#3333: GHCi doesn't load weak symbols
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Reporter: heatsink | Owner:
Type: bug | Status: new
Priority: normal | Milestone: 6.14.1
Component: GHCi | Version: 6.10.4
Keywords: weak, dynamic loading | Difficulty: Unknown
Os: Linux | Testcase:
Architecture: x86 | Failure: None/Unknown
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Comment(by heatsink):
> It would be easy to add weak symbols to the symbol table, but I'm not
sure what the correct semantics should be. Perhaps weak symbols should be
subordinated to global (STB_GLOBAL) and local (STB_LOCAL) symbols. Is this
sufficient? (I haven't studied the documentation yet.)
Weak symbols are never unified with local symbols. Probably it's an error
to have a weak and a local symbol with the same name in the same file. I
don't know what this means in terms of GHC's linker.
> Question: Is it possible to have the same weak symbol defined in more
than one module? If so, how does the linker choose?
Yes. AFAICT the choice is arbitrary. GCC's linker's choice depends on
the order that files are listed on the command line. It is at least
necessary to consider SHN_UNDEF when selecting a weak symbol (defined weak
symbols take precedence over undefined weak symbols).
The following statement from the ELF document appears to be relevant, but
I don't know what extracting archive members has to do with symbol
resolution.
> The link editor does ''not'' extract archive members to resolve undeļ¬ned
weak symbols.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/3333#comment:7>
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