[GHC] #11315: GHC doesn't restore split objects
#11315: GHC doesn't restore split objects -------------------------------------+------------------------------------- Reporter: snowleopard | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.3 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- While working on the new Shake-based build system I came across an annoying problem related to missing split objects ([#note see note]). I still don't fully understand the reasons behind the problem, but I found that GHC doesn't restore missing split objects, as explained in the example below. I think this is a bug, but maybe this is actually a missing feature. I think it shouldn't be difficult to fix. {{{#!hs module Test (test) where test :: Int test = 0 }}} I compile the above with `ghc -split-objs Test.hs` and get two split object files in `Test_o_split`. Then if I delete any of these files, or even the whole folder, and rerun `ghc -split-objs Test.hs` the compiler doesn't bother to restore split objects, pretending that everything is up- to-date. However, if I delete `Test.o` all object files are restored. Another related issue reported by Neil Mitchell (which may be worth a separate ticket) is that even if we corrupt `Test.o` and rerun `ghc -split-objs Test.hs`, the compiler doesn't restore the object file (nor missing split objects) to the consistent state. ---- [=#note Note:] The problem I have is described here: https://github.com/snowleopard/shaking-up-ghc/issues/30. It's not necessary to follow the link to understand this ticket, however I'd appreciate any insight you might have about the reasons behind the problem and/or a possible solution. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11315 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#11315: GHC doesn't restore split objects -------------------------------------+------------------------------------- Reporter: snowleopard | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.3 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by ezyang): The problem is, even though `A_o_split` is supposed to be considered output of compilation, the recompilation checkers for `--make` and `-c` (the ones that determine if the source is modified) only look at the merged `o` file (not the split objects) to see if they've gone away. Distressingly, in the current scheme, it is unobvious whether or not a split object directory is complete or not. So this suggests that we have to atomically output some digest describing all of the split objects we expect to see. Recompilation avoidance, when running in split objects mode, checks to see if the digest is newer than the source file, and that all the files in the digest exist. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11315#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#11315: GHC doesn't restore split objects -------------------------------------+------------------------------------- Reporter: snowleopard | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.3 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by thomie): I was hoping we could get rid of `-split-objs`, now that #8405 is implemented (function-sections). -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11315#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#11315: GHC doesn't restore split objects -------------------------------------+------------------------------------- Reporter: snowleopard | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.3 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by snowleopard): Replying to [comment:2 thomie]:
I was hoping we could get rid of `-split-objs`, now that #8405 is implemented (function-sections). Interesting. We can certainly experiment with function sections in the new build system, but as I understand we still need to provide full support for split objects.
-- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11315#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#11315: GHC doesn't restore split objects
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Reporter: snowleopard | Owner: (none)
Type: bug | Status: new
Priority: normal | Milestone:
Component: Compiler | Version: 7.10.3
Resolution: | Keywords:
Operating System: Unknown/Multiple | Architecture:
| Unknown/Multiple
Type of failure: None/Unknown | Test Case:
Blocked By: | Blocking:
Related Tickets: | Differential Rev(s):
Wiki Page: |
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Comment (by Marge Bot
#11315: GHC doesn't restore split objects -------------------------------------+------------------------------------- Reporter: snowleopard | Owner: (none) Type: bug | Status: closed Priority: normal | Milestone: 8.10.1 Component: Compiler | Version: 7.10.3 Resolution: fixed | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by bgamari): * status: new => closed * resolution: => fixed * milestone: => 8.10.1 -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11315#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#11315: GHC doesn't restore split objects -------------------------------------+------------------------------------- Reporter: snowleopard | Owner: (none) Type: bug | Status: closed Priority: normal | Milestone: 8.10.1 Component: Compiler | Version: 7.10.3 Resolution: fixed | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by bgamari): `-split-objs` has been removed in favor of `-split-sections`. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11315#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
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