[GHC] #1066: MacOSX powerpc gcc 3.3/4.0 and unknown symbol `_printf$LDBLStub'

[GHC]

#1066: MacOSX powerpc gcc 3.3/4.0 and unknown symbol `_printf$LDBLStub'
--------------------------------+-------------------------------------------
 Reporter:  gracjan-agh.edu.pl  |          Owner:  thorkilnaur
     Type:  bug                 |         Status:  new        
 Priority:  normal              |      Milestone:  6.6.1      
Component:  Compiler            |        Version:  6.6        
 Severity:  minor               |     Resolution:             
 Keywords:                      |     Difficulty:  Easy (1 hr)
 Testcase:                      |   Architecture:  powerpc    
       Os:  MacOS X             |  
--------------------------------+-------------------------------------------
Comment (by thorkilnaur):

 The basic problem as far as I am able to understand is that GHC has been
 built on a system using gcc-4.0 and is now being used on a system with
 gcc-3.3. Being built using gcc-4.0 means that some of the libraries, in
 particular libHSrts.a, contain references to these $LDBLStub-suffixed
 standard C library entry points. For example:
 {{{
 Thorkil-Naurs-Computer:~/tn/GHC/trac/1066/base thorkilnaur$ nm
 /Users/thorkilnaur/tn/install/ghc-HEAD-for-1066-
 20070211_1657/lib/ghc-6.7.20070209/libHSrts.a
 ...
 /Users/thorkilnaur/tn/install/ghc-HEAD-for-1066-
 20070211_1657/lib/ghc-6.7.20070209/libHSrts.a(StackOverflow.o):
   00000000 T _StackOverflowHook
          U ___sF
          U _fprintf$LDBLStub
          U dyld_stub_binding_helper
 ...
 Thorkil-Naurs-Computer:~/tn/GHC/trac/1066/base thorkilnaur$
 }}}

 So when linking with gcc-3.3, errors result:

 {{{
 Thorkil-Naurs-Computer:~/tn/GHC/trac/1066/base thorkilnaur$ cat t2.hs
 module Main where
   main = putStr ("t2: Hello trac 1066 2007-Feb-17 19.48\n")
 Thorkil-Naurs-Computer:~/tn/GHC/trac/1066/base thorkilnaur$ ghc --version
 The Glorious Glasgow Haskell Compilation System, version 6.7.20070209
 Thorkil-Naurs-Computer:~/tn/GHC/trac/1066/base thorkilnaur$ gcc --version
 powerpc-apple-darwin8-gcc-4.0.1 (GCC) 4.0.1 (Apple Computer, Inc. build
 5250)
 Copyright (C) 2005 Free Software Foundation, Inc.
 This is free software; see the source for copying conditions.  There is NO
 warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR
 PURPOSE.

 Thorkil-Naurs-Computer:~/tn/GHC/trac/1066/base thorkilnaur$ ghc -fforce-
 recomp -pgml gcc-3.3 --make t2.hs
 [1 of 1] Compiling Main             ( t2.hs, t2.o )
 Linking t2 ...
 ld: Undefined symbols:
 _sprintf$LDBLStub
 _fprintf$LDBLStub
 _vfprintf$LDBLStub
 _sscanf$LDBLStub
 Thorkil-Naurs-Computer:~/tn/GHC/trac/1066/base thorkilnaur$
 }}}

 Whereas if we stay with gcc-4.0, all is well:

 {{{
 Thorkil-Naurs-Computer:~/tn/GHC/trac/1066/base thorkilnaur$ ghc -fforce-
 recomp --make t2.hs
 [1 of 1] Compiling Main             ( t2.hs, t2.o )
 Linking t2 ...
 Thorkil-Naurs-Computer:~/tn/GHC/trac/1066/base thorkilnaur$
 }}}

 So far, I have just repeated what the original reporter of this problem
 has done.

 When getting to the easy work-around, however, I must admit that it took
 me a while to find it. Simply adding -lSystemStubs to the ghc command is
 not sufficient:

 {{{
 Thorkil-Naurs-Computer:~/tn/GHC/trac/1066/base thorkilnaur$ ghc -fforce-
 recomp -pgml gcc-3.3 --make t2.hs -lSystemStubs
 [1 of 1] Compiling Main             ( t2.hs, t2.o )
 Linking t2 ...
 ld: Undefined symbols:
 _sprintf$LDBLStub
 _fprintf$LDBLStub
 _vfprintf$LDBLStub
 _sscanf$LDBLStub
 Thorkil-Naurs-Computer:~/tn/GHC/trac/1066/base thorkilnaur$
 }}}

 One possibility is to use the ghc -v option to get a listing of the link
 command and then add -lSystemStubs to the end of that. Another possibility
 is to "guess" that HSrts is the library that needs these symbols and add
 -lHSrts before the -lSystemStubs:

 {{{
 Thorkil-Naurs-Computer:~/tn/GHC/trac/1066/base thorkilnaur$ ghc -fforce-
 recomp -pgml gcc-3.3 --make t2.hs -lHSrts -lSystemStubs
 [1 of 1] Compiling Main             ( t2.hs, t2.o )
 Linking t2 ...
 Thorkil-Naurs-Computer:~/tn/GHC/trac/1066/base thorkilnaur$
 }}}

 And that actually works.

 So what to do about this? I must admit, Wolfgang, that I don't really see
 how the fix that you propose would work: It seems to be a change in the
 GHC build process, but the difference between gcc versions is apparent
 only in the GHC user's environment. And this could be entirely different
 if the user had installed a binary GHC.

 Specifically, you seem to propose something that will wire this
 !SystemStubs library into the GHC installation. If that is correctly
 understood and !SystemStubs, as I interpret it, provides a bridge from
 gcc-4.0 compiled code to gcc-3.3 libraries, how would the resulting GHC
 work in an environment entirely without gcc 3.3?

 However, I could very well be off the track here and welcome additional
 comments.

 What I propose to do presently is to write a GHC FAQ entry about the
 matter and then close this ticket with resolution wontfix. After all, the
 work-around does not seem particularly more difficult than the technique
 described in the User's Guide section "Options affecting linking"
 http://www.haskell.org/ghc/docs/latest/html/users_guide/options-
 phases.html#options-linker to ensure that the HSrts library main()
 function is used, rather than some other main() function defined in the
 code.

 And, again, additional comments on this matter would be most welcome.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/1066>
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