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-prof -fPIC -fexternal-dynamic-refs generates non-PIC relocations for external symbol

    • Closed Issue created by Zejun Wu @watashi

    When compiling code with -prof -fPIC -fexternal-dynamic-refs, the generated object file may contains R_X86_64_PC32 relocation to symbols defined in another object file.

    $ cat T15723A.hs T15723B.hs
module T15723A where

{-# INLINE foo #-}
foo :: Int -> Int
foo x = {-# SCC foo1 #-} bar x

{-# NOINLINE bar #-}
bar :: Int -> Int
bar x = x
module T15723B where

import T15723A

test :: Int -> Int
test x = {-# SCC test1 #-} foo $ foo x
$ $HC -prof -prof -fPIC -fexternal-dynamic-refs -O2 -c T15723A.hs
$ $HC -prof -prof -fPIC -fexternal-dynamic-refs -O2 -c T15723B.hs
$ objdump -rdS T15723B.o | less
0000000000000028 <T15723B_test_info>:
  28:   48 8d 45 f0             lea    -0x10(%rbp),%rax
  2c:   4c 39 f8                cmp    %r15,%rax
  2f:   72 70                   jb     a1 <T15723B_test_info+0x79>
  31:   48 83 ec 08             sub    $0x8,%rsp
  35:   48 8d 35 00 00 00 00    lea    0x0(%rip),%rsi        # 3c <T15723B_test_info+0x14>
                        38: R_X86_64_PC32       T15723B_test1_EXPR_cc-0x4
  3c:   49 8b bd 60 03 00 00    mov    0x360(%r13),%rdi
  43:   31 c0                   xor    %eax,%eax
  45:   e8 00 00 00 00          callq  4a <T15723B_test_info+0x22>
                        46: R_X86_64_PLT32      pushCostCentre-0x4
  4a:   48 83 c4 08             add    $0x8,%rsp
  4e:   48 ff 40 30             incq   0x30(%rax)
  52:   49 89 85 60 03 00 00    mov    %rax,0x360(%r13)
  59:   48 83 ec 08             sub    $0x8,%rsp
  5d:   48 8d 35 00 00 00 00    lea    0x0(%rip),%rsi        # 64 <T15723B_test_info+0x3c>
                        60: R_X86_64_PC32       T15723A_foo1_EXPR_cc-0x4

    When attempt to link both T15723A.o and T15723B.o in ghci using +RTS -xp, the address of T15723A_foo1_EXPR_cc can be more than 2G away from T15723B_test_info and cause link error or segfault.

    Edited
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