On 03/12/2014 13:13, Joachim Breitner wrote:
Hi,
Am Mittwoch, den 03.12.2014, 11:18 +0100 schrieb Herbert Valerio Riedel:
On 2014-12-03 at 09:48:58 +0100, Simon Peyton Jones wrote: For a non-failing linker_unload environment, the testprogram is linked against libgmp.so:
$ ldd tests/rts/linker_unload linux-vdso.so.1 => (0x00007fff20f6c000) libgmp.so.10 => /usr/lib/x86_64-linux-gnu/libgmp.so.10 (0x00007f83c5bbb000) libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007f83c58b5000) librt.so.1 => /lib/x86_64-linux-gnu/librt.so.1 (0x00007f83c56ac000) libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007f83c54a8000) libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f83c50e3000) libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007f83c4ec4000) /lib64/ld-linux-x86-64.so.2 (0x00007f83c5e76000)
and for a failing, it is not.
I further narrowed it down to the question of whether gcc passes "--as-needed" to ld by default: If I pass "-optl-Wl,--no-as-needed" to ghc when compiling linker_unload.c, it works there as well.
In some releases of Ubuntu, --as-needed is the default¹. Not sure why Herbert does not see this behavior in a recent release (14.04).
I’m also not sure about the right fix: Should we just pass -Wl,--no-as-needed to gcc always? But clearly there is a reason for this flag becoming default. Can we set up things so that they work with --as-needed?
No, I don't think we should do that. We should play nicely with however the platform decides it wants to do linking. Cheers, Simon