ld.gold: relocation R_386_GOTOFF against preemptible symbol cannot be used when making a shared object

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Marco Leise (@mleise) reported this on 2018-04-25T12:45:53Z

Transferred from https://issues.dlang.org/show_bug.cgi?id=18798

CC List

• Walter Bright (@WalterBright)

Description

When linking a 32-bit shared library with dmd and ld.gold on Linux the linker bails out with:

/usr/x86_64-pc-linux-gnu/bin/ld: error: libgtkd-3.o: relocation R_386_GOTOFF against preemptible symbol _D3gtk9UIManagerQk9getWidgetMFAyaZCQBh6WidgetQh cannot be used when making a shared object
/usr/x86_64-pc-linux-gnu/bin/ld: error: libgtkd-3.o: relocation R_386_GOTOFF against preemptible symbol _D3std3uni__T21genericDecodeGraphemeVbi0Z__TQBfTAxaZQBnFNaNfKQnZv cannot be used when making a shared object
/usr/x86_64-pc-linux-gnu/bin/ld: error: libgtkd-3.o: relocation R_386_GOTOFF against preemptible symbol _D3std3uni__T21genericDecodeGraphemeVbi0Z__TQBfTAxaZQBnFNaNfKQnZv cannot be used when making a shared object

Using ldc2 or gdc as compilers it seems to work, so I assume it is a dmd backend issue. Just the other day a bug in ld.gold got fixed that prevented --ifc=safe to work (e.g. when self-hosting ldc2), --gc-sections got fixed in dmd earlier and this is now the only remaining linker compatibility issue I see on Linux.

!!!There are attachements in the bugzilla issue that have not been copied over!!!

[dlangBugzillaToGithub]

Marco.Leise commented on 2018-04-28T13:38:57Z

Created attachment 1689
small reproduction case for the linker error

I attached a test case that can be compiled with dmd 2.079.1 like this:

    dmd -m32 -shared -fPIC -defaultlib=phobos2 reprocase.d

ld.gold has to be your default linker, otherwise you need to split compilation and linking:

    dmd -m32 -fPIC -c reprocase.d
    ld.gold -shared reprocase.o

What I found interesting about the test case is that it happens when you create a sufficiently complex switch-case. Remove one case and the error is gone. Could it be a bug in jump table generation on x86/PIC ?

[dlangBugzillaToGithub]

Marco.Leise commented on 2018-04-28T13:43:14Z

My guess was hitting close:

    https://github.com/dlang/dmd/blob/1a05f4413ac6daaa8ae000dbe7399a302e3fc16b/src/dmd/backend/cod3.c#L1360

Above three cases a different code path is chosen in the back-end.

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bugzilla (@WalterBright) commented on 2020-05-16T05:49:25Z

Can you show a piece of DMD code that, when compiled, uses a different location than GDC does (or even gcc) ?