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