hrmmm, i seem to recall it being said that you need to use the GOLD linker on ARM. (i think some of this is detailed in http://bgamari.github.io/posts/2014-03-06-compiling-ghc-7.8-on-arm.html  )

 ,("ld command","arm-poky-linux-gnueabi-ld") 
is that GOLD?


On Tue, Jul 8, 2014 at 1:51 AM, Michael Jones <mike@proclivis.com> wrote:
I am pasting both the info from the HOST and TARGET compilers:

HOST
====

 [("Project name","The Glorious Glasgow Haskell Compilation System")
 ,("GCC extra via C opts"," -fwrapv")
 ,("C compiler command","/usr/bin/gcc")
 ,("C compiler flags"," -fno-stack-protector  -Wl,--hash-size=31 -Wl,--reduce-memory-overheads")
 ,("ar command","/usr/bin/ar")
 ,("ar flags","q")
 ,("ar supports at file","YES")
 ,("touch command","touch")
 ,("dllwrap command","/bin/false")
 ,("windres command","/bin/false")
 ,("perl command","/usr/bin/perl")
 ,("target os","OSLinux")
 ,("target arch","ArchX86_64")
 ,("target word size","8")
 ,("target has GNU nonexec stack","True")
 ,("target has .ident directive","True")
 ,("target has subsections via symbols","False")
 ,("LLVM llc command","llc")
 ,("LLVM opt command","opt")
 ,("Project version","7.6.3")
 ,("Booter version","7.6.3")
 ,("Stage","2")
 ,("Build platform","x86_64-unknown-linux")
 ,("Host platform","x86_64-unknown-linux")
 ,("Target platform","x86_64-unknown-linux")
 ,("Have interpreter","YES")
 ,("Object splitting supported","YES")
 ,("Have native code generator","YES")
 ,("Support SMP","YES")
 ,("Unregisterised","NO")
 ,("Tables next to code","YES")
 ,("RTS ways","l debug  thr thr_debug thr_l thr_p dyn debug_dyn thr_dyn thr_debug_dyn thr_debug_p")
 ,("Leading underscore","NO")
 ,("Debug on","False")
 ,("LibDir","/usr/lib/ghc")
 ,("Global Package DB","/usr/lib/ghc/package.conf.d")
 ,("Gcc Linker flags","[\"-Wl,--hash-size=31\",\"-Wl,--reduce-memory-overheads\"]")
 ,("Ld Linker flags","[\"--hash-size=31\",\"--reduce-memory-overheads\"]")
 ]


TARGET
=======

 [("Project name","The Glorious Glasgow Haskell Compilation System")
 ,("GCC extra via C opts"," -fwrapv")
 ,("C compiler command","arm-poky-linux-gnueabi-gcc")
 ,("C compiler flags"," -fno-stack-protector")
 ,("C compiler link flags","")
 ,("ld command","arm-poky-linux-gnueabi-ld")
 ,("ld flags","")
 ,("ld supports compact unwind","YES")
 ,("ld supports build-id","YES")
 ,("ld supports filelist","NO")
 ,("ld is GNU ld","YES")
 ,("ar command","/usr/bin/ar")
 ,("ar flags","q")
 ,("ar supports at file","YES")
 ,("touch command","touch")
 ,("dllwrap command","/bin/false")
 ,("windres command","/bin/false")
 ,("libtool command","libtool")
 ,("perl command","/usr/bin/perl")
 ,("target os","OSLinux")
 ,("target arch","ArchARM {armISA = ARMv5, armISAExt = [], armABI = HARD}")
 ,("target word size","4")
 ,("target has GNU nonexec stack","False")
 ,("target has .ident directive","True")
 ,("target has subsections via symbols","False")
 ,("Unregisterised","NO")
 ,("LLVM llc command","llc")
 ,("LLVM opt command","opt")
 ,("Project version","7.8.2")
 ,("Booter version","7.6.3")
 ,("Stage","1")
 ,("Build platform","x86_64-unknown-linux")
 ,("Host platform","x86_64-unknown-linux")
 ,("Target platform","arm-unknown-linux")
 ,("Have interpreter","YES")
 ,("Object splitting supported","NO")
 ,("Have native code generator","NO")
 ,("Support SMP","YES")
 ,("Tables next to code","YES")
 ,("RTS ways","l debug thr thr_debug thr_l  ")
 ,("Support dynamic-too","YES")
 ,("Support parallel --make","YES")
 ,("Dynamic by default","NO")
 ,("GHC Dynamic","NO")
 ,("Leading underscore","NO")
 ,("Debug on","False")
 ,("LibDir","/usr/local/lib/arm-unknown-linux-gnueabi-ghc-7.8.2")
 ,("Global Package DB","/usr/local/lib/arm-unknown-linux-gnueabi-ghc-7.8.2/package.conf.d")
 ]




On Jul 7, 2014, at 10:42 PM, Carter Schonwald <carter.schonwald@gmail.com> wrote:

could you share the output of ghc --info?


On Tue, Jul 8, 2014 at 12:10 AM, Michael Jones <mike@proclivis.com> wrote:
I am having problems building a GHC cross compiler for Linux (Yocto on a Wandboard) running on a Cortex A9, and need some advice on how to debug it.

The cross compiler produces an executable that runs on the Target, but fails to print. So I need help coming up with a strategy to narrow down the root cause.

Some details:

The application:

main = do
    putStrLn "Haskell start"


The command line options work. The program runs, and I can step through assembly. Debug data is printed to the console. But putStrLn fails, and program enters an infinite loop.

I compile my app as follows:

arm-unknown-linux-gnueabi-ghc -debug -static Main.hs

Using -threaded does not fix the problem.

Let me compare debug data from a run on my HOST, with a run on my TARGET. First, a run from my HOST:

created capset 0 of type 2
created capset 1 of type 3
cap 0: initialised
assigned cap 0 to capset 0
assigned cap 0 to capset 1
cap 0: created thread 1
cap 0: running thread 1 (ThreadRunGHC)
cap 0: thread 1 stopped (suspended while making a foreign call)
cap 0: running thread 1 (ThreadRunGHC)
cap 0: thread 1 stopped (finished)
cap 0: created thread 2
cap 0: running thread 2 (ThreadRunGHC)
cap 0: thread 2 stopped (finished)
cap 0: starting GC
cap 0: GC working
cap 0: GC idle
cap 0: GC done
cap 0: GC idle
cap 0: GC done
cap 0: GC idle
cap 0: GC done
cap 0: GC idle
cap 0: GC done
cap 0: all caps stopped for GC
cap 0: finished GC
removed cap 0 from capset 0
removed cap 0 from capset 1
cap 0: shutting down
deleted capset 0
deleted capset 1

And, it prints properly. So this is my referenced for what it should do on the TARGET.

When I run on my TARGET, I get:

created capset 0 of type 2
created capset 1 of type 3
cap 0: initialised
assigned cap 0 to capset 0
assigned cap 0 to capset 1
cap 0: created thread 1
cap 0: running thread 1 (ThreadRunGHC)
cap 0: thread 1 stopped (yielding)
cap 0: running thread 1 (ThreadRunGHC)
cap 0: thread 1 stopped (yielding)
cap 0: running thread 1 (ThreadRunGHC)
cap 0: thread 1 stopped (yielding)
cap 0: running thread 1 (ThreadRunGHC)
cap 0: thread 1 stopped (yielding)
cap 0: running thread 1 (ThreadRunGHC)
cap 0: thread 1 stopped (yielding)
cap 0: running thread 1 (ThreadRunGHC)
cap 0: thread 1 stopped (yielding)
cap 0: running thread 1 (ThreadRunGHC)
cap 0: thread 1 stopped (stack overflow)
cap 0: running thread 1 (ThreadRunGHC)
cap 0: thread 1 stopped (stack overflow)
cap 0: running thread 1 (ThreadRunGHC)
cap 0: thread 1 stopped (stack overflow)
cap 0: running thread 1 (ThreadRunGHC)
cap 0: thread 1 stopped (yielding)
cap 0: running thread 1 (ThreadRunGHC)
cap 0: thread 1 stopped (stack overflow)
cap 0: running thread 1 (ThreadRunGHC)
cap 0: thread 1 stopped (stack overflow)
cap 0: running thread 1 (ThreadRunGHC)
cap 0: thread 1 stopped (stack overflow)
cap 0: running thread 1 (ThreadRunGHC)
cap 0: thread 1 stopped (yielding)
cap 0: running thread 1 (ThreadRunGHC)
cap 0: thread 1 stopped (stack overflow)
cap 0: running thread 1 (ThreadRunGHC)
cap 0: thread 1 stopped (heap overflow)
cap 0: starting GC
cap 0: GC working
cap 0: GC idle
cap 0: GC done
cap 0: GC idle
cap 0: GC done
cap 0: GC idle
cap 0: GC done
cap 0: all caps stopped for GC
cap 0: finished GC
cap 0: running thread 1 (ThreadRunGHC)
cap 0: thread 1 stopped (yielding)
cap 0: running thread 1 (ThreadRunGHC)
cap 0: thread 1 stopped (stack overflow)
...

And the debug data goes on forever, just as debugging assembly demonstrated an infinite loop.

Clearly, the following does not occur:

cap 0: thread 1 stopped (suspended while making a foreign call)

And there are overflows.

If I had to guess, it is possible that some code is in a loop retrying to foreign call, and failing. Certainly, it is in some kind of a loop, because I found a place I can put a break point and and telling GDB to continue will cause the break over and over at the same place. So somewhere there is a loop.

I can step through the application with GDB and see names of files and offsets in assembly. But without a true source code debug, that is a bit rough, especially for someone that does not know the RTS code. If there was a way to compile such that C source code was available and a place to break, that would help. However, I suspect since it never makes a foreign call, there is no place in C to place the breakpoint anyway. So I am also assuming there is no direct way to debug with GDB.

But, I can see debug output printed to the console. My hope is there is a way to enable more printing, or a place I can add more print functions to help find the problem.

So I think I need one of the following:

- A solution from someone that has seen this before, perhaps on the iPhone
- How to enable more debug logging
- Where in the source code to add debug statements to narrow down the problem

Thanks for any help you can give.

Mike


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