a -ldl -lpthread -pthread
> -Wl,-rpath -Wl,/home/build/libidn-1.35/lib/.libs -Wl,-rpath
> -Wl,/var/sanitize/lib64
> gmake[2]: Leaving directory '/home/build/libidn-1.35/tests'
> gmake  check-TESTS
> gmake[2]: Entering directory '/home/build/libidn-1.35/tests'
> gmake[3]: Entering directory '/home/build/libidn-1.35/tests'
> FAIL: tst_stringprep
> FAIL: tst_punycode
> ...

In these cases, the following tools are useful (on ELF systems):
  - ldd BINARY
    which tells you how the runtime linker resolves the shared libraries
    in the current situation,
  - objdump -p BINARY | grep '\(NEEDED\|RPATH\|RUNPATH\)'
    which tells you what information is encoded in the binary for the
    runtime linker,
  - readelf -d BINARY | grep '\(NEEDED\|RPATH\|RUNPATH\)'
    likewise.

> As I understand things an RPATH cannoth be overridden by
> LD_LIBRARY_PATH, while a RUNPATH can be overridden by a
> LD_LIBRARY_PATH.

At least that's what [1] says. See also [2].

> In the failed run, notice two things.
> 
> (1) my LDFLAGS (Wl,-R -Wl,/var/sanitize/lib64 -Wl,--enable-new-dtags)
> got overridden by Gnulib's LDFLAGS (-Wl,-rpath
> -Wl,/var/sanitize/lib64).

They get combined, not overridden. Multiple -R or -rpath options are
cumulative.

Did you also try -Wl,--disable-new-dtags instead of -Wl,--enable-new-dtags?
What is the outcome? Do the tests pass or fail?

> (2) Gnulib's path does not include /home/build/libidn-1.35/gl/.libs,
> which is where Gnulib is located

Yes, the LD_LIBRARY_PATH gets set in wrapper scripts that libtool
installs in the build tree, outside the .lib directories.

> My question are,
> 
> (1) why id Gnulib using a rpath instead of a runpath?

The question (raised by [2]) is more: Why are some distros using a runpath
instead of an rpath, breaking 20 years of existing practice (see [3][5]
and [4])?

> (2) why is Gnulib omitting <locations>/gl/.libs frm the runpath?

Answered above.

> (3) why are runpaths being set for a static archive?

This option has no effect on static archives, I guess. Please verify this
using 'objdump' (see above).

Bruno

[1] https://news.ycombinator.com/item?id=14222349
[2] 
https://stackoverflow.com/questions/52018092/how-to-set-rpath-and-runpath-with-gcc-ld
[3] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=847298
[4] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=859732
[5] https://bugs.launchpad.net/ubuntu/+source/eglibc/+bug/1253638