Shared libraries produced by GHC can't see libffi libraries

[ocharles]

Example:

[ollie@io:~]$ cat Test.hs
module Foo where
five = 5

[ollie@io:~]$ ghc -o test.so -c -shared -fPIC -dynamic --make Test.hs -lHSrts_debug-ghc7.6.3
Linking test.so ...

[ollie@io:~]$ ldd test.so
    linux-vdso.so.1 (0x00007fff5c5fe000)
    libHSrts_debug-ghc7.6.3.so => /nix/store/xq36g6s6gy2ww14pqaspvm6ma98n6dc3-ghc-7.6.3/lib/ghc-7.6.3/libHSrts_debug-ghc7.6.3.so (0x00007fa499304000)
    libHSbase-4.6.0.1-ghc7.6.3.so => /nix/store/xq36g6s6gy2ww14pqaspvm6ma98n6dc3-ghc-7.6.3/lib/ghc-7.6.3/base-4.6.0.1/libHSbase-4.6.0.1-ghc7.6.3.so (0x00007fa498a17000)
    libHSinteger-gmp-0.5.0.0-ghc7.6.3.so => /nix/store/xq36g6s6gy2ww14pqaspvm6ma98n6dc3-ghc-7.6.3/lib/ghc-7.6.3/integer-gmp-0.5.0.0/libHSinteger-gmp-0.5.0.0-ghc7.6.3.so (0x00007fa498805000)
    libgmp.so.10 => /nix/store/xhi96qw8i4ms3q1z1grh6jsgwgz3sm4i-gmp-5.0.5/lib/libgmp.so.10 (0x00007fa49858d000)
    libHSghc-prim-0.3.0.0-ghc7.6.3.so => /nix/store/xq36g6s6gy2ww14pqaspvm6ma98n6dc3-ghc-7.6.3/lib/ghc-7.6.3/ghc-prim-0.3.0.0/libHSghc-prim-0.3.0.0-ghc7.6.3.so (0x00007fa498319000)
    libc.so.6 => /nix/store/zm4bhsm8lprkzvrjgqr0klfkvr21als4-glibc-2.17/lib/libc.so.6 (0x00007fa497f69000)
    libffi.so.6 => not found
    libm.so.6 => /nix/store/zm4bhsm8lprkzvrjgqr0klfkvr21als4-glibc-2.17/lib/libm.so.6 (0x00007fa497c6a000)
    librt.so.1 => /nix/store/zm4bhsm8lprkzvrjgqr0klfkvr21als4-glibc-2.17/lib/librt.so.1 (0x00007fa497a62000)
    libdl.so.2 => /nix/store/zm4bhsm8lprkzvrjgqr0klfkvr21als4-glibc-2.17/lib/libdl.so.2 (0x00007fa49785d000)
    /nix/store/zm4bhsm8lprkzvrjgqr0klfkvr21als4-glibc-2.17/lib64/ld-linux-x86-64.so.2 (0x00007fa499798000)
    libpthread.so.0 => /nix/store/zm4bhsm8lprkzvrjgqr0klfkvr21als4-glibc-2.17/lib/libpthread.so.0 (0x00007fa497641000)

[ollie@io:~]$ ghc -o test.so -c -shared -fPIC -dynamic --make Test.hs -lHSrts_debug-ghc7.6.3 -lffi
Linking test.so ...

[ollie@io:~]$ ldd test.so
    linux-vdso.so.1 (0x00007ffff97fe000)
    libHSrts_debug-ghc7.6.3.so => /nix/store/xq36g6s6gy2ww14pqaspvm6ma98n6dc3-ghc-7.6.3/lib/ghc-7.6.3/libHSrts_debug-ghc7.6.3.so (0x00007f12790a8000)
    libffi.so.6 => /nix/store/xq36g6s6gy2ww14pqaspvm6ma98n6dc3-ghc-7.6.3/lib/ghc-7.6.3/libffi.so.6 (0x00007f1278e9a000)
    libHSbase-4.6.0.1-ghc7.6.3.so => /nix/store/xq36g6s6gy2ww14pqaspvm6ma98n6dc3-ghc-7.6.3/lib/ghc-7.6.3/base-4.6.0.1/libHSbase-4.6.0.1-ghc7.6.3.so (0x00007f12785ae000)
    libHSinteger-gmp-0.5.0.0-ghc7.6.3.so => /nix/store/xq36g6s6gy2ww14pqaspvm6ma98n6dc3-ghc-7.6.3/lib/ghc-7.6.3/integer-gmp-0.5.0.0/libHSinteger-gmp-0.5.0.0-ghc7.6.3.so (0x00007f127839b000)
    libgmp.so.10 => /nix/store/xhi96qw8i4ms3q1z1grh6jsgwgz3sm4i-gmp-5.0.5/lib/libgmp.so.10 (0x00007f1278123000)
    libHSghc-prim-0.3.0.0-ghc7.6.3.so => /nix/store/xq36g6s6gy2ww14pqaspvm6ma98n6dc3-ghc-7.6.3/lib/ghc-7.6.3/ghc-prim-0.3.0.0/libHSghc-prim-0.3.0.0-ghc7.6.3.so (0x00007f1277eb0000)
    libc.so.6 => /nix/store/zm4bhsm8lprkzvrjgqr0klfkvr21als4-glibc-2.17/lib/libc.so.6 (0x00007f1277aff000)
    libm.so.6 => /nix/store/zm4bhsm8lprkzvrjgqr0klfkvr21als4-glibc-2.17/lib/libm.so.6 (0x00007f1277801000)
    librt.so.1 => /nix/store/zm4bhsm8lprkzvrjgqr0klfkvr21als4-glibc-2.17/lib/librt.so.1 (0x00007f12775f9000)
    libdl.so.2 => /nix/store/zm4bhsm8lprkzvrjgqr0klfkvr21als4-glibc-2.17/lib/libdl.so.2 (0x00007f12773f4000)
    /nix/store/zm4bhsm8lprkzvrjgqr0klfkvr21als4-glibc-2.17/lib64/ld-linux-x86-64.so.2 (0x00007f127953c000)
    libpthread.so.0 => /nix/store/zm4bhsm8lprkzvrjgqr0klfkvr21als4-glibc-2.17/lib/libpthread.so.0 (0x00007f12771d8000)

[edolstra]

The reason is that libHSrts_debug-ghc7.6.3.so lacks a proper RPATH:

# ldd /nix/store/xq36g6s6gy2ww14pqaspvm6ma98n6dc3-ghc-7.6.3/lib/ghc-7.6.3/libHSrts_debug-ghc7.6.3.so
        linux-vdso.so.1 (0x00007fffde198000)
        libffi.so.6 => not found
        libm.so.6 => /nix/store/zm4bhsm8lprkzvrjgqr0klfkvr21als4-glibc-2.17/lib/libm.so.6 (0x00007fe475c0f000)
        librt.so.1 => /nix/store/zm4bhsm8lprkzvrjgqr0klfkvr21als4-glibc-2.17/lib/librt.so.1 (0x00007fe475a06000)
        libdl.so.2 => /nix/store/zm4bhsm8lprkzvrjgqr0klfkvr21als4-glibc-2.17/lib/libdl.so.2 (0x00007fe475802000)
        libc.so.6 => /nix/store/zm4bhsm8lprkzvrjgqr0klfkvr21als4-glibc-2.17/lib/libc.so.6 (0x00007fe475452000)
        libpthread.so.0 => /nix/store/zm4bhsm8lprkzvrjgqr0klfkvr21als4-glibc-2.17/lib/libpthread.so.0 (0x00007fe475235000)
        /nix/store/zm4bhsm8lprkzvrjgqr0klfkvr21als4-glibc-2.17/lib64/ld-linux-x86-64.so.2 (0x00007fe4761a0000)

So applications that link against libHSrts_debug-ghc7.6.3.so will fail unless they explicitly link against libffi themselves.

This suggests that GHC should be built with NIX_LDFLAGS set to -rpath $out/lib/ghc-<version> or something like that.

(Ping @peti, @kosmikus)

[peti]

There is a whole bunch of Haskell-related improvements in stdenv-updates that would be nice to have in master -- including this one. When I get the chance, I'll try to merge those patches into master separately, so that we can have those improvements soon.