SevenThunders wrote:

I have a large Haskell/C project that needs to be linked against an even larger set of C libraries and object files (OpNet) on a linux box (Fedora Core 7). So far I have been able to link my Haskell libraries to some C test code containing a main function without incident. However the link flags are very complex having been extracted from ghc. (e.g. it requires a host of -u flags and then a bunch of links to external C libraries including a long list of Haskell libraries.)

Unfortunately control over the OpNet compilation and linking process is weak at best. Moreover it is not clear how the linking occurs and there is some suspicion that it ultimately creates a dynamic link library which it loads from some external process (the exact calls to gcc are hidden). During the OpNet build we get the following error

/usr/lib/ghc-6.6.1/libHSrts.a(Main.o): In function `main': Main.c:(.text+0x22): undefined reference to `__stginit_ZCMain' Main.c:(.text+0x43): undefined reference to `ZCMain_main_closure' collect2: ld returned 1 exit status

I do not get this error when statically linking my libraries to a standalone C function containing a main() function. What should I look for? Are there known work arounds to this problem? It's troubling that exporting Haskell to C should be this problematic. Unfortunately I can not use ghc to compile the OpNet code as you might imagine.

Does this error occur because of dynamic linking? That is if this were all packed into some library without a main function in C it would try to link to the Main.o object file in libHSrts.a, which has some unsatisfied links since there is no main function in the Haskell code. So does static linking always fix this? Is it possible to fix it by providing a dummy main function in a dynamic link library? I don't know if the latter is possible in linux. -- View this message in context: http://www.nabble.com/GHC-linking-problems-tf4270650.html#a12171221 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.

Did I find a bug cabal? I have attempted to fix the problem Main.c:(.text+0x22): undefined reference to `__stginit_ZCMain' by compiling my Haskell library using the flag -no-hs-main. One would think that this would make sense if the library is to be used by an external C program. However I am using cabal to build the haskell library and I immediately run into a problem. My netsim.cabal file looks like Name: Netsim Version: 1.1 License: AllRightsReserved Exposed-modules: Matrix, Parsefile, PowCDF Build-Depends: base, regex-compat>=0.71, parsec>=2.0 Extensions: ForeignFunctionInterface Includes: matrixstack.h Install-includes: matrixstack.h, TunePerf.h Include-dirs: ../matrixstack, /usr/lib/ghc-6.6.1/include, . Extra-libraries: netsimc, matrixstack, lapack, ptcblas, atlas Extra-lib-dirs: /usr/local/atlas/lib, ., ./phymake,../matrixstack Ghc-options: -fglasgow-exts -O2 -no-hs-main My setup.hs file looks like: import Distribution.Simple main = defaultMainWithHooks defaultUserHooks When I build this using runhaskell Setup.hs build all the source files compile just fine, but then a screwy thing happens. Cabal attempts to build an executable called a.out. Moreover a.out has no main of course and it does not attempt to link to any of the libraries in the Extra-libraries field. This kills the cabal build. So trying to link a.out (which it shouldnt be doing) gives me the errors, Preprocessing library Netsim-1.1... Building Netsim-1.1... Linking a.out ... dist/build/Matrix.o: In function `Netsimzm1zi1_Matrix_zdwccall_info': ghc6835_0.hc:(.text+0x1ea9): undefined reference to `PmatC' dist/build/Matrix.o: In function `Netsimzm1zi1_Matrix_zdwccall1_info': ghc6835_0.hc:(.text+0x1f79): undefined reference to `Pmat' dist/build/Matrix.o: In function `Netsimzm1zi1_Matrix_zdwccall2_info': ... /usr/lib/ghc-6.6.1/libHSrts.a(Main.o): In function `main': Main.c:(.text+0x22): undefined reference to `__stginit_ZCMain' Main.c:(.text+0x43): undefined reference to `ZCMain_main_closure' If I eliminate the -no-hs-main flag in Ghc-options no attempt is made to creat a.out, which is as it should be and the library builds without complaint. This seems like a bug in cabal. -- View this message in context: http://www.nabble.com/GHC-linking-problems-tf4270650.html#a12206722 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.