Your message dated Wed, 18 Jul 2018 23:19:21 +0000
with message-id <[email protected]>
and subject line Bug#904055: fixed in ghc 8.2.2-5
has caused the Debian Bug report #904055,
regarding ghc: Please backport important fix for unregisterised compiler
to be marked as done.
This means that you claim that the problem has been dealt with.
If this is not the case it is now your responsibility to reopen the
Bug report if necessary, and/or fix the problem forthwith.
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--
904055: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=904055
Debian Bug Tracking System
Contact [email protected] with problems
--- Begin Message ---
Source: ghc
Version: 8.2.2-4
Severity: normal
Tags: patch upstream
User: [email protected]
Usertags: m68k
Hi!
I recently reported a GHC bug upstream which resulted in miscompiled
code when using an unregisterised compiler [1]. Upstream has managed
to track down the issue to GHC producing code that the C compiler
doesn't like. The bug was observed on m68k and sh4 in Debian, but
according to upstream, can affect any other target using an unregisterised
compiler.
The patch can be found in [2], I'm also attaching it. It would be
highly appreciated if the patch could be included in the next upload
so that future uploads of GHC 8.2.x will continue to work on the
affected architectures.
Thanks,
Adrian
> [1] https://ghc.haskell.org/trac/ghc/ticket/15338
> [2]
> https://git.haskell.org/ghc.git/commitdiff/8ec48990fee9e245bb2fe40dc6f65b61b8612157
--
.''`. John Paul Adrian Glaubitz
: :' : Debian Developer - [email protected]
`. `' Freie Universitaet Berlin - [email protected]
`- GPG: 62FF 8A75 84E0 2956 9546 0006 7426 3B37 F5B5 F913
Description: driver: skip -Bsymbolic on unregisterised targets
Trac #15338 is yet another example where -Bsymbolic breaks
semantics of a C program: global variable duplication happens
and unsafePerformIO creates two stdout copies.
.
When -Bsymbolic is not used both C compiler and linker agree
on how global variables are handled. In case of sh4 it consists
on a few assertions:
.
1. global variable is exported from shared library
2. code is referred to this variable via GOT-like mechanism to allow
interposition
3. global variable is present .bss section on an executable
(as an R_*_COPY relocation: symbol contents is copied at executable
startup time)
4. and symbol in executable interposes symbol in shared library.
.
This way both code in shared library and code in executable refer
to a copy of global variable in .bss section of an executable.
.
Unfortunately -Bsymbolic option breaks assumption [2.] and generates
direct references to the symbol. This causes mismatch between
values seen from executable and values seen from shared library code.
.
This change disables '-Bsymbolic' for unregisterised targets.
--- ghc-8.2.2.orig/compiler/main/SysTools.hs
+++ ghc-8.2.2/compiler/main/SysTools.hs
@@ -1741,9 +1741,12 @@ linkDynLib dflags0 o_files dep_packages
-------------------------------------------------------------------
let output_fn = case o_file of { Just s -> s; Nothing -> "a.out"; }
+ unregisterised = platformUnregisterised (targetPlatform dflags)
let bsymbolicFlag = -- we need symbolic linking to resolve
- -- non-PIC intra-package-relocations
- ["-Wl,-Bsymbolic"]
+ -- non-PIC intra-package-relocations for
+ -- performance (where symbolic linking works)
+ -- See Note [-Bsymbolic assumptions by GHC]
+ ["-Wl,-Bsymbolic" | not unregisterised]
runLink dflags (
map Option verbFlags
@@ -1800,3 +1803,27 @@ getFrameworkOpts dflags platform
-- reverse because they're added in reverse order from the cmd line:
framework_opts = concat [ ["-framework", fw]
| fw <- reverse frameworks ]
+
+{-
+Note [-Bsymbolic assumptions by GHC]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+GHC has a few assumptions about interaction of relocations in NCG and linker:
+
+1. -Bsymbolic resolves internal references when the shared library is linked,
+ which is important for performance.
+2. When there is a reference to data in a shared library from the main program,
+ the runtime linker relocates the data object into the main program using an
+ R_*_COPY relocation.
+3. If we used -Bsymbolic, then this results in multiple copies of the data
+ object, because some references have already been resolved to point to the
+ original instance. This is bad!
+
+We work around [3.] for native compiled code by avoiding the generation of
+R_*_COPY relocations.
+
+Unregisterised compiler can't evade R_*_COPY relocations easily thus we disable
+-Bsymbolic linking there.
+
+See related Trac tickets: #4210, #15338
+-}
--- End Message ---
--- Begin Message ---
Source: ghc
Source-Version: 8.2.2-5
We believe that the bug you reported is fixed in the latest version of
ghc, which is due to be installed in the Debian FTP archive.
A summary of the changes between this version and the previous one is
attached.
Thank you for reporting the bug, which will now be closed. If you
have further comments please address them to [email protected],
and the maintainer will reopen the bug report if appropriate.
Debian distribution maintenance software
pp.
Clint Adams <[email protected]> (supplier of updated ghc package)
(This message was generated automatically at their request; if you
believe that there is a problem with it please contact the archive
administrators by mailing [email protected])
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA512
Format: 1.8
Date: Wed, 18 Jul 2018 18:56:46 -0400
Source: ghc
Binary: ghc ghc-prof ghc-doc
Architecture: source
Version: 8.2.2-5
Distribution: unstable
Urgency: medium
Maintainer: Debian Haskell Group
<[email protected]>
Changed-By: Clint Adams <[email protected]>
Description:
ghc - The Glasgow Haskell Compilation system
ghc-doc - Documentation for the Glasgow Haskell Compilation system
ghc-prof - Profiling libraries for the Glasgow Haskell Compilation system
Closes: 904055
Changes:
ghc (8.2.2-5) unstable; urgency=medium
.
* Apply patch to disable -Bsymbolic on unregisterised
architectures. closes: #904055.
* Add autopkgtest.
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