#8935: Obscure linker bug leads to crash in GHCi -------------------------------------+------------------------------------ Reporter: simonmar | Owner: simonmar Type: bug | Status: new Priority: high | Milestone: 7.8.3 Component: Runtime System | Version: 7.8.1-rc2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Unknown/Multiple Type of failure: GHCi crash | Difficulty: Rocket Science Test Case: | Blocked By: Blocking: | Related Tickets: -------------------------------------+------------------------------------ Comment (by dagit): I haven't tested if I have the crash on my system, but suspect you're seeing something to do with weak symbols. On my system, Fedora 19, I see that glibc defines environ as a weak symbol and gives it the same address that your libgmp check reports. I modified your C program slightly so that it takes the paths in `argv[1]` and `argv[2]`: {{{ $ ./check-environ /usr/lib64/libgmp.so /usr/lib64/libpthread.so environ = 0x601058 dlsym(deflt, "environ") = 0x601058 dlsym("libgmp", "environ") = 0x31e45bd508 dlsym("libpthread", "environ") = 0x601058 }}} My libgmp doesn't define environ so it must find it in libc, and indeed: {{{ $ readelf -Wa /usr/lib64/libc.so.6 | grep environ 00000031e45b9dd8 0000011900000006 R_X86_64_GLOB_DAT 00000031e45bd508 _environ + 0 00000031e45b9ea0 0000050000000006 R_X86_64_GLOB_DAT 00000031e45bd508 __environ + 0 281: 00000031e45bd508 8 OBJECT WEAK DEFAULT 33 _environ@@GLIBC_2.2.5 956: 00000031e45bd508 8 OBJECT WEAK DEFAULT 33 environ@@GLIBC_2.2.5 1280: 00000031e45bd508 8 OBJECT GLOBAL DEFAULT 33 __environ@@GLIBC_2.2.5 349: 00000031e45bbe70 8 OBJECT LOCAL DEFAULT 33 last_environ 1813: 0000000000000000 0 FILE LOCAL DEFAULT ABS environ.c 4539: 00000031e4238a10 1122 FUNC LOCAL DEFAULT 12 __add_to_environ 5707: 00000031e45bd508 8 OBJECT WEAK DEFAULT 33 _environ 6374: 00000031e45bd508 8 OBJECT GLOBAL DEFAULT 33 __environ 6483: 00000031e45bd508 8 OBJECT WEAK DEFAULT 33 environ }}} I suspect that the way you're searching for the symbol needs to look for a (the?) strong binding first. I hope that helps. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8935#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler