Fix minimum alignment for StgClosure (Trac #11395)
The bug is observed on m68k-linux target as crash in RTS: -- a.hs: main = print 43 $ inplace/bin/ghc-stage1 --make -debug a.hs $ ./a Program terminated with signal SIGSEGV, Segmentation fault. #0 0x80463b0a in LOOKS_LIKE_INFO_PTR_NOT_NULL (p=32858) at includes/rts/storage/ClosureMacros.h:248 (gdb) bt #0 0x80463b0a in LOOKS_LIKE_INFO_PTR_NOT_NULL (p=32858) at includes/rts/storage/ClosureMacros.h:248 #1 0x80463b46 in LOOKS_LIKE_INFO_PTR (p=32858) at includes/rts/storage/ClosureMacros.h:253 #2 0x80463b6c in LOOKS_LIKE_CLOSURE_PTR ( p=0x805aac6e <stg_dummy_ret_closure>) at includes/rts/storage/ClosureMacros.h:258 #3 0x80463e4c in initStorage () at rts/sm/Storage.c:121 #4 0x8043ffb4 in hs_init_ghc (...) at rts/RtsStartup.c:181 #5 0x80455982 in hs_main (...) at rts/RtsMain.c:51 #6 0x80003c1c in main () GHC assumes last 2 pointer bits are tags on 32-bit targets. But here 'stg_dummy_ret_closure' address violates the assumption: LOOKS_LIKE_CLOSURE_PTR (p=0x805aac6e <stg_dummy_ret_closure>) I've added compiler hint for static StgClosure objects to align closures at least by their natural alignment (what GHC assumes). See Note [StgWord alignment]. Signed-off-by:Sergei Trofimovich <siarheit@google.com> Test Plan: ran basic test on m68k qemu, it got past ASSERTs Reviewers: simonmar, austin, bgamari Reviewed By: bgamari Subscribers: thomie Differential Revision: https://phabricator.haskell.org/D1974 GHC Trac Issues: #11395
Loading
Please register or sign in to comment