#14675: GHC 8.4.1 regression: segfault when loading doctest on a module with ANNs on Ubuntu 16.04 or later -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: bgamari Type: bug | Status: new Priority: highest | Milestone: 8.4.1 Component: GHC API | Version: 8.4.1-alpha1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: Runtime crash | Test Case: Blocked By: | Blocking: Related Tickets: #14603 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonmar): Ok, I think I have a bit more info on this, and a better workaround. For me the crash happened here: {{{ (gdb) disassemble 0x0000000040792900,0x0000000040792910 Dump of assembler code from 0x40792900 to 0x40792910: 0x0000000040792900: mov 0x10(%rbp),%rax 0x0000000040792904: mov %rbx,%rcx 0x0000000040792907: and $0x7,%ecx => 0x000000004079290a: jmpq *0x403ff568(,%rcx,8) }}} and the memory at 0x403ff568 looks bogus. By using `+RTS -Dl` and digging through the logs, correlating this with `objdump --reloc HSbase-4.11.0.0.o`, I got that this relocation is: {{{ 00000000004228cd R_X86_64_32S .rodata-0x0000000000451cd8 }}} which is utterly bogus: we should never have a negative offset into a section. The original object file, before it was squashed into `HSbase-4.11.0.0.o` has this: {{{ 0000000000000b3d R_X86_64_32S .rodata..LneLq }}} which is a sensible relocation to the unique section name `.rodata..LneLq`. Looks like something has gone wrong when we squashed the object files together to make `HSBase-4.11.0.0.o`. Indeed, if I take the command line to squash the object files and replace `ld.gold` with `ld`, then I get this relocation: {{{ 00000000004228cd R_X86_64_32S .rodata+0x000000000000e158 }}} which is much more sensible. And after doing that, the crashing program now works. So this suggests that the workaround should be to avoid using `ld.gold` for squashing objects together, I'll make a diff. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14675#comment:22 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler