#4244: Use system linker in GHCi to support alpha, ia64, ppc64
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Reporter: batterseapower | Owner:
Type: feature request | Status: new
Priority: normal | Component: GHCi
Version: 6.13 | Keywords:
Testcase: | Blockedby:
Os: Unknown/Multiple | Blocking:
Architecture: Unknown/Multiple | Failure: None/Unknown
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Sergei Trofimovich says:
{{{
> AFAIK the current linker is meant to support Mach O, ELF and COFF,
> which should cover almost every platform GHC is able to run on. Now,
> it's not ideal that GHC maintains its own dynamic linker
> implementation, but if someone has discovered a bugs with it (or any
> other bug preventing TH from working) I'm sure GHC HQ would be
> interested in knowing.
Unfortunately, GHC itself not just 'dlopen's shared objects. It loads them
by pieces manually setting up relocations (see makeSymbolExtra by link
below).
Each operating system on certaion $ARCH defines it's own ELF spec, which
consists of two parts:
1. common part. platform agnostic (byte sex, byte width, symbol string
table,
section flags, dynamic section attributes and etc.)
2. platform dependant. certain section types, such as TOC sections
(ppc64),
are implemented to solve some certain architecture constraints. You
cannot
program them "in advance".
$ grep PPC64 /usr/include/elf.h
will show way more fun things to be implemented for perfect .so
support.
The best thing to make sure is to look at the real support for ELF in
ghci:
Please, look at file ghc/rtc/Linker.c and function
do_Elf_Rela_relocations()
http://darcs.haskell.org/cgi-
bin/darcsweb.cgi?r=ghc;a=headblob;f=/rts/Linker.c
Conclusion: having ELF aware system is not enough to have ghci support in
any form.
Practically, current gentoo supports ghci on:
i386, amd64, ppc32, sparc(i'm unsure)
and does not support it on:
alpha, ia64, ppc64
Ideally, GHC (and haddock as a result) should support 'ghci'less template-
haskell support
at least on platforms w/o ghci.
Or alternatively haddock could be buildable on 'ghci'less GHC.
It could ignore template-haskell statements (anyway you will not be able
to build
'TH'ful source on such platform)
}}}
See also #3445 #3654 and Simon's email at http://www.haskell.org/pipermail
/cvs-ghc/2009-November/051196.html
So we need to reuse the system linker or extend our custom one to catch
all the cases we see in the wild.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4244>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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