#6107: GHCi runtime linker cannot link with duplicate common symbols
--------------------------+-------------------------------------------------
Reporter: exFalso | Owner:
Type: bug | Status: new
Priority: normal | Component: Compiler
Version: 7.4.1 | Keywords:
Os: Linux | Architecture: Unknown/Multiple
Failure: None/Unknown | Testcase:
Blockedby: | Blocking:
Related: |
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GHCi's runtime linker reports duplicate common symbols as fatal error.
According to the nm manual: "When linking, multiple common symbols may
appear with the same name".
This means that for example one cannot link using the FFI with libraries
having multiple common symbols if TH splices are used.
To illustrate let's create two object files both defining the same common
symbol:
commonSym.c
{{{
volatile commonSym;
}}}
{{{
$ gcc -o commonSym.o commonSym.c -c
$ gcc -o commonSym2.o commonSym.c -c
$ nm commonSym.o commonSym2.o
commonSym.o:
0000000000000004 C commonSym
commonSym2.o:
0000000000000004 C commonSym
}}}
Now we create two dummy .hs files, one having a TH splice which (i'm
guessing) triggers the runtime linker.
Works.hs
{{{
module Works where
}}}
DoesntWork.hs
{{{
{-# LANGUAGE TemplateHaskell #-}
module DoesntWork where
$(return [])
}}}
{{{
$ ghc Works.hs commonSym.o commonSym2.o
[1 of 1] Compiling Works ( Works.hs, Works.o )
$ ghc DoesntWork.hs commonSym.o commonSym2.o
[1 of 1] Compiling DoesntWork ( DoesntWork.hs, DoesntWork.o )
Loading package ghc-prim ... linking ... done.
Loading package integer-gmp ... linking ... done.
Loading package base ... linking ... done.
Loading object (static) commonSym.o ... done
Loading object (static) commonSym2.o ...
GHCi runtime linker: fatal error: I found a duplicate definition for
symbol
commonSym
whilst processing object file
commonSym2.o
(...)
}}}
Just to make sure that this -should- link:
works.c
{{{
extern commonSym;
int main (void)
{
int _ = commonSym;
}
}}}
{{{
$ gcc -o works.o works.c -c
$ nm works.o
U commonSym
0000000000000000 T main
$ gcc -o works works.o commonSym.o commonSym2.o
$ ./works ; echo $?
0
}}}
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/6107>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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